ABSTRACTS
TWENTY-SEVENTH PACIFIC CLIMATE WORKSHOP
Asilomar State Conference Grounds,
Pacific Grove, California
March 8-11th 2015
PACLIM is a multidisciplinary workshop that broadly addresses the climatic phenomena
occurring in the eastern Pacific Ocean and western North America. The purpose of the
workshop is to understand climate effects in this region by bringing together specialists
from diverse fields including physical, social, and biological sciences. Time scales from
weather to the Quaternary are addressed in oral and poster presentations.
The theme of the 2015 PACLIM workshop addresses the issue of drought: How we
develop long term records of drought, how we monitor drought and how we predict
drought. The remainder of the meeting is devoted to a wide range of climate-related
topics.
The atmosphere of the workshop is intentionally informal, and room and board are
provided for many of the participants. This year, the workshop was organized by faculty
from Sonoma State University, and the University of Nevada, Reno with support from
representatives of the U.S. Geological Survey. The funding and other sources of
support come from several agencies:
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The Desert Research Institute: Alan Gertler
The U.S. Geological Survey Climate and Land Use Change Research &
Development Program: Debra Willard
The University of Nevada, Reno: Frank Fanelli and Daniel Fergus, Teaching
Learning Technologies
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Evening Speakers Biographies
Laura Cunningham
Artist-Naturalist
Laura Cunningham is an artist-naturalist who has worked in the field of wildlife biology.
Trained in paleontology at the University of California at Berkeley (B.S.), and in natural
science illustration at UC Santa Cruz (Graduate Certificate), Cunningham has brought
her skills to a diverse set of scientific projects: working with the United States Geological
Survey Biological Resource Division analyzing amphibian declines in the Sierra Nevada
and amassing species inventories in Death Valley National Park; the California
Department of Fish and Game restoring habitats of pupfish, tui chub, trout, Steelhead,
monitoring Tule elk in the Owens Valley, and studying mountain lion predation; with
California State University, Dominguez Hills, Cunningham worked in conservation
biology and genetic studies involving Desert tortoises, Panamint alligator lizards, and
Mojave fringe-toed lizards.
Cunnigham has been a scientific illustrator for the Museum of Paleontology at University
of California, Berkeley and illustrated fossil invertebrates for the Smithsonian Institution,
Washington, D.C. She has also produced mural exhibits for various museums and
institutions, including scenes of fossil mammals at Badlands National Park, and murals
depicting the history of life on Earth for the California State University Fresno
Department of Earth and Environmental Sciences. Her work has also been exhibited at
numerous art shows and museums around the country, including the Pacific Rim
Wildlife Art Show in Seattle, the Oakland Museum, Santa Barbara Museum of Natural
History, Denver Museum of Nature and Science, Carnegie Museum, and Safari Club
International.
The book "A State of Change" on the historical ecology of California was published by
Heyday in 2010.
Currently, Cunningham is studying the historical ecology of the California deserts and
Nevada Great Basin, and co-founded a desert conservation organization-- Basin &
Range Watch.
~*~
Sandi Matsumoto
Associate Director, Integrated Water Management, The Nature Conservancy
Sandi Matsumoto leads a multi-disciplinary team to ensure that California operates it
surface and groundwater storage and conveyance systems collectively and proactively
to meet the needs of nature as well as the needs of people. Prior to this role, tackled
local and regional water management issues, focusing on providing wetlands for
migratory birds and on protecting floodplain for steelhead in southern California. In the
past two years, she led the Migratory Bird team to launch BirdReturns, an innovative
program that uses precision science to identify what bird habitat is needed, when and
where, and then selects participants through a reverse auction. The results demonstrate
that providing annual incentive payments can be a cost-effective complement to
3
permanent protection. During her ten years with the Conservancy, she helped acquire
almost 2,000 acres of wetlands and floodplains that serve as habitat for native species.
Prior to joining the Conservancy, she developed affordable housing and interned for the
Aspen Institute and United Nations. A Central Valley native, she earned her B.A. in
economics from Yale University and spent a term at the University of Cape Town while
earning her M.B.A. from the UCLA Anderson School of Management.
~*~
Paclim 2015 Abstracts
Links between San Lazaro Basin carbonate productivity and Western North
America mega-droughts
Jose Abella-Gutiérreza and Juan Carlos Hergueraa
aDivision
Oceanología, CICESE, Carretera Ensenada-Tijuana No. 3918, Zona Playitas,
ZIP 22860, Ensenada, B.C. México. joseluisabella@gmail.com
Here we present results from a reconstruction based on biogenic sediment records of
several box and kasten cores retrieved form San Lázaro Basin (SLB), a suboxic basin
located in the southern dynamic boundary of the California Current System (CCS),
characteristic for its high sedimentation rates (1mm/yr). The downcore variability of
carbonate in this basin is mainly controlled by the export and preservation of
coccolithophorids in the sediment record. This phytoplankton group seems to be most
abundant during periods of water column stratification and when nutrients are still
available within the light penetration depth in the water columna. These relatively warm
and stratified conditions in the water column, occur when tropical and subropical waters
invades the Gulf of Ulloa from the south all the way up north to Punta Eugenia. The
intrusion of these water masses shows a large degree of variability for different time
scales,ranging from seasonal to millennial, and several factors may be involved and
interrelated; i) The relaxation of equatorward winds.. ii) the variability associated to
ENSO-like conditions iii) The migration of the ITCZ. All these factors exert an important
influence in the precipitation regime of the western North America continent and are
responsible for the development of large droughts across the South West North
America (SWNA).
The carbonate spectrum analysis shows significant decadal and interdecadal periods
that correlate with the instrumental record and the different indexes that capture large
scale climate and ocean dyanmics (PDO, SST, NINO3.4) and relatively short-term
paleo records (Biondi's PDO, Winter Upwelling, Galapagos Coral). Comparisons
between the carbonate record from SLB and other paleoclimatic records of the last 2
Kyr variability of carbonates show large similarities with low frequencies of the DAI from
SWNA (Cook et al., 2004) and the position of the ITCZ (%Ti, Haug et al., 2001). In SLB
carbonates, a 110-120 y peak explain the largest variability of the record and coincides
with a similar frequency mode from the DAI. When the variance of this mode is
considered, similarities arise with intensity and number of ENSO events from Equatorial
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archives. We will discuss the implications of these periods in the carbonate record and
its relation with the drought records in North America.
~*~
Reconstructing Holocene paleoproductivity along the northern California
continental shelf
Jason A. Addison a, John Barron a, Bruce Finney b, John P. McGeehin c, and Clark R.
Alexander, Jr. d
aU.S.
Geological Survey, Menlo Park, CA 94025 (jaddison@usgs.gov;
jbarron@usgs.gov); b Depts. of Geological & Biological Sciences, Idaho State
University, Pocatello, ID 83209-8007 (finney@isu.edu); c US Geological Survey,
Reston, VA 20192 (mcgeehin@usgs.gov); d Skidaway Institute of Oceanography,
Savannah, GA 31411 (clark.alexander@skio.uga.edu)
The Holocene paleoceanographic history of the northern California continental shelf is
examined in this study using the high-resolution record of TN062-O550 (40.9°N,
124.6°W, 550 m water depth). This 7-m-long marine sediment core spans
approximately 7800 to 200 cal yr BP, and we use it to test the hypothesis that marine
productivity in the California Current upwelling system has co-varied with changes in
Holocene productivity across the broader North Pacific Ocean. Analysis of biogenic
sediment concentrations (opal, TOC), organic matter δ13C, and sedimentary δ15N were
used to test this hypothesis. A preliminary age model, calculated with CLAM (v.2.2;
Blaauw, 2010) and based on three planktic foraminiferal 14C dates combined with
stratigraphic projections of four additional dates from adjacent shelf cores (<10 km
distant), produced a median error of ~167 years per cm. This temporal precision is
sufficient to resolve multi-centennial timescales.
Biogenic silica (opal) concentrations show significant millennial-scale step increases at
~4700 and ~3300 cal yr BP, culminating in the highest opal concentrations during the
late Holocene. The same trend is seen in organic matter δ13C (e.g., depleted values
during the early Holocene that become progressively more enriched into the late
Holocene), supporting the interpretation that the opal increase is a function of increased
diatom productivity and δ13C changes reflect nutrient uptake (CO2 [aq]), and not a
change in sedimentation rate. Bulk sedimentary δ15N values follow this same three-step
pattern, increasing from 4.27±0.35‰ during the period >4700 cal yr BP (n=28), to
4.64±0.22‰ between 4700-3300 cal yr BP (n=13), and culminating at 4.72±0.24‰ at
<3300 cal yr BP (n=37). These differences are significant at the 95% confidence level
and are within the expected ranges for phytoplankton nitrate uptake. There is also a
highly significant correlation between organic matter δ13C and sedimentary δ15N (n = 84,
r = 0.80, p < 0.01), indicating a strong coupling between macronutrient dynamics and
productivity.
Blauw, M., 2010, Methods and code for ‘classical’ age-modeling of radiocarbon
sequences. Quaternary Geochronology 5, 512-518.
~*~
5
California hydroclimate monitoring in the 21st Century
Michael L. Anderson
California Department of Water Resources 3310 El Camino Avenue Room 200,
Sacramento, CA 95821 (Michael.L.Anderson@water.ca.gov)
California possesses an amazingly variable and diversified climate. Monitoring that
climate and the hydrology that results is also highly variable and diversified. Multiple
agencies have multiple networks focused on different aspects of the hydroclimate
system for specific purposes. An example is the State’s Cooperative Snow Surveys
automated snow pillow sites used to forecast water supply runoff between April and
July. To that end, these networks may not be positioned to track changes in key
variables associated with climate change. A look at the multitude of monitoring
networks and the data sets developed will be provided. Gaps in the monitoring
networks for observing and tracking a changing climate will be identified. Options and
future prospects for filling those gaps will then be outlined. Areas of potential future
research will also be discussed.
~*~
Do high-elevation lakes record variations in snowfall and atmospheric rivers in
the Sierra Nevada of California?
Jacob E. Ashforda, James O. Sickmana, and Delores M. Luceroa
aDepartment
of Environmental Sciences, University of California, Riverside, Riverside,
CA 92507 (jacob.ashford@email.ucr.edu)
Understanding the underlying causes of interannual variation in snowfall and extreme
hydrologic events in the Sierra Nevada is hampered by short instrumental records and
the difficulties in reconstructing climate using a traditional paleo-record such as treerings. New paleo proxies are needed to provide a record of snowpack water content and
extreme precipitation events over millennial timescales which can be used to test
hypotheses regarding teleconnections between Pacific climate variability and water
supply and flood risk in California. In October 2013 we collected sediment cores from
Pear Lake (z = 27 m), an alpine lake in Sequoia National Park. The cores were split and
characterized by P-wave velocity, magnetic susceptibility and density scanning.
Radiocarbon dates indicate that the Pear Lake cores contain a 13.5K yr record of lake
sediment. In contrast to other Sierra Nevada lakes previously cored by our group, highresolution scanning revealed alternating light-dark bands (~1 mm to 5 mm thick) for
most of the Pear Lake core length. This pattern was interrupted at intervals by
homogenous clasts (up to 75 mm thick) ranging in grain size from sand to gravel up to 1
cm diameter. We hypothesize that the light-dark banding results from the breakdown of
persistent hypolimnetic anoxia during spring snowmelt and autumn overturn. We
speculate that the thicknesses of the dark bands are controlled by the duration of anoxia
which in turn is controlled by the volume and duration of snowmelt. The sand to gravel
sized clasts are most likely associated with extreme precipitation events resulting from
atmospheric rivers intersecting the southern Sierra Nevada. We hypothesize that
6
centimeter-sized clasts are deposited in large avalanches and that the sands are
deposited in large rain events outside of the snow-cover period.
~*~
Surface water conditions in the Gulf of California during the Medieval Climate
Anomaly and Little Ice Age
John Barrona, Dave Bukrya, Jason Addisona
aU.S.
Geological Survey, MS 910, Menlo Park, CA 94025 (jbarron@usgs.gov,
dbukry@usgs.gov, jaddison@usgs.gov)
High-resolution analyses of diatoms, silicoflagellates, and percent opal in laminated
sediment cores from the Guaymas Basin (central Gulf of California) reveal pronounced
changes in surface water conditions over the past 2000 years. Prior to ~ AD 1200,
surface waters in the western Guaymas Basin (boxcore MD02-2517c2 at 27.4850° N,
112.0743°W, water depth 887 m) were characterized by high biologic productivity
marked by alternating relative abundances of the diatoms Thalassionema nitzschioides
and Fragilariopsis doliolus and the silicoflagellates Octactis pulchra and Dictyocha
stapedia. Following the early part of the Medieval Climate Anomaly (MCA; ~AD 8001200), productivity declined abruptly in two steps (at ~AD 1200 and ~1500). This shift
was marked by increases in the relative abundance of tropical diatoms (Azpeitia
nodulifera) and silicoflagellates (Dictyocha perlaevis). The western Guaymas record
thus resembles that of the eastern North Pacific (equatorial Pacific and Santa Barbara
Basin) with a cooler La Niña-like early MCA followed by a warmer El Niño-like Little Ice
Age (LIA; ~AD 1350-1850).
In contrast, in the eastern Guaymas Basin (Kasten Core BAM80 E-17 at 27.920° N,
111.610°W, 620 m of water depth), highly productive conditions dominated the past
2000 years until a post ~ AD 1800 period of surface water warming, which has been
documented throughout the Gulf. Similar to the western Guaymas record, the diatom
assemblage in the eastern Guaymas Basin suggests warmer water during the late MCA
and LIA relative to before ~ AD 1200. Unlike the surface waters to the west, however,
the early MCA (~ AD 800-1200) in the eastern basin is distinguished by a decline in high
productivity diatoms and silicoflagellates. These findings, together with an increase in
tropical diatom taxa, are suggestive of warmer MCA surface water conditions that are
conducive to enhanced transport of monsoonal moisture northward up the axis of the
Gulf.
East-West surface water differences in the Guaymas Basin during the past 2000 years
can be explained by analogy to the modern climatology. Presently, winter upwelling
and biologic productivity are stronger in the east than they are in the west. At the same
time, northward flowing surface currents that transport tropical waters into the basin
during the summer are stronger in the east than they are in the west. These east-west
differences appear to have been especially pronounced during the early MCA (~AD
800-1000).
~*~
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Causes and Implications of late Holocene Drought in the Cuenca Oriental of
Mexico
Tripti Bhattacharyaa Roger Byrnea, Harald Bohnelb, and Kurt Wogaub
a Department
of Geography, University of California, Berkeley, CA (tripti@berkeley.edu)
b Centro
de Geociencias, Universidad Nacional Autónoma de México (U.N.A.M.)
Campus Juriquilla, Queretaro 76230, Mexico
Reconstructing drought in Mesoamerica has important implications for our
understanding of the relationship between cultural developments and climatic change.
Understanding causes of late Holocene climate variability can help improve the
predictability of long-term drought events. Different lines of proxy evidence have been
used to reconstruct drought, including speleothems, tree rings, and lacustrine records,
but records are still sparse from highland Mexico. We present a lacustrine record of late
Holocene drought from the Cuenca Oriental, in the eastern Trans-Mexican Volcanic
Belt. Stable isotopes of authigenic carbonates (δ18O) provide evidence of past changes
in the ratio of precipitation to evaporation (P/E). We use model output and instrumental
data to investigate the climatic processes recorded by this proxy, and to investigate the
causes of long-term drought. Our initial results suggest that, at least in our region of
highland Mexico, the ∂18O signal is most sensitive to changes in summertime rainfall.
Results also suggest a role for the El Nino Southern Oscillation in forcing centennial
scale drought in highland Mexico and across Mesoamerica. We also reconstruct past
changes in vegetation and fire regimes, and discuss the cultural implications of drought
in highland Mexico.
~*~
Drought and Fire in the Klamath Forests of northern California
Christy E. Brilesa, Cathy Whitlockb, and Ali Whiteb
a Department
of Geography and Environmental Science, University of Colorado Denver,
Denver, CO 80217 (christy.briles@ucdenver.edu); bDepartment of Earth Sciences,
Bozeman, MT 59717 (whitlock@montana.edu)
Fire is a dominant and misunderstood ecosystem process in the Klamath forests of
northern California. Dendrochronological studies suggest that fire is governed by the
topographic and climatic heterogeneity of the region and patterns established by past
fires. Using lake sediment records from ten sites in mid-to-high elevation locations we
explore how periods of historical drought have impacted fire regimes and forests. In the
early Holocene (11.5-7ka), when summer insolation was at a maximum and there was
an intensified subtropical high-pressure system, fire activity was more frequent than
today. Forests were dominated by xerophytic conifers of white pines and cedars on nonultramafic substrates and yellow pines and cedars on ultramafic substrates. As summer
insolation declined through the mid Holocene (7-4 ka), so did fire activity, but it
remained more frequent than today. Fir replaced white pines as the dominant conifer in
forests on non-ultramafics, while forests on ultramafics remained unchanged. As
summer insolation continued to decline through the late Holocene (4 ka-present), fire
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activity peaked during the Medieval Climate Anomaly on non-ultramafics. As winter
insolation increase, lower snowpack may have resulted in reduce effective moisture in
summer resulting in greater fire activity. Forests were dominated by fir and Douglas-fir,
and mountain hemlock was abundant in higher elevation forests. On ultramafics, fire
activity decreased, likely due to the loss of the shrub understory. The lowest recorded
fire activity occurred in the last 1000 years on all substrates in response to cool moist
conditions of the Little Ice Age and fire suppression efforts. Within this period two large
fires are recorded at sites in the northern Klamath and southern Cascade Mountains,
suggesting fires were widespread. Climate has been the dominant driver of fire regimes
in the Klamath forests, with periods of drought resulting in higher fire activity regionally,
except when understory fuels were limited.
~*~
A Holocene Record of Vegetation, Fire and the Seasonality of Precipitation for the
Bonneville Basin, USA
Andrea Brunellea, William Eckerleb, Mitch Powera
a
Department of Geography, University of Utah, Salt Lake City, UT 84112
(andrea.brunelle@geog.utah.edu); b Western GeoArch Research, Driggs, ID, 83422
A record of environmental change was reconstructed from a GLAD core collected from
the Great Salt Lake that covers the last 10,000+ years. This record represents a time
period not well-studied for the Bonneville Basin and also represents the first
sedimentary record of fire from this region. Multiple proxy were used to reconstruct the
environmental history that include charcoal, pollen, magnetic susceptibility, diatoms,
grain size, loss-on-ignition and macrofossil analysis. Ratios of the pollen from
vegetation types sensitive to winter versus summer precipitation were used to
reconstruct changes moisture in general as well as changes in the seasonality of
precipitation. Distinctive changes in vegetation composition and fire regime were
identified that were consistent with reconstructed changes in the variability in the
amounts and seasonality of precipitation.
~*~
Simulated megadroughts over California and the global response of the isotopic
composition of precipitation
Nikolaus H. Buenninga and Lowell D. Stotta
Department of Earth Sciences, University of Southern California, Los Angeles, CA
(buenning@usc.edu)
Reconstructions of hydroclimate variability in the western US document episodes of
prolonged drought referred to as “megadroughts”. The air-sea interactions that lead to
megadroughts are not well constrained. In this study we evaluate how sea surface
temperature (SST) anomalies influence the stable isotopic composition atmospheric
moisture at times of drought and investigate how the stable isotopic composition from
proxies can be used to assess what SST patterns produced past megadroughts. Based
on 9 ensemble simulations of the free-running isotope-incorporated Global Spectral
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Model (IsoGSM), we identified robust correlation patterns between surface temperature
anomalies and protracted dry and wet periods in California. The most robust SST
anomalies that correlate with dry periods include a PDO-like pattern in the North Pacific;
La Niña-like SSTs in the tropical Pacific; and a warm tropical Atlantic Ocean. These
SST anomaly patterns are used to force additional IsoGSM simulations. The simulations
were run for 40 years with reoccurring monthly SSTs that contain no interannual
variations. We find that neither the North Pacific nor the Tropical Pacific anomalies
alone produces protracted dryness in California that is statistically different than the
control simulation with no SST anomalies. However, when the two Pacific anomalies
were applied together, the model produced a distinct 40-year drought over multiple
ensemble simulations. These same experiments simulated distinct isotope anomaly
fields in atmospheric moisture that are indicative of the SST anomalies associated with
drought. Isotope proxies (tree cellulose and speleothem calcite) from key regions may
be used to reconstruct SST anomaly patterns that were responsible for periods of
megadrought in the past. These isotopic signatures should be compared to recent
isotopic changes to determine if the current drought affecting the western US is uniquely
different than past megadroughts.
~*~
Drought and climate variability influences on quaking aspen (Populus
tremuloides) in the Intermountain West
Vachel A. Cartera, Andrea Brunellea, Tom A. Minckleyb
aDepartment
of Geography, University of Utah, Salt Lake City, UT 84112
(vachel.carter@gmail.com); bDepartment of Geography, University of Wyoming, Laramie, WY
Quaking aspen (Populus tremuloides) is the most widely distributed deciduous tree in
the subalpine ecotone in North America. Recent decline of aspen stands in the western
United States has been hypothesized to be a result of conifer replacement, fire
suppression and/or warming temperatures. Recent management activities aim for
conservation targets within an ecosystems natural range of variability. However,
conservation targets for quaking aspen rely on 20th century trends. Kulakowski et al.
(2004) suggest the 20th century may not represent the full range of variability of aspen
dynamics and that the current decline could be within the longer natural range of
variability. To examine the full range of variability, this research examines a unique
‘Populus period’ between 3,600 and 3,900 cal yr BP, when a lodgepole pine (Pinus
contorta) dominated system transitioned to a mixed forest dominated by quaking aspen
with lodgepole pine. The study site, Long Lake, is located in the Medicine Bow range of
southeastern Wyoming. Long Lake is currently dominated by lodgepole pine with the
quaking aspen ecotone boundary ~30 m downslope. The Populus period occurs ~300
years after the ‘Mega Drought’ centered around 4,200 cal yr BP (Booth et al., 2005),
and occurs ~100 years after a proposed global climate re-organization centered around
4,000 cal yr BP (Liu et al., 2014). The objectives of this research are to examine the
influences of the ‘Mega Drought’ on quaking aspen populations and the hypothesized
climate re-organization centered around 4,000 cal yr BP. Preliminary results suggest an
increase in winter moisture, associated with the proposed climate re-organization, and
an increase in fire activity frequency created favorable conditions for the upslope
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migration of quaking aspen at Long Lake. Preliminary results also suggest the ‘Mega
Drought’ had little influence on the Populus period. Understanding the full range of
natural variability within the quaking aspen system is important for land managers and
their conservation targets, especially in the wake of future climate predictions for
western North America.
~*~
A 50,000 Year Record of Wildfires in the North Coast Ranges: Microscopic
Charcoal Evidence from Clear Lake, California
Marie Champagnea, Roger Byrneb, David Wahlc, and Cynthia Looyd
a UC
Berkeley, Department of Geography, 507 McCone Hall, Berkeley, CA 94720
(vformarie@gmail.com); b UC Berkeley, Department of Geography, 507 McCone Hall,
Berkeley, CA 94720 (arbyrne@berkeley.edu); c United States Geological Survey, 345
Middlefield Road, Menlo Park, CA 94025-3561 (dwahl@usgs.gov);
d UC Berkeley, Department of Integrative Biology, 3060 Valley Life Sciences Building,
Berkeley, CA 94720 (looy@berkeley.edu)
Here we report on the microscopic charcoal content of the upper section (0.00 m to
69.00 m) of a long core recovered by DOSECC from Clear Lake in 2012. Charcoal was
encountered in all the samples analyzed but is generally small in size presumably
reflecting the distance of the core site from the shoreline (minimum 2 km). The core
section is well dated by a series of 21 pollen-concentrate AMS dates and an identified
ash layer, the Olema Ash at 63.20 m. The portion of the core analyzed for charcoal
covers the period 54,000 BP to the present. Microscopic charcoal was counted on
slides prepared for pollen analysis using standard techniques. Lycopodium spores and
Zea pollen were added to each sample as controls. The sizes of charcoal pieces were
recognized and recorded on count sheets. The results indicate major changes in
charcoal accumulation rates in the time period analyzed. Rates were low during the
LGM and late glacial and increased dramatically during the early Holocene.
Accumulation rates during the Holocene varied significantly but were generally high
during the period 11,500 through 5,500 BP.
We interpret the low LGM and late glacial accumulation rates to be a result of cool
summers and atmospheric stability. Increased moisture availability in summer due to
reduced evaporation and/or increased precipitation was probably also important. Higher
charcoal accumulation rates during the late glacial and Holocene are most likely the
result of increased seasonality of rainfall and temperature, and in particular, the
development of the summer drought regime. We see no clear evidence of increased
burning due to human activity although historical evidence from the contact period
clearly demonstrates that it was ecologically important.
~*~
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Climatic influences on seasonal precipitation from northern Baja California, a
~44,000 yr palaeoenvironmental record
Vanessa Chaveza, and Andrea Brunellea
aUniversity
of Utah, 260 S. Central Campus Dr., Rm. 270, Salt Lake City, UT, 84112,
vanessa.chavez@umail.edu
The desert ecosystem of southwestern North America is driven by a combination of
oceanic and atmospheric patterns and is sensitive to changes within the climate system.
Much of the research in this region has concentrated on identifying moisture sources via
these oceanic and atmospheric patterns in order to understand what the dominant
climate patterns have been over time. Since the late Pleistocene, evidence for
increased winter and/or summer precipitation is highly variable across spatial scales.
This study analyzes two desert wetland sites (Ciénega Chimeneas-CC12A, 32o 14’ N
and 116 o 06’ W, and Ciénega San Faustino-CSF12A, 32° 12’ 30.4” N 116° 09’ 55” W)
located in the Sierra de Juarez to help define when and where changes in the
seasonality of precipitation have occurred over the last ~44,000 cal yr BP and how
changes in the available moisture sources have influenced this region’s climate and
landscape over this time. Today, CC12A and CSF12A are ephemerally active ciénegas
but radiocarbon dating suggests that for at least the last ~6,000 cal yrs BP climate has
either been too dry or too variable for continuous sedimentation to occur at either site, a
timing that corresponds with documented increases in El Niño Southern Oscillation
activity and a fluctuating climate across the region. Fire activity at CC12A decreases
around ~43,000 cal yr BP followed by a period of extremely low sedimentation rates,
indicating aridity at this site. These conditions remain constant until ~33,000 cal yr BP
when sedimentation accumulation increases and the initiation of our CSF12A record
occurs. From ~43,000 until ~14,000 cal yr BP vegetation is largely dominated by shrubs
and herbs. At ~14,000 cal yr BP trees and aquatic plants become more prevalent on the
landscape suggesting some change in the climate system and precipitation patterns
that allow for standing water at these sites.
~*~
Climate change and drought in the Tahoe Basin at millennial to annual time
scales
Robert Coatsa, Goloka Sahooa, Jack Lewisb and Geoffrey Schladowa
aTahoe
bUSDA
Environmental Research Center, Univ. of Calif., Davis, CA 95616
Forest Service (Ret.) Pacific Southwest Res. Sta., Arcata, CA 95521
Lake Tahoe, an iconic ultra-oligotrophic lake in the central Sierra Nevada, has been
studied intensively since 1968, with the goal of understanding and ultimately controlling
its eutrophication and loss of clarity. Research on the lake has included a) periodic
profiles of primary productivity, nutrients, temperature, and plankton; b) Secchi depth; c)
nutrient limitation experiments; d) radiocarbon dating of underwater in-place tree
stumps; e) analysis of long-term temperature trends. Work in the watershed of the
basin has included monitoring of stream discharge, sediment and forms of nitrogen and
phosphorus at up to 20 stream gaging stations.
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At millennial time scales, dated underwater stumps in Tahoe and Fallen Leaf Lake have
provided the basis for tracing possible future shorelines of Lake Tahoe under conditions
of persistent drought, with implications for the future water supply in the Truckee River.
Using a 100-yr climate record for the basin, we found a) increases in daily minimum
temperature and inter-annual variability in precipitation; b) a shift from a snowdominated regime to a rainfall regime; c) increasing inter-annual variability in the Palmer
Drought Severity Index, with the five wettest and five driest summer months all
occurring after 1976. Streamflow records since +/- 1974 show a shift in the timing of
peak snowmelt in 5 streams toward earlier dates of about 0.4 days/yr. Simultaneous
stream chemistry records show downward trends in nitrate-N loads in some streams,
possibly as a result of long-term forest recovery from heavy 19th and 20th century
disturbance. The lake temperature and water quality records indicate a) increasing
temperature and resistance to deep mixing and b) a slight decline (possibly droughtinfluenced) in the trend toward decreasing clarity. Recent climate modeling using
downscaled GCM results has suggested the likelihood of increased droughts, continued
shift from snow to rain, and severe flooding. By linking a lake clarity model and
distributed hydrologic model with the GCM output, we found that deep mixing and
ventilation of the lake may shut down by ca. 2065, triggering a large release of
biostimulatory phosphorus and nitrogen.
~*~
Unprecedented 21st-Century Drought Risk in the American Southwest and
Central Plains
Benjamin I Cooka,b,*, Toby R Aultc, Jason E Smerdonb
Goddard Institute for Space Studies,
2880 Broadway, New York, NY, 10009,
USA (benjamin.i.cook@nasa.gov); bOcean and Climate Physics, Lamont-Doherty Earth
Observatory, 61 Route 9W, Palisades, NY, 10964, USA; cEarth and Atmospheric
Sciences, Cornell University, Ithaca, NY, 14853, USA
aNASA
In the Southwest and Central Plains of Western North America, climate change is
expected to increase drought severity in the coming decades. These regions
nevertheless experienced extended Medieval-era droughts that were more persistent
than any historical event, providing crucial targets in the paleoclimate record for
benchmarking the severity of future drought risks. Here, we use an empirical drought
reconstruction and three soil moisture metrics from 17 state-of-the-art general
circulation models (GCMs) to show that these models project a significantly drier later
half of the 21st-century compared to the 20th-century and earlier paleoclimatic intervals.
This desiccation is consistent across the majority of models regardless of the employed
moisture balance variable, indicating a coherent and robust drying response to warming
despite the diversity of models and metrics analyzed. Notably, future drought risk will
likely exceed even the driest centuries of the Medieval Climate Anomaly (1100–1300
CE) in both moderate (RCP 4.5) and high (RCP 8.5) future emissions scenarios, leading
to drought conditions without precedent during the last millennium.
~*~
13
Forecasting Meteorological Drought Over California Using the North Pacific High
January Anomaly and a Statistical/Dynamical Method
Mariza C. Costa Cabrala, John Rathb, Sujoy B. Royb, William B. Millsb, and Cristina
Milesic
a
Northwest Hydraulic Consultants, Inc., Seattle WA 98188 (mcabral@nhcweb.com); b
Tetra Tech, Inc., R&D Department, Lafayette CA 94549 (Sujoy.roy@tetratech.com); c
Cristina Milesi, NASA Ames Research Center, Moffett Field CA 94035
(cristina.milesi@nasa.gov)
We show that meteorological drought over California can be forecast statistically with
high success rate, using as the predictor the dynamically forecast January sea level
pressure anomaly at the North Pacific High winter climatological location. We show that
the sea-level pressure winter-time anomaly in the North Pacific High provides a superior
predictor of seasonal precipitation totals and extremes over most of California,
compared to traditional ENSO indices such as SOI, MEI, NINO3.4 and others. The NPH
anomaly more closely reflects the effects of ENSO over this region. We show the
effectiveness of the NPH winter anomaly when used in conjunction with atmospheric
humidity (HUS at 850 hPa level) in a statistical model that predicts seasonal
precipitation total, and a statistical model that predicts the likelihood of daily precipitation
extremes. We show how our models can use NPH winter anomaly for precipitation
forecasting and, in an additional application, how it can also be used to derive
precipitation projections based on GCM-projections of NPH and HUS. Large-scale
climatic variables have been used as predictors of precipitation totals and extremes in
many studies and are used operationally in weather forecasts, to circumvent the
difficulty in obtaining robust dynamical simulations of precipitation, which is among the
most complex of all climate variables in its mathematical representation in dynamical
models. The NPH-based statistical models presented here may find useful applications
in drought forecasting, water resources planning, and flood protection planning in
California.
~*~
Using tree-ring isotopes to understand hydroclimate variability in the Upper
Colorado River Basin.
Adam Csanka,c, Connie Woodhouseb,c, Greg Pedersond, John Danloeb, and Steve
Leavittc
aDivision
of Hydrologic Sciences, Desert Research Institute, Reno, NV, 89512
(adam.csank@dri.edu) ; bDepartment of Geography and Regional Development,
University of Arizona, Tucson, AZ, 85721; cLaboratory of Tree Ring Research,
University of Arizona, Tucson, AZ, 85721; dUSGS, Northern Rocky Mountain Science
Center, Bozeman, MT, 59715
14
With recent declines in snowpack, a major water reservoir, in the mountains of
Colorado, there is a need to develop paleoclimate data sets to investigate the climatic
drivers behind snowpack declines and its associated impact on streamflow in the
Colorado River. Recent work indicates that spring temperatures are increasingly
becoming an important driver of snowpack declines in the Southern Rockies. At present
tree-ring records from the Upper Colorado River have been used to provide records of
summer temperature, winter precipitation and streamflow. However the ability to provide
long term proxy records of cool season temperatures and summer precipitation has
eluded dendrochronologists.
Here we have investigated 18O records derived from tree-rings of Douglass-Fir and
piñon pine in western Colorado to assess whether isotopic records derived from treerings can provide climatic information different from that obtained from ring width
indices. We sampled trees at 6 sites in western Colorado, at low, high and mid
elevations. All trees had radial growth that was sensitive to winter precipitaiton and our
sites were chosen to have each of our two species, Douglass-Fir and piñon pine, at
each three different elevations (low, mid, high).
Results show high correlations between low elevation Douglass-Fir 18O and MarchMay temperatures (r = 0.54), whereas high elevation sites correlated more strongly with
summer (June-July) precipitation (r = -0.48). Results from piñon pine sites, however,
correlates most strongly with May-July precipitation (r = −0.43) at the low elevation site,
and cool season temperatures at the mid and high elevation sites. Our results indicate
that 18O records obtained from Douglass-Fir in western Colorado could be a good
proxy of spring temperatures and that 18O from piñon pine may indeed provide climate
information to supplement ring width data. We also assessed whether there was a
difference in isotopic value between earlywood and latewood and found no difference in
isotopic value between the two. Our results also indicate that by using isotopic records
of 18O in conjunction with ring widths it could be possible to develop improved
paleoclimate reconstructions incorporating temperature and precipitation from both the
cool and warm seasons from the same sites. This would provide a valuable tool to
disentangle the climatic influences on snowpack and streamflow in western North
America, in both the past and the present.
~*~
Forgotten Landscapes of California: Using Historical Ecology and Art to
Reconstruct Pre-Contact Ecosystems
Laura Cunningham
Artist-Naturalist (bluerockiguana@hughes.net)
Vernal pools, protected lagoons, grassy hills rich in bunchgrasses and, where the San
Francisco Bay is today, ancient bison and mammoths roaming a vast grassland.
Through the use of historical ecology, Laura Cunningham walks through these forgotten
landscapes to uncover secrets about the past, explore what our future will hold, and
experience the ever-changing landscape of California.
15
Combining the skill of an artist with passion for landscapes and training as a naturalist,
Cunningham has spent more than two decades poring over historical accounts,
paleontology findings, and archaeological data. Traveling with paintbox in hand, she
tracked the remaining vestiges of semipristine landscape like a detective, seeking clues
that reveal the Old California of past centuries. In her studio, Cunningham created
paintings of vast landscapes and wildlife from the raw data she had collected, her own
observations in the wild, and her knowledge of ecological processes. Through A State
of Change, readers can wander through these wondrous and seemingly exotic scenes
of early California and ponder the possibilities for both change and conservation in our
present day landscape.
~*~
The Role of Natural Climatic Trends and Local Depositional Conditions on Peat
Formation in the Sacramento-San Joaquin Delta
Irina Delusinaa and Kenneth L. Verosuba
a The
Earth and Planetary Science Department, UC Davis, CA 95616
(idelusina@ucdavis.edu; klverosub@ucdavis.edu)
The formation of peat in the Delta during the Holocene took place under relatively
constant natural conditions, linked with gradual sea level rise and mild climatic
fluctuations. In general, vegetation persistently resists changes in climate, unless that
change occurs abruptly. However, the wetlands of the Delta are a very sensitive
environment even to minor climatic changes and such changes leave their mark on the
sediment record and subsequent formation of plant communities. For this reason, the
formation of peat in the Delta provides unique insights into climatic processes.
Peat accretion occurred in the Delta under general climatic trends related to climatic
setting and postglacial sea-level change during the last 6500 years. These trends are
reflected in storage of atmospheric carbon in the Delta sediments. In this study of three
peat cores collected from different Delta locations, we use palynological and
paleomagnetic methods to test the hypothesis that there are two influences on peat
deposition: tidal and riverine.
Based on the fact that the bulk density of the peat is closely correlated with organic
carbon content and peat accretion, we found that:
1) There is an inverse relationship between pollen concentration and organic carbon
content. The pollen concentration in the cores is highest prior to intervals with high
carbon content and the warmest intervals, as determined from pollen analysis, precede
period with the highest peat accretion rate;
2) The organic content is inversely related to the lithic content as determined from
paleomagnetic measurements of isothermal remanent magnetization intensity (IRM);
3) A salinity index based on pollen criteria is highest during the highest stands of sea
level and generally corresponds to an increase in Poaceae pollen, which might indicate
the formation of a peat type different from tidal marsh peat.
16
A visible increase in IRM intensity at about 4,000 years B.P. suggests a strong
terrigenous input, which might be related to climatic warming and an increased riverine
contribution to the lithic component of the peat-rich sediments. The coincidence of the
IRM peak with the lowest value of the salinity index support the hypothesis that the
riverine contribution was probably the cause of the increase in the inorganic component
in peat and provided the substrate for the growth of vegetation: this is reflected in the
subsequent increase in total pollen concentration. The pollen concentration though is
inversely correlated with the organic content in the peat. Similar events appear to have
occurred later in the Holocene but on a much shorter time scale.
~*~
3000 years of environmental change at Zaca Lake, California
Theodore Dingemansa, Scott A. Mensinga,*, Sarah J. Feakinsb, Matthew E. Kirbyc,
Susan R. H. Zimmermand
a
Department of Geography, University of Nevada, Reno, NV, USA
(tdingemans@nevada.unr.edu, smensing@unr.edu); b Department of Earth Sciences,
University of Southern California, Los Angeles, CA, USA; c Department of Geological
Sciences, California State University, Fullerton, Fullerton, CA, USA; d Center for
Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore,
CA, USA 8231
We use pollen and sediments to generate a 3000 year record of vegetation and climate
along the southern California coast, with a focus on identifying periods of persistent
drought in the vicinity of Zaca Lake, Santa Barbara County, California. We identify a
multi-centennial scale drought between 2700 and 2000 cal yr BP in Zaca Lake,
corroborating evidence from across the Great Basin and extending the regional spread
of this multi-centennial drought to southern California. Records from the Pacific
Northwest predominantly record wet climate during this same period, similar to the
ENSO dipole pattern. Today the dipole pattern of a dry southwest, wet northwest is
associated with La Niña conditions and there is some evidence from coastal South
America for a weaker El Nino pattern prior to 2000 cal yr BP. In addition, we find
evidence for 3 warm periods between 1350 and 650 cal yr BP which are identified in the
record by the presence of the algae Pediastrum boryanum var. boryanum. The latter
two of these periods, dating from 1070-900 and 700–650 cal yr BP correspond to
droughts during the Medieval Climatic Anomaly identified in other records. A period of
high Salix percentages and high pollen concentration from 500 to 250 cal yr BP
represents the wettest period of the record and coincides with the Little Ice Age.
~*~
17
California droughts associated with La Nina
John A. Dracupa, Robert Willisb.
aDepartment
of Civil & Environmental Engineering, University of California, Berkeley
(dracup@ce.berkeley.edu); b Department of Environmental Resource Engineering,
Humboldt State University, Arcata (rlw@humboldt.edu)
California has experienced 17 droughts since 1827 that have varied in length from two
to eight years. Previous researchers have documented the connection between these
droughts and the cold phase of the Southern Oscillation, known as La Nina. A
summary of these studies has been published as references 1 and 2 below.
This paper, to be presented at the PacLim Conference at Asilomar, CA, March 8-11,
2015, will expand and update previous studies to determine the relationship between
California droughts and La Nina occurrences from 1827 to date. The analysis will
identify the degree of correlation between the severity of the droughts (magnitude as
calculated by duration x magnitude, using rainfall deviation from the mean as the
magnitude) and the severity of the La Nina events, measured using a time series of
Southern Oscillation occurrences.
1. E Kahya, JA Dracup, The influences of type 1 El Nino and La Nina events on
streamflows in the Pacific southwest of the United States, Journal of Climate,
1994.
2. Cole, JT Overpeck and ER Cook, Multiyear La Niña events and persistent
drought in the contiguous United States, Geophysical Research, 2002.
~*~
Insight into Southern California paleohydrology since Marine Isotope Stage 5c (c.
96 ka) from Baldwin Lake, San Bernardino Mountains
Katherine C. Glovera, Glen MacDonalda,b, Edward Rhodesc,d, Emily Silveirae, Matthew
Kirbyf, Alexis Whitakerg
aDept
of Geography, UCLA, Los Angeles, CA 90095 (kcglover@ucla.edu); bDept of
Ecology and Evolutionary Biology, UCLA, Los Angeles, CA 90095; cDept of Earth,
Planetary, and Space Sciences, UCLA, Los Angeles, CA 90095; dcurrent address: Dept
of Geography, The University of Sheffield, S10 2TN United Kingdom
(ed.rhodes@sheffield.ac.uk); eDept of Geological Sciences, CSU-Fullerton, Fullerton,
CA 92831 (emilys226@csu.fullerton.edu); fDept of Geological Sciences, CSU-Fullerton,
Fullerton, CA 92831 (mkirby@exchange.fullerton.edu); gUCLA Institute of the
Environment and Sustainability, 300 La Kretz, Los Angeles, CA 90095
(alexiswhitaker64@yahoo.com)
Baldwin Lake in Big Bear Valley, San Bernardino Mountains (SBM), is a continuous
record that spans the last Glacial and is the basis of a study of southern California’s
long-term paleohydrology. The recovered sediment core is 26.5 m and high-resolution,
filling an important spatiotemporal gap in our knowledge of Western U.S. paleoclimate.
AMS radiocarbon dating and infra-red stimulated luminescence place the core’s age at
18
c. 95.9 – 10 ka. Loss-on-ignition, magnetic susceptibility, and grain size were conducted
throughout the sequence to develop the basin’s formation and hydrologic history.
Baldwin Lake has occupied a closed basin since ca. 95.9 ka. Prior to that, it is
speculated that a westward-draining fluvial environment occupied Big Bear Valley. Once
isolated, the basin accumulated nearly 86 kyrs of sediment in a high relief watershed
that yields high resolution and a record of regional hydrologic variability. Our results
indicate that MIS 5a was wet from 84-79 ka, followed by a period of aridity from 79-72
ka. Hydrologic variability began to fluctuate on a shorter-term millennial scale during
MIS 4, with moisture peaking 66-67 ka. MIS 3 was characterized by a relatively stable
climate with a deep, perennial lake throughout its duration. Declining organic content
and magnetic susceptibility during MIS 2 suggest maximum lake level and the
permanent decline of the lake’s ecologic community. This high stand is approximately
coeval with SBM glaciation and other southern California records that indicate
enhanced moisture availability during the last Glacial.
~*~
A Paleoenvironmental Reconstruction to Assess Anthropogenic and Natural
Disturbances in Range Creek, Utah
Maria Groves
Department of Geography, University of Utah, Salt Lake City, UT 84112
maria.groves@utah.edu
This proposed study will analyze anthropogenic and natural disturbances within the
Range Creek Canyon. An intensive survey of modern vegetation will be used to
calibrate the modern pollen assemblages to current vegetation. A comparative analysis
will investigate the relationship between the spatial distribution of pollen percentages
and the regional climate and vegetation. Pollen surface samples (pinch method) will be
compared with transects data conducted throughout the canyon at five key areas
including riparian zones, open meadows, cliff sides, and areas previously used for
ranching at the turn of the century. The relationship between the modern pollen and the
current vegetation will allow a calibration of pollen to vegetation and pollen to climate
which can then be applied to the fossil-pollen and charcoal in cores taken from Cherry
Meadows and other wetlands. The Cherry Meadows area of the canyon is of particular
importance as it shows evidence of Fremont home and gathering sites. Climatically and
significant species can indicate current and paleoclimate conditions and use by early
peoples. Changes in fire regimes, climate, and human occupation are a vital
component to this significant national archeological site. The sedimentary and
vegetative records will then be compared to geomorphically dynamic areas of the
canyon using X-ray fluorescence (XRF). This new geochemical record may shed light
on the hydrological variability of the canyon and help address changes in the
frequencies and intensities of the North American Monsoon in the southeast region of
Utah. Once this canyon is better understood paleoecological and paleoenvironmental
comparative studies can be carried out in similar local canyons to formulate regional
patterns in an area under analyzed.
~*~
19
Disappearance of coastal forests on Santa Cruz Island, California at the
Pleistocene-Holocene Boundary
Amanda N. Grant
School of Earth Sciences and Environmental Sustainability, Northern Arizona
University, 602 S Humphreys, P.O. Box: 5694, Flagstaff, AZ 86001, ag2486@nau.edu
Not studied since the early 1930’s, plant macrofossils on Santa Cruz Island in the
Channel Islands, California have the potential to show the change in vegetation
communities in response to climatic change at the Pleistocene-Holocene boundary
(~11,500 years ago). On the western side of the island in Cañada de los Sauces
(Willow Canyon) are preserved log and fossil remains deposited in sedimentary layers
that were probably part of alluvium deposited by an ancient stream in the canyon. The
most abundant species of plant remains in the alluvium are those of conifers and
dictyledons, as documented in a preliminary list published by Chaney and Mason
(1934).
Analyzing and identifying these plant macrofossils will open a window to the past,
documenting to show what vegetation communities existed on the Channel Islands
during the Pleistocene at the time of the last glacial maximum. Studying these
macrofossils also has implications for understanding the rainfall, temperature, and soil
type on the islands at this time period. Chaney and Mason found samples of Bishop
pine (Pinus muricata), Douglas-fir (Pseudotsuga menziesii), and Gowen cypress
(Cupressus goveniana) on Santa Cruz Island. These species, aside from Bishop pine,
no longer grow on the island. The closest Douglas-fir stand is found 100 km to the
northwest in Santa Barbara County. Most of these closed-cone species are now found
in northern California and Baja California. Evidence suggests that as climate changed
into the Holocene, vegetation changed on the island to what is now coastal shrublands
and grasslands (Anderson et al., 2008).
Better understanding the vegetation that grew during the Pleistocene, locating a
preserved transition between the Pleistocene and Holocene, and comparing this to the
vegetation seen on the island today will help to clarify the impact current climate change
may have on present day ecosystems. It also will assist in clarifying aspects of the
current controversy surrounding the potential changes associated with a hypothesized
asteroid impact at the transition (Israde-Alcántara et al., 2012; Pigati et al., 2012; Pinter
et al., 2011).
A collecting permit was obtained for the site from the Santa Cruz Island Reserve. I
detailed the complete stratigraphy of five sites in Cañada de los Sauces. In addition, I
have surveyed the canyon to provide the elevations and locations of the macrofossils
with their respect to distances into the canyon and the height above present sea level.
Samples collected consisted primarily of sediments from levels that contained abundant
plant remains, but I also collected wood fragments from the sections.
20
Specimen will be identified in reference to the NAU Herbarium and the Laboratory of
Paleoecology’s plant collection, but wood specimens will be identified at the Forest
Products Laboratory in Madison, WI. Samples will then be radiocarbon dated to
determine their age through Direct AMS at Accium Biosciences. Five samples have
already been dated and the ages range from 15,757 to 17,188 cal BP.
References:
Anderson, R.L., Byrne, R., and Dawson, T. 2008. Stable isotope evidence for a foggy
climate on Santa-Cruz, California at ~16,660 cal. Yr. B.P. Palaeogeography,
Palaeoclimatology, Palaeoecology, 262: 176-181.
Chaney, R.W., Mason, H.L., 1934. Studies of the Pleistocene Palaeobotany of
California. Carnegie Institute of Washington Publications, 415: 1-24.
Israde-Alcaintara, I., Bischoff, J.L., Vazquez, G.D., Li, H.C., DeCarli, P.S., Bunch, T.E.,
Wittke, J.H., Weaver, J.C., Firestone, R.B., West, A., Kennett, J.P., Mercer, C.,
Xie, S., Richman, E.K., Kinzie, C.R., Wolbach, W.S. 2012. Evidence from central
Mexico supporting the Younger Dryas extraterrestrial impact hypothesis. PNAS
Early Edition, 1-5.
Pigati, J.S., Latorre, C., Rech, J.A., Betancourt, J.L., Martinez, K.E., and Budahn, J.R.
2012. Accumulation of impact markers in desert wetlands and implications for
the Younger Dryas impact hypothesis. PNAS- Early Edition, 1-5.
Pinter, N., Scott, A.C., Daulton, T. L., Podoll, A., Koeberl, C. Anderson, S.R., and
Ishman, S.E. 2011. The Younger Dryas impact hypothesis: A requiem. EarthScience Reviews: 106, 247-264.
~*~
El Niño controls Holocene rabbit and hare populations in Baja California
Isaac A. Harta, Jack M. Broughtona, Ruth Gruhnb, Alan Bryanb, c
aDepartment
of Anthropology, University of Utah, 270 South 1400 East room 102, Salt
lake City, UT 84112-0060 (i.hart@anthro.utah.edu); bDepartment of Anthropology,
University of Alberta, 13-15 HM Tory Building, University of Alberta, Edmonton Alberta,
Canada T6G 2H4 (rgruhn@ualberta.ca); cDeceased
The El Niño/Southern Oscillation (ENSO) is a major source of climatic variation
worldwide, with significant impacts on modern human and animal populations. However,
few detailed records exist on the long-term effects of ENSO on prehistoric vertebrate
populations. Here we examine how lagomorph (rabbit and hare) deposition rate,
population age structure and taxonomic composition from Abrigo de los Escorpiones, a
well-dated, trans-Holocene vertebrate fauna from northern Baja California, Mexico, vary
21
as a function of the frequency of wet El Niño events and eastern Pacific SSTs derived
from eastern Pacific geological records. Faunal indices vary significantly in response to
El Niño based precipitation and SST, with substantial moisture-driven variability in the
middle and late Holocene. The late Holocene moisture pulse is coincident with
previously documented changes in the population dynamics of other vertebrates,
including humans. As the frequency and intensity of ENSO is anticipated to vary in the
future, these results have important implications for change in future vertebrate
populations.
~*~
Investigating the Response of a Great Basin Terminal Lake to Abrupt Climate
Change
Benjamin J. Hatchetta and Douglas P. Boylea
aDepartment
of Geography, University of Nevada, Reno, Nevada 89557
benjamin.hatchett@gmail.com
Terminal lakes provide geomorphic, stratigraphic, and sedimentary evidence of past
changes in effective moisture and can be used for reconstructions of regional climate.
However, the lake level chronologies estimated with shoreline deposits and sediment
cores are often weakly constrained within multidecadal timescales (10-100 years). Here
we investigate the surface elevation responses of Walker Lake, a western Great Basin
terminal lake, to abrupt changes in cool season (Oct-Apr) precipitation regimes. An
existing radiocarbon dated lakeshore chronology of Walker Lake suggests that a
complete hydrologic oscillation took place during the Medieval Climate Anomaly (AD
832-1299) with two extended arid periods (243 and 178 year duration) separated by a
47 year pluvial period. Using a semi-distributed water balance model driven by modern
analogs of dry and wet climates, we examined the required magnitude and persistence
of analog climate regimes capable of producing lake level changes consistent with the
lakeshore chronology. Results indicate that modeled lake transgressions could occur
within 10-30 years and regressions could occur within 20-70 years, indicating the likely
role of mechanisms of tropical-midlatitude ocean-atmosphere modes of variability in
driving effective moisture changes in the Great Basin. Our results highlight the utility of
terminal lakes for evaluating global climate model experiments designed to investigate
the physical causes producing both abrupt and extended changes in effective moisture
in dryland regions.
~*~
9,000 years of California weather in an ultra-high resolution scanning XRF record
from Santa Barbara Basin
Ingrid L. Hendya, Tiffany J. Napiera, Erik T. Brownb, Arndt Schimmelmannc, Dorothy
Pakd and Linda Hinnove.
aDepartment
of Earth and Environmental Sciences, University of Michigan, Ann Arbor,
MI 48109 (ihendy@umich.edu). bLarge Lakes Observatory & Department of Earth and
Environmental Sciences , University of Minnesota Duluth, Duluth, MN 55812.
22
cDepartment
of Geological Sciences, Indiana University, 1001 E 10th Street,
Bloomington, IN 47405. dMarine Science Institute, University of California, Santa
Barbara, CA 93106. eDepartment of Atmospheric, Oceanic, and Earth Sciences,
George Mason University, Fairfax, VA 22030.
Extreme weather events in Southern California include both drought and intense rainfall
that are recorded in the elemental composition of Santa Barbara Basin (SBB)
sediments. Warm, dry summers are coupled to the seasonal position of the North
Pacific High pressure system while cool, wet winters are primarily associated with
cyclonic storms originating in low pressure systems in the North Pacific. Extreme
precipitation events in the region occur when strong zonal flow brings warm, moist
tropical air as “atmospheric rivers” across the Pacific. Here we present an ultra highresolution 9,000 year record of the elemental composition of SBB sediments, providing
a Holocene reconstruction of regional riverine clastic input.
The upper 8 meters of jumbo piston core MV0811-14JPC (34°16.906’N; 120° 02.162W,
582 m water depth) were scanned with a second generation ITRAX core scanner at 200
µm intervals for elements including: Al, Br, Ca, Cl, K, Fe, Mn, Rb, S, Si, Sr, Ti and Zr.
This sampling resolution provides between 3 and 7 analyses per year, generating an
annual record. A preliminary age model for the core was generated by stratigraphically
matching planktonic foraminiferal 14C dates from ODP Hole 893A to the new core using
the grey layer sequence identified in both cores. The most recent years of sediment are
missing from the piston core, however overlapping kasten core SPR0901-03KC and box
core SPR0901-04BC scanning XRF records complete the Holocene record.
Flood events identified by grey lithogenic layers are present throughout the Holocene
with a recurrence of ~110 years, but are particularly common (85 year recurrence)
between 4,200 and 2,000 years BP. The longest recurrence interval of ~535 years is
associated with the Medieval Climate Anomaly. Droughts of ~10 to 20 years occur
consistently throughout the Holocene every ~100 to 200 years. An interval between
6,500 and 4,500 years BP that is commonly associated with dry conditions in California
did not contain more frequent or significant droughts, but was associated with fewer
flood events (recurrence interval ~176 years).
~*~
Paleoenvironmental evolution of coastal Northern California - correlative
evidence from the Pacific Ocean and adjacent Coast Range for the past 16 ka
Linda E. Heussera, John A. Barronb, Jason A. Addisonb
aLamont-Doherty
Earth Observatory of Columbia University, Palisades, NY 10601
(heusser@ldeo.columbia.edu); b U.S..Geological Survey, Menlo Park, CA 94025
(jbarron@usgs.gov)(jaddison@usgs.gov)
This paper presents results of a coupled marine-terrestrial study that details the past
16,000 years of coeval terrestrial and marine ecosystem changes in northwestern
coastal California. Pollen in a core taken from Rice Lake on the North Fork of the Eel
River, (40°41' N; 123°30’ W, 1109 m elevation) is compared with pollen analyzed from
23
two marine sediment cores: TN062-O550 taken ~13 km off the mouth of the Eel River
(40°52’ N, 124°34’ W, water depth 550 m) and ODP Site 1019 (41°40.9’ N; 124°
55,8’W, water depth 980 m) taken further north ~ 60 km offshore. The earliest portions
of both the coastal and inland records are dominated by pine (Pinus). Abrupt cooling of
SSTs (sea surface temperatures) at ODP 1019 during the Younger Dryas coincides with
a decrease in pine and an increase in Alnus (alder) and Quercus (oak) at Rice Lake,
indicating dry, unstable conditions. A mosaic of mixed-evergreen forests and oak
woodland at Rice Lake, and redwood (Sequoia sempervirens) rainforests on the coast
develops during the early middle part of the Holocene (~ 9 to 7 ka) coincident with SST
cooling at ODP 1019. An expansion of alder and oak between 4.0 and 3.0 ka in marine
core TN062-O550 suggests a period of increased fluvial transport tied to increased
precipitation. Cool water diatoms and silicoflagellates increase during this same time,
possibly due to a southward migration of the Subarctic North Pacific Front and
concomitant changes in regional atmospheric circulation. The current prominence of
distinctive redwood rainforests on the northernmost California coast began with a rapid,
two-fold expansion of Sequoia at 3.0 ka that coincided with a stepwise increase in
diatom productivity (coastal upwelling). The expansion of Pseudotsuga menziesii
(Douglas fir) at Rice Lake at ~2 ka is likely evidence of the inland penetration of coastal
fog associated with coastal upwelling.
~*~
Spatial Correlation Analysis of ENSO with Southwestern North America
Hydroclimate
Josh P. Heyera, Simon C. Brewera, and Andrea R. Brunelleb
a Department
of Geography, University of Utah, Salt Lake City, UT 84112-9155
(josh.heyer@geog.utah.edu); a Department of Geography, University of Utah, Salt Lake
City, UT 84112-9155 (simon.brewer@geog.utah.edu); b Department of Geography,
University of Utah, Salt Lake City, UT 84112-9155 (andrea.brunelle@geog.utah.edu).
Sea-surface temperature (i.e. SST) variability influences the delivery of winter (i.e.
snow) and summer (i.e. North American Monsoon) precipitation to arid regions of
Southwestern North America. Complicating the delivery of important water resources is
anthropogenic climate change, which is expected to result in warmer and drier
conditions for this drought prone region. Therefore, exploring linkages between largescale climate controls and regional hydroclimate is needed to improve our
understanding of drought, to mitigate potential negative impacts from hydrologic
extremes to human inhabitants and ecosystems. Our analysis investigates spatial
correlations of SST and Southwestern North America hydroclimate during the winter
(December – February) and summer (June – August) seasons. Pearson correlation
maps were created via data provided by the National Center for Environmental
Prediction/National Center for Atmospheric Research (i.e. NCEP/NCAR), the North
American Regional Reanalysis (i.e. NARR), ENSO3.4 and the Pacific Decadal
Oscillation (i.e. PDO) and North Tropical Atlantic (i.e. NTA) sea-surface temperature
indices. Initial results are consistent with prior research, illustrating comparable spatial
correlations of ENSO and hydroclimate using the NCEP data. Results achieved via the
24
NARR data reveal correlations at a higher spatial resolution (i.e. 35km x 35km), not
observable in the NCEP data. These results illustrate one approach to using the NARR
data, and the potential of the NARR data to explore North America hydroclimate at a
higher-spatial resolution.
~*~
10Be
exposure dating of Little Ice Age and Recess Peak moraines in the Sierra
Nevada, California
Alan J. Hidya, Susan R.H. Zimmermana, Robert C. Finkela, Jeorg M. Schaeferb, and
Douglas H. Clarkc
aCenter
for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory,
7000 East Ave. L-397, Livermore, CA, USA (hidy3@llnl.gov); bLamont-Doherty Earth
Observatory, The Earth Institute at Columbia University, Palisades, NY, USA;
cDepartment of Geology, Western Washington University, Bellingham, WA, USA
Constraints on the extent and timing of Holocene glaciations are critical to addressing
standing hypotheses that ascribe climatic fluctuations to changes in atmospheric and
oceanic circulation patterns, or anthropogenic forcing. In the terrestrial record, such
constraints often rely on chronologies obtained from 10Be exposure dating of moraine
deposits. However, the short exposure time of late-Holocene moraines, particularly
those formed during the Little Ice Age (LIA), makes obtaining precise chronologies
extremely challenging. To date, only a handful of LIA deposits (New Zealand, Peru, and
the Swiss Alps) have been successfully dated with 10Be.
Approximately 50 samples obtained from a suite of late-Holocene moraines associated
with the Lyell, Maclure, and Pyramid Peak glaciers in the Sierra Nevada are currently
being analyzed for 10Be (results expected in April 2015). These Sierran results will be
compared to those from New Zealand, Peru, and the Swiss Alps to test the hypothesis
of a globally synchronous LIA deglaciation, which suggests that the LIA was terminated
by anthropogenically-driven warming. Additionally, we will obtain ages from a previously
undated moraine set (below the Maclure Glacier) intermediate between LIA and the
Last Glacial Maximum and correlated to the late-glacial Recess Peak advance.
~*~
High-resolution vegetation and Fire History Reconstruction for the Bonneville
Basin, Utah during the last ~35,000 cal yr BP.
Kelsey A. Howardᵃ, Andrea R. Brunelleᵃ and Jennifer Degraffenriedᵇ
ᵃ Department of Geography, University of Utah, 260 South Central Campus Drive, Rm.
270 Salt Lake City UT, 84112 (kelsey1h@hotmail.com;andrea.brunelle@geog.utah.edu)
; ᵇ U.S. Army Dugway Proving Ground, 5530 Valdez, Dugway UT, 84022
(jennifer.v.degraffenried2.civ@mail.mil)
A paleoecological reconstruction of wetland sediments is being conducted to provide a
high-resolution vegetation, climate and fire history record for Utah’s Bonneville Basin
25
during the late Pleistocene and early Holocene environmental transition of areas near
Callao and Redden Springs, Utah. Both study sites (Redden South Springs, N 39˚ 54’
51.5” W 113˚ 42’ 03.8” and North Redden Springs, N 40˚ 00’ 47.1” W 113˚ 41’ 59.9”) are
located on the western margin of the Great Salt Lake desert and thus provide a nearly
continuous record of the Pleistocene Lake Bonneville and the emergence of prehistoric
and recent human occupation of the basin. Preliminary high resolution charcoal data
from the North Redden Springs sampling suggests the presence of fuel on the
landscape to support increased fire activity during the last ~5000 Cal Yr BP, with a spike
in fire activity at ~1000 Cal Yr BP. After ~5500 Cal Yr BP, a substantial drop in fire
activity occurs to indicate a shift in spring productivity as a result to changes in the
climate system or a change in the fire practices performed by the aboriginal occupants
living within the region. Preliminary analyses of the pollen data indicate a vegetation
composition dominated by xeric shrub communities. Further analyses of the charcoal
and pollen data, as well as data obtained from productivity assessments, high-resolution
erosional analyses and elemental core scanning will allow for a better understanding of
the fluctuating environmental changes occurring in the Bonneville Basin during the last
~35,000 Cal yr BP.
~*~
Assessing Pinus longaeva treeline dynamics using historic aerial imagery
Mackenzie Kilpatricka, and Franco Biondia
of Geography, University of Nevada – Reno, Reno, NV 89506
(mackenziekilpatrick@hotmail.com)
a Department
Increased temperatures caused by climate change can affect plant distributions and
function, especially those that are primarily limited by temperature such as the altitudinal
treeline. Research has found increasing treeline elevations at many treeline sites
throughout the globe, however some treeline sites have not shown altitudinal increases
at all and have remained static or even been depressed. Spatial characteristics of
treelines and the individual trees may influence the response to climate, with spatially
diffuse treelines being the most responsive, while treelines where krummholz treegrowth forms occur have been the least responsive to date. At Mt. Washington in
eastern Nevada, the treeline is primarily composed of bristlecone pine and has both a
diffuse structure and grows as krummholz, making predictions for treeline behavior in
response to continued warming difficult. There is evidence of increased tree-ring growth
in trees on Mt. Washington, however to date no investigations have examined whether
increases in tree density or altitudinal extent have occurred recently. Historic aerial
photos are perhaps the only data source that offers both fine enough spatial resolution
with the needed temporal extent to detect treeline changes in long-lived and biologically
slow paced tree species like bristlecone pine. Here historic aerial photographs from
1945 and 2013 NAIP imagery were examined using object-based image analysis and
manual image interpretation to assess changes in tree density and spatial extent.
Preliminary results show increases in canopy cover and increased stand density have
occurred while altitudinal increases have been minimal. Future work will entail the high
precision geo-referencing and field data collection for individual tree stems to further
refine the classifications by incorporating tree size into the classifications. It is hoped the
26
field measurements will provide a precise baseline dataset for monitoring treeline
changes at this site and other treeline bristlecone pine stands.
~*~
Evidence for abrupt changes in late-Glacial to Holocene hydroclimates in the
Mojave Desert, CA.
Matthew E. Kirbya*, Edward J. Knellb, William T. Andersonc, Matthew S. Lachnietd, Holly
Eega, Ricardo Luceroa, Rosa Murrietaa, Andrea Arevaloa, Emily Silveiraa, Christine
Hinera, and Jennifer Palermoa
aCalifornia
State University, Fullerton, Department of Geological Sciences, Fullerton, CA
92834 USA (*mkirby@fullerton.edu); bCalifornia State University, Fullerton, Department
of Anthropology, Fullerton, CA 92834 USA; cFlorida International University,
Department of Earth and Environment, Miami FL 33181, USA; dUniversity of Nevada
Las Vegas, Las Vegas, NV 89154, USA
Silver Lake is the modern terminal playa of the Mojave River. As a result, it is well
located to record both influences from the winter precipitation dominated San
Bernardino Mountains – the source of the Mojave River – as well as the late-summer to
early-fall North American monsoon. Here, we present various physical and geochemical
data from a new 8.2 m sediment core taken from Silver Lake, CA that spans modern
through 14.8 kcal yrs BP. Age control is based on six bulk organic C radiocarbon dates
and one bulk >125 m ostracod radiocarbon date processed with Bacon v2.2 to
generate an age model. Texturally, the core varies between a sandy clay, a clayey
sand, and a sand-silt-clay, often with abrupt sedimentological transitions. Our working
hypothesis states that high percent clay values indicate persistent standing water
wherein the deposition, accumulation, and preservation of fine grain sediment exceeds
some undefined thickness that inhibits deflation during succeeding desiccation events
or ephemeral lake environments. Based on this clay – lake status hypothesis, the
sediment core is divided into five lake status intervals using percent clay for timing. Clay
values are highest between 14.4 – 13.6 kcal yrs BP, coeval to Lake Mojave II. Clay
values decrease abruptly at 13.6 kcal yrs BP (encapsulating the Younger Dryas)
indicating a return to an ephemeral lake. At 11.6 kcal yrs BP, clay values rise abruptly
indicating a return to a perennial lake; this early Holocene pluvial ended abruptly at 7.4
kcal yrs BP. From 7.4 – 4.2 kcal yrs BP, clay is low, but variable and mud cracks are
common. This mid-Holocene interval is also characterized by sand dominant in the 250
– 500 µm size fraction, the same size fraction most common in the nearby Kelso Dunes.
From this, we interpret the period between 7.4 – 4.2 kcal yrs BP as the interval of peak
Holocene aridity with enhanced dune activity. At 4.2 kcal yrs BP, clay values increase
but only moderately indicating a return to more frequent but short-lived, perennial lakes.
An analysis of forcings implicates changing winter – summer insolation, tropical and
northern Pacific sea surface temperatures, and the El Nino – Southern Oscillation as
the primary drivers of Holocene climate. A comparison to winter dominated Leviathan
Cave (NV) (Lachniet et al., 2014) and the monsoon dominated Pink Panther Cave (NM)
(Asmerom et al., 2007) is used to examine the relative influences of winter vs. summer
precipitation over the Holocene.
~*~
27
Potential non-climate forest structure change in the southern Sierra Nevada
range using paleoenvironmental and archaeological proxy data
Anna Klimaszewski-Pattersona, Scott Mensinga, Linn Gassawayb
a
Department of Geography, University of Nevada, Reno, NV 89557
(annap@nevada.unr.edu); b U.S. Forest Service, Sequoia National Forest, Hume Lake
Ranger District, Dunlap, CA 93621 (gassaway@fs.fed.us)
Interpretation of paleoenvironmental proxy records is essential in understanding
landscape-level change in response to climatic and/or anthropogenic forces. While
stand-alone inferences can be made from a single proxy type, difficulty often arises in
attempting to synthesize proxy data from different temporal scales (annual vs.
centennial) for more robust interpretations of change. Such synthesis is necessary in
teasing out climatic vs anthropogenic causes for paleolandscape change. In this paper,
we explore comparisons of annual dendroclimatically-derived data with sub-centennial
sedimentary pollen and charcoal records from Sequoia National Forest, California, in
relation to Native American burning practices. We hypothesize that during cool, wet
periods that favor closed-canopy species, Native American fire use preserved opencanopy taxa, producing proxy signals contrary to those expected by climate. We expect
forest composition was climatically influenced during the Medieval Climate Anomaly,
coinciding with decreased native populations in the Sierra Nevada. We aggregated local
dendroclimatic records (independent climate proxy) to the temporal scales of pollen and
charcoal data for direct comparison between these proxy records for the last 2000
years. We find support for our hypotheses in comparison of these records. Opencanopy taxa are retained at higher levels unexpected by climate during cool, wet
periods coinciding with increased Native American populations. We also find that forest
structure appears climatically-influenced during warm, dry periods, or periods of
reduced native populations. We propose that Native American use of fire can be evident
in the paleoenvironmental record, and that such records should be interpreted both with
climatic and anthropogenic factors in mind.
~*~
Evaluating the Cause of Deglacial-Age Highstands in the Great Basin Using
Clumped Isotope Thermometry from Shell and Sedimentary Carbonates in
Shoreline Deposits in the Southeastern Basin and Range
Andrew L. Kowlera and Aradhna Tripatia
a
Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, CA 90095
(kowler@email.arizona.edu)
The last glacial-interglacial transition was marked by major perturbations to the global
climate system. Interactions between the ocean and cryosphere in the northern Atlantic
region led to abrupt discharges of freshwater during Heinrich events and meltwater
pulses, disrupting the Meridional Overturning Circulation and thus causing major
perturbations of the climate system and regional hydrologic cycles worldwide.
Radiometric dating of pluvial highstand shorelines in the western U.S. reveal that the
28
majority were formed during the Heinrich 1 stadial (H1: ~18-14.5 ka), when the Great
Basin reached its late Pleistocene hydrologic maximum. In response to this
observation, workers have invoked different mechanisms to explain such rapid transport
of moisture into interior western North America, including enhanced winter storm
tracking due to a southward shift of the Polar Jet Stream, or enhanced summer
monsoons carrying moisture northward from the Gulf of California. However, the
plausibility of either hypothesis hinges on the timing of highstands in the southern Basin
and Range (SBAR), where few paleoshorelines have been dated. The modern North
American monsoon, confined to the SBAR, depends upon the creation of a thermal
trough from sensible heating of the Mexican Plateau, whereas the “monsoon”
hypothesis invokes large-scale atmospheric phenomena to explain the extension of
monsoon circulation into the northern Great Basin (~42oN). Paleobotanical evidence
from late Pleistocene packrat middens in the SBAR shows that C4 grasslands extended
as far north as 35oN, reflecting a similar-to-modern footprint of the paleomonsoon and
suggesting that Great Basin highstands were caused by increased winter precipitation.
Ultimately, evaluating the plausibility of the monsoon hypothesis will require knowledge
of the timing and summer temperatures associated with highstands throughout western
North America. Toward this end, we present the first clumped isotope
paleotemperature estimates from the SBAR, from carbonates and gastropod shells in
radiocarbon-dated shoreline deposits in Willcox basin, southeastern Arizona.
~*~
Environmental magnetism record from Clear Lake, California
Emily Levina, Roger Byrneb, Cindy Looyc, David Wahld, Anders Norene, and
Kenneth L. Verosuba
a Dept.
of Earth and Planetary Sciences, University of California at Davis, Davis, CA
95616 (mlevin@ucdavis.edu) (klverosub@ucdavis.edu); b Geography Department,
University of California at Berkeley, Berkeley, CA 94720 (arbyrne@berkeley.edu); c
Department of Integrative Biology and Museum of Paleontology, University of California
at Berkeley, Berkeley, CA 94720 (looy@berkeley.edu); d United States Geological
Survey, Menlo Park, CA 94025 (dwahl@usgs.gov); e University of Minnesota-Twin
Cities, Minneapolis, MN 54455 (noren021@umn.edu)
We are studying the magnetic properties of a 150-m drill core from Clear Lake in
northern California in order to understand how paleoclimatic and other
paleoenvironmental processes are reflected in its sediments. Our measurements
encompass natural remanent magnetization (NRM), anhysteretic remanent
magnetization (ARM) and saturation isothermal remanent magnetization (SIRM) using
stepwise, alternating field demagnetization. Secondary components of NRM are
removed by the 20 mT demagnetization step, allowing us to obtain a record of the
variations in the direction of Earth’s magnetic field through time. Long-term trends in
ARM intensity indicate that four paleoenvironmental regimes are reflected in the core.
The top 18 meters represent a low intensity zone with a very short high intensity zone at
the very top of the core. From 18-32 meters depth, there is a transition from lower
intensities to higher intensities. The high intensity interval extends from 32 to 90 meters
29
depth. From 90 to 150 meters (base of the core), ARM intensity oscillates between very
high and low values. These results demonstrate that the concentration of magnetic
material supplied to the lake basin varied with time, implying changes in the
paleoenvironmental conditions. Normalized ARM intensity values show that the high
(low) concentration intervals correspond to intervals of slightly higher (lower) magnetic
coercivity. The directional record obtained from NRM measurements shows possible
excursions in geomagnetic direction during some intervals of low NRM intensity. These
may correlate with known geomagnetic excursions and, if so, would provide useful
chronostratigraphic marker horizons for the environmental magnetic record of Clear
Lake.
~*~
Late-Holocene Changes in Climate Variability, Variance, and Periodicity in the US
Southwest, and Effects on Landscape Dynamics
Julie Loisela,b and Glen M. MacDonalda,b,c
aInstitute
of the Environment and Sustainability, UCLA, Los Angeles CA 90095
(juloisel@hotmail.com, macdonal@geog.ucla.edu); bDepartment of Geography, UCLA,
Los Angeles CA 90095; cDepartment of Ecology and Evolutionary Biology, UCLA, Los
Angeles CA 90095
Tree ring-derived Palmer Drought Severity Index (PDSI) time series have been widely
used in the United States to estimate the spatial extent, temporal depth, timing, and
intensity of late-Holocene droughts. However, regional changes in drought variability,
variance, and periodicity have only received little attention. Exploring how the climate
has varied through time using these indices is particularly important and relevant for arid
and semi-arid regions, which are prone to high hydroclimatic variability which, in turn,
impacts landscape ecogeomorphology and associated processes such as vegetation
dynamics, fire recurrence, and sediment transport.
Here we use spectral analysis and autoregressive conditional heteroscedasticity models
to assess changes in periodicity as well as the ‘volatility’ and change in variance of
PDSI time series, respectively. Preliminary spectral analysis using 400-year time
windows indicates statistically significant (> 99% confidence interval) 5-to-7-year
periods throughout most of the record that could be a manifestation of the El NiñoSouthern Oscillation (ENSO). Interestingly, these 5-to-7-year cycles were absent during
the Medieval Climate Anomaly (MCA), a time period known to be drier than average.
The MCA was also characterized by reduced PDSI variability. When combined with
records of prolonged droughts, this reduced variability provides support for a La Niñalike MCA climate regime. Conversely, the Little Ice Age (LIA) was characterized by
higher-than-average climate variability, in line with recurrent El Niño years. Regional
patterns of climate variability, variance, and periodicity are being analyzed and will be
compared to paleoecological and geomorphological records of late-Holocene landscape
evolution.
~*~
30
A Fire History of Upper Valley near Escalante, Utah
Kate Magargal
Department of Anthropology, University of Utah, Salt Lake City, UT 84112
Knowledge of the dynamics of past fire behavior plays a key role in numerous
contemporary research and land management efforts. Teasing apart the relationship
between ecological trends, climate events and anthropogenic effects on past and
present fire regimes requires high spatial resolution of paleoecological proxies. One
area deserving greater attention and paleoecological research is the desert uplands of
central Utah. The high amount of variability in topography and ecotones in this region
make it an ideal candidate for examining variations in past fire regimes. I present
preliminary results of charcoal counts from a well-stratified dry-sediment record in Upper
Valley near Escalante, Utah. Once complete, this project will provide a fire history based
on charcoal, pollen counts, and an age-depth model.
~*~
Search for uncertain relationships between North Pacific atmosphere variability
and western US streamflow drought
Steven B. Malevicha and Connie Woodhouseb
a
Department of Geosciences and Laboratory of Tree-Ring Research, The University of
Arizona, Tucson, AZ 85721 (malevich@email.arizona.edu); b School of Geography and
Development and Laboratory of Tree-Ring Research, The University of Arizona, Tucson
AZ 85721 (conniew1@email.arizona.edu)
This work explores a unique approach to defining wintertime PNA-like dynamics,
between the Aleutian low and atmosphere ridges, as they relate western US streamflow
variability. Wintertime storms transport moisture from the Pacific ocean and are a
primary source for western US streamflow. Studies through the past several decades
have recognized that the western US hydroclimate is influenced by the intensity and
phasing of ocean and atmosphere dynamics and teleconnections, such as ENSO and
North Pacific variability. This complex influence is realized in atmospheric circulation
along the west coast of North America. Regional, synoptic-scale atmospheric circulation
can encourage preferential flow in winter storm tracks from the Pacific, influencing
where moisture will be made available to river basins. These relationships have been
measured with traditional atmospheric indices based on values from fixed points in
space or principal component loadings. This study uses collective search agents to find
and quantify the position and intensity of targeted atmosphere features in climate
reanalysis datasets. Preliminary results highlight the spatio-temporal relationship
between semi-permanent atmosphere characteristics and naturalized streamflow from
major river basins of the western US. Probabilistic graphical models are used to quantify
the relationship between patterns in the atmosphere and streamflow while accounting
for uncertainty from climate processes and data availability. This approach ultimately
creates probabilities densities for semi-permanent atmosphere features which can be
associated with droughts, based on spatiotemporal atmosphere-streamflow relations
observed in the instrumental record.
~*~
31
BirdReturns: Demonstrating Dynamic Conservation
Sandi Matsumoto
The Nature Conservancy (smatsumoto@tnc.org)
In California, water is frequently the limiting factor to creating sufficient habitat for a
range of species, including migratory birds. Dynamic conservation, which uses precision
science to identify what water is needed, when and where, as well as a delivery
mechanism such as a reverse auction, is a promising solution to provide reliable water
to support plants and animals in the context a thriving Californian population and
economy.
In nine short months, the Conservancy brought the novel idea to achieve dynamic
conservation from concept to implementation. Through an innovative program,
BirdReturns, the Conservancy used cutting edge science to inform one of the first-ever
reverse auctions for habitat. The result was ~11,000 acres of high quality habitat that
benefited hundreds of thousands of shorebirds, ducks and geese. Even more
importantly, the pilot proved that temporary, dynamic habitat can be created as a
complement to traditional conservation tools, such as permanent protection and habitat
restoration. While permanent solutions are usually preferable, temporary, dynamic
habitat can be less expensive than permanent habitat, even if the temporary habitat is
acquired annually over the course of hundreds of years.
Taken together, acquisition of permanent and temporary habitat can be combined to
achieve habitat on the scale necessary to sustain the heart of the Pacific Flyway’s
wintering grounds.
~*~
Geochronology and Lithostratigraphy of the Late Pleistocene Las Vegas
Formation
Craig R. Manker a, b, Kathleen Springera, b, Jeffrey S. Pigatib, Shannon Mahanb
aSan
Bernardino County Museum, Redlands, CA 92374; bU.S. Geological Survey,
Denver Federal Center, Denver, CO 80225
The upper Las Vegas Wash preserves some of the most extensive paleowetland
deposits in the American Southwest. Investigations since 2003 by the San Bernardino
County Museum (SBCM) in collaboration with the USGS, have focused on establishing
the geologic and temporal context of hundreds of late Pleistocene vertebrate fossils in
~11,000 acres of the wash. Fine-grained groundwater discharge deposits of the upper
Las Vegas Wash are known informally as the Las Vegas Formation. The Las Vegas
Formation is comprised of stratigraphically ascending units A through G and intervening
soils, with units F, E and B containing respective subunits. Targeted chronometric
dating techniques were employed to augment the initial studies from the 1960’s, and to
address outstanding ambiguities regarding the disposition, age, and duration of these
stratigraphic units. Although successive investigators have made significant
contributions in establishing age ranges and lithologic descriptions for these units, many
32
long-standing questions have persisted due to the complexity and incomplete spatial
preservation of the deposits. In this study, we addressed questions regarding the
unknown age of unit B2, the stratigraphic and temporal disposition of unit C, and the
lithologic variability and ages of units D and E1 – specifically, whether lithologic
variability in these units is the result of contemporaneous facies changes, or that the
variable lithologies represent discrete discharge episodes. Field observations
demonstrate that units associated with spring discharge are separated by stable surface
periods and/or erosion events indicating the initiation and abrupt cessation of discharge
during key periods within the stratigraphic record. Here, we present results on the
construction of a new temporal framework and a revised detailed lithostratigraphy for
the Las Vegas Formation derived from radiocarbon and luminescence dating
techniques. Our investigation reveals a complex depositional system dominated by
episodic groundwater discharge punctuated by relatively brief hiatuses. Temporal
bracketing of the discharge hiatuses allowed for the development of high-resolution
wet/dry sequences, which closely track northern hemispheric cold/warm oscillations in
the Greenland ice core records.
~*~
The role of the PDO in western U.S. drought
Stephanie A. McAfee
Department of Geography, University of Nevada, Reno, Reno, NV 89557
(smcafee@unr.edu)
Researchers from many fields are hotly debating the cause or causes of the drought
currently plaguing California and Nevada. Of particular concern is whether the drought
is driven by internal variability of the climate system or whether it can only be explained
by societal influence on the climate system. One potential (and popular) culprit is the
Pacific Decadal Oscillation or PDO, a pattern of variability in northern Pacific sea
surface temperatures. Variability in the PDO has also been proposed as a mechanism
for significant droughts recorded in the paleoclimate record. Yet disagreements between
reconstructions of the PDO have made linking past droughts with the PDO challenging.
Reinvestigation of the PDO’s influence on temperature and precipitation over the
western United States during the observational period suggests that disagreements in
these reconstructions stem from variability in the influence of the PDO on temperature
and precipitation in western North America. Such temporal instabilities in
teleconnections make it challenging to link droughts, whether current or historical, to
ocean variability through statistical methods alone. These results also suggest that the
PDO may not be particularly useful as seasonal forecast tool, and using it is as a way of
understanding past climate is especially problematic.
~*~
33
Arctic and Tropical Influence on Extreme Precipitation Events, Atmospheric
Rivers, and Associated Isotopic Values in the Western U.S.
Staryl E. McCabe-Glynna, Kathleen R. Johnsona, Yuhao Zoua, Jeffrey M. Welkerb,
Courtenay Strongc, Jonathan J. Rutzd, Jin-Yi Yua, Kei Yoshimurae, Scott L. Sellarsa and
Ashley E. Paynea,
aDepartment
of Earth System Science, University of California Irvine, Irvine, CA,
mccabegs@uci.edu, kathleen.johnson@uci.edu, yzou@uci.edu, jyyu@uci.edu,
scott.sellars@uci.edu, aepayne@uci.edu; bDepartment of Biological Sciences,University
of Alaska Anchorage, Anchorage, AK, jmwelker@uaa.alaska.edu; cDepartment of
Atmospheric Sciences, University of Utah, Salt Lake City, UT, dNOAA, Boulder, CO,
United States, jonathan.rutz@noaa.gov, eAtmosphere and Ocean Research Institute
University of Tokyo, Tokyo, Japan, keiyoshi08@gmail.com
Extreme precipitation events along the U.S. West Coast can result in major damage and
are projected by most climate models to increase in frequency and severity. One of the
most prevalent extreme precipitation events that occurs along the west coast of North
America are known as 'Atmospheric Rivers' (ARs), whereby extensive fluxes of water
vapor are transported from the tropics and/or subtropics, delivering substantial
precipitation and contributing to flooding when they encounter mountains. This region is
particularly vulnerable to ARs, with 30-50% of annual precipitation in this region
occurring from just a few AR events. Because of the tropical and/or subtropical origin of
ARs, they can carry unique isotopic properties. Here we present the results of analysis
of weekly precipitation data and accompanying isotopic values from Giant Forest, in
Sequoia National Park, in the southwestern Sierra Nevada Mountains (36.57° N;
118.78° W; 1921m) from 2001 to 2011. To better characterize these events, we focused
on the 10 weeks with the highest precipitation totals (all greater than 150 mm) during
the study period. We show that nine of the top ten weeks contain documented 'AR'
events and that 90% occurred during the negative phase of the Arctic Oscillation. A
comparison of extreme precipitation events across the Western U.S. with several key
climate indices demonstrate these events occur most frequently when the negative
phase of the Arctic Oscillation is in sync with the negative phase of the El Niño Southern
Oscillation (ENSO) and the negative or neutral Pacific North American (PNA) pattern.
We also demonstrate that central or eastern Pacific location of ENSO sea surface
temperature anomalies can further enhance predictive capabilities of the landfall
location of extreme precipitation. Stable isotope results show that extreme precipitation
events are characterized by highly variable δ18O (-7.20‰ to -19.27‰), however, we find
that more negative δ18O values typically occur during the negative PNA pattern. Finally,
we will present the results of data comparison with NCAR-NCEP reanalysis, Hysplit
back trajectories, and isotope enabled climate model (IsoGSM) results.
~*~
34
What has driven the long-term drying of the Southwest: precipitation or
evaporation? A paleohydrologic study at multiple lake basins in California
John Meringa, Juan Loraa, Aiden Jonssona,b, Victoria Petryshyna, John Wilsona, Audrey
Browna, Lilian Choua, Angela Jaykoc, David Millerc, Kate Maherd, Daniel Ibarrad, Robert
Eaglea, Camille Risie, Andrew Kowlera, Jonathan Mitchella, Aradhna Tripatia,b
a
Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, CA 90095
(johnmering@gmail.com); b Atmospheric and Oceanic Sciences, UCLA, Los Angeles,
CA 90095; c United States Geological Survey, Menlo Park, CA 94025; d School of Earth
Sciences, Stanford University, Stanford, CA 94305; e Laboratoire de Météorologie
Dynamique, Paris, France
Anthropogenic warming is expected to intensify droughts across the Southwestern
United States. In California this is problematic, where water resources are already
overdrawn. Data on past variability in temperature and moisture can be used to study
regional climate sensitivity and assess water budget calculations. Specifically, lacustrine
deposits are physically and chemically sensitive to changes in the balance between
precipitation and evaporation. Here, we evaluate past hydrographic conditions in five
regions: Mono Lake, Owens Lake, Surprise Valley, the Los Angeles Basin, and the
Mojave, using carbonate clumped isotope thermometry and oxygen isotopes. These
lake systems achieved highstands during, and in some cases after, the Last Glacial
Maximum (LGM), but began to retreat before 12 ka BP. Clumped isotope analyses were
carried out on multiple phases of ancient lacustrine material, including endogenic
calcite, and aragonitic mollusk shells. We reconstruct lake surface temperature, air
temperature, and the oxygen isotope composition of paleolake water. We compare our
results to outputs from PMIP3 and CMIP5 climate models, as well as high-resolution
oxygen isotope-enabled climate models for precipitation. Ultimately, we provide
guidelines for integrating stable isotope based proxies with climate models, and propose
interpretations of the long-term drying out of the Southwest.
~*~
Recruitment patterns and growth of high-elevation pines in response to climatic
variability (1883-2013), western Great Basin, USA
Constance.I. Millara, Robert.D. Westfalla, Diane.L. Delanya, Alan.L. Flintb, and Lorrie.E.
Flintb
a USDA
Forest Service, Pacific Southwest Research Station, 800 Buchanan St., Albany,
CA 94710; Emails: cmillar@fs.fed.us, bwestfall@fs.fed.us, ddelany@fs.fed.us;
b US Geological Survey, California Water Science Center, 6000 J St., Sacramento, CA
95819, Emails: aflint@usgs.gov; lflint@usgs.gov
Over the period 1883—2013, recruitment of subalpine limber pine (Pinus flexilis) and
Great Basin bristlecone pine (P. longaeva) above upper treeline, below lower treeline,
and across middle-elevation forest borders occurred at localized sites in the western
Great Basin. A synchronous pulse at all ecotones occurred between 1963—2000
(limber pine) and 1955—1978 (bristlecone pine), when pines expanded 225 m beyond
35
forest borders. Little recruitment occurred before this interval or in the 21st century. No
obvious environmental factors distinguished recruitment from non-recruitment locations.
Where their ranges overlap, limber pine has leap-frogged above bristlecone pine by 300
m. Limber pine tree-ring chronologies, developed to compare radial-growth responses
to recruitment, showed dominant pulses of increased growth during the same interval as
recruitment at all but a low elevation site. Significant climate correlations of growth and
recruitment indicated lead and lag effects as much as six years, and complex
relationships with climate variables, corroborating the importance of cumulative climate
effects relative to any single year. Water relations were the most important drivers of
growth and recruitment, and interacted with growing-season minimum and maximum
temperatures. These results underscore the importance of studying ecotones at all
margins when evaluating conifer response to climate change.
~*~
Resilience of American Southwest Ecosystems to Prolonged Drought
Thomas A. Minckley
Department of Geography, University of Wyoming, Laramie, WY 82071
(minckley@uwyo.edu)
Over the past decade, sedimentary analyses of desert wetland and spring sediments
from western North America have identified periods of millennial scale droughts.
Further, this work has revealed the resilience of desert regions to not only respond to
drought, but rapidly rebound as water availability increases. Records from desert
wetlands show good pollen preservation during pluvial periods, but a near absence of
pollen data during prolonged drought. Isotopic analyses indicate that wetland surfaces
shift to grasslands during identified droughts. Finally, changes in hydrological flow
through wetlands can be inferred by trends in carbonates found in desert wetland
sediments. These interpretations are based on Loss-on-Ignition analysis, which for
carbonates are inferred to represent resident time of water flowing through the system.
While many questions remain on the geologic controls and permanence of desert
wetlands in western North America, their potential to provide unique information about
the large basins of the region is largely untapped.
~*~
Two shades of grey: Understanding temperature-streamflow relationships in the
Colorado River Basin through the lens of gridded climate data
Kiyomi Morinoa and Connie Woodhousea,b
a
Laboratory of tree-Ring Research, The University of Arizona, Tucson, AZ, 85721
(kmorino@ltrr.arizona.edu); b School of Geography and Development, The University of
Arizona, Tucson, AZ, 85721.
In light of current and projected warming trends, a more local understanding of how
temperature impacts streamflow is becoming increasingly important for water resource
36
managers. Indeed, this is particularly critical in the West, where complex mountainous
topography characterizes many of the major runoff generating regions. For these
investigations, gridded climate data can be particularly useful due to its uniform
coverage of areas of interest. In this study, we look at how temperature might be
influencing streamflow on the Colorado River by characterizing spatial and temporal
patterns of association between temperature and streamflow in the upper portion of the
Colorado River Basin. We focus on the Upper Basin as it is the source of over 80% of
flow in the Colorado River. We examine the association of both maximum and
minimum temperature to streamflow, after taking precipitation into account. Because
gridded climate data may be biased if source data are not fully screened for
inhomogeneities, and/or due to changes in numbers of stations over time, we conduct
this analysis on two gridded data sets, PRISM and the recently developed TopoWx. In
the latter, climate input data was homogenized whereas in the former, input data was
not. These data sets, however, additionally differ in other aspects, including spatial
resolution and interpolating algorithm. In this analysis, we assume that any major
differences in spatial and temporal patterns of temperature associations with streamflow
arise primarily due to issues of source data homogeneity. We discuss the implications
of these potential differences for understanding the role of temperature in streamflow
variability.
~*~
Reconstructing Pleistocene precipitation events from Santa Barbara Basin
sediment cores: application of the detrital elemental proxy at annual resolution
Tiffany J. Napiera, Ingrid L. Hendya, Erik T. Brownb, and Linda Hinnovc
a Department
of Earth and Environmental Sciences, University of Michigan, Ann Arbor,
MI 48109 (tinapier@umich.edu) b Large Lakes Observatory and Department of Earth
and Environmental Sciences, University of Minnesota Duluth, Duluth, MN 55812
c Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University,
Fairfax, VA 22030
Mean annual precipitation is predicted to decrease in California in the future, although
heavy precipitation events may become more frequent. Rainfall patterns in Southern
California directly affect availability of water resources, and extreme weather
exacerbates water stress and societal impacts in this highly populated and agriculturally
important region. In order to reconstruct annual precipitation history, both the magnitude
and recurrence intervals, in southern California, we have analyzed sediment from five
Pleistocene (~400-450 ka [MIS 11 and 12] and ~735 ka [MIS 18]) cores collected in
Santa Barbara Basin using data from XRF core scans and ICP-MS and -AES analyses
for elements associated with the terrigenous siliciclastic detrital fraction of core
sediment (Al, Fe, Rb, Si, Ti). We date the cores with an annual floating age model
developed using a bandpass filter to isolate the annual signal in the siliciclastic detrital
fraction. Siliciclastic detrital element concentrations increase in samples associated with
precipitation events and floods, and decrease in samples associated with droughts.
Variability of these elements can thus be used as a proxy for precipitation and river
runoff. We investigate changes in annual detrital sediment input during extremes in
glacial/interglacial climate states and due to rapid climate change (centennial to
37
millennial time scales). These results provide basic information on the nature and
response of precipitation patterns due to past changes in climate forcing. This will
improve climate predictions for this region, especially interannual and decadal variability
that impact climate on human timescales (i.e. <100 years).
~*~
Late Holocene (3.65 ka) multi-proxy shift in Fallen Leaf Lake, CA marks the
transition from a millennial-scale neopluvial interval to increased aridity
Paula J. Noblea, Susan H. Zimmermanb, G. Ian Ballc, Ken D. Adamsd, Jillian Maloneye,
and Shane B. Smithf
aDepartment
of Geological Sciences and Engineering, University of Nevada, Reno, NV
89557 (noblepj@unr.edu); b Center for Accelerator Mass Spectrometry, Lawrence
Livermore National Laboratory, Livermore, CA 94550 (zimmerman17@llnl.gov);
cScripps Institute of Oceanography, Geosciences Research Division, La Jolla, CA
92093, (ianball@gmail.com); dDesert Research Institute, 2215 Raggio Parkway, Reno,
NV 89512 (Ken.Adams@dri.edu); eDepartment of Geological Sciences, San Diego
State University, San Diego, CA 92182 (jillian.maloney@gmail.com); fFUGRO
Geoconsulting, 6100 Hillcroft Ave., Houston, TX, 77081 (shanebsmith@gmail.com)
A mid Holocene dry period has been reported from lake records in the Great Basin and
Sierra Nevada, yet the spatial and temporal extent of this interval is not well understood.
We present evidence for a millennial-scale interval of high winter precipitation
(neopluvial) at the end of the mid Holocene in the Lake Tahoe-Pyramid Lake watershed,
that reached its peak around 3.7 kcal yr BP. In cores from Fallen Leaf Lake (FLL) in the
Tahoe basin, the end of the neopluvial is dated at 3.65  0.09 kcal yr BP and is the
largest post-glacial signal in the cores. The neopluvial interval is interpreted to be a
period of increased snowpack in the upper watershed, supported by depleted δ 13Corg (27.5‰), negative baseline shifts in TOC and TN, lower C:N, and high abundances of
Aulacoseira subarctica, a winter-early spring diatom. Collectively, these proxies indicate
cooler temperatures, enhanced mixing, and/or shortened summer stratification resulting
in increased algal productivity. The neopluvial interval ends abruptly at 3.65 ka, with a
change from mottled darker opaline clay to a homogeneous olive clay with lower BSi
content, decreased A. subarctica and opal, and followed by a 50% reduction in
accumulation rates. The δ13Corg becomes enriched by 2‰ and TOC, TN, and C:N all
show the start of positive trends that continue through the remainder of the Holocene. At
Pyramid Lake, existing ages on shorelines indicate a significant lake-level rise
beginning at some point after 5 kcal yr BP and reaching a highstand of about 1186 m
between 3.8 – 4.1 kcal yr BP (Briggs et al., 2005), but new OSL ages on Holocene
shorelines are pending. In the Walker, Mono, and Owens lake basins, the neopluvial
shorelines represent the highest late Holocene shorelines (Stine, 1990; Adams et al.,
2014). Collectively, these studies indicate that the neopluvial and subsequent
aridification intervals were at least regional in scale.
~*~
38
Latest Pleistocene through Holocene Lake Levels from Tulare Lake, CA: Testing
results using the Smear Slide Technique
Kelsey Padillaa, Lindsey Medinaa, Ashleigh Blunta, and Rob Negrinia
a Department
of Geological Sciences, California State University, Bakersfield, 9001
Stockdale Hwy., Bakersfield, CA 93311 (kelpad91@aol.com)
The core-based, lake-level proxy record of Blunt (2013) for Tulare Lake, CA has
extended the trench-based record of Negrini et al. (2006) back to ~20,000 years ago for
Tulare Lake. Furthermore, the former has an improved resolution corresponding to one
sample every ~50 years, making it more useful towards decadal-scale forecasts of
recharge. This study uses the smear slide technique of Schnurrenberger et al. (2003) to
test the findings of Blunt (2013). The technique involves smearing chemically and
physically unaltered sample onto a glass microscope slide using Norland optical cement
as a medium and curing with an ultraviolet light.
The smear slide technique allows for a detailed petrographic microscopic description of
the unconsolidated core sediments for every 5cm, including the detection of features
diagnostic of both deep, freshwater and shallow, brackish water paleoenvironments.
The geobiological and granular results are generally consistent with the predictions of
Blunt (2013). For example, the concentration of phytoliths, specifically grass tracers, are
consistent throughout the core with high levels of previously documented carbon to
nitrogen (C/N) ratios and an organic molecule ratios index for grasses from leaf waxes.
At the lower end of the record, the interval hypothesized to contain sand-sized grains of
Tioagan-aged glacial outwash from the Sierra Nevada ice cap, have, as predicted, little
to no organic matter or carbonate present and are characterized by sand grains of
granitic composition. In the time interval from 2,500 to 1,800 cal. yr. BP, Blunt (2013)
suggests shallow, freshwater lake conditions due to a low total inorganic carbon (TIC)
value and relatively coarse grains. The predictions are consistent with observations of
pristine sponge spicules and the pollen species Typha (i.e. cattail) in the smear slides
from the corresponding depth interval. Further observations of fluctuating levels of clay
and silt, and occasional coarse grain deposits within this zone are also present within
the smear slides, which are uniform with the Blunt (2013) study.
~*~
Foraminiferal proxies reflect changes in northeast Pacific ocean-atmospheric
circulation through the Medieval Climate Anomaly and Little Ice Age
Dorothy Paka, Ingrid Hendyb, and Arndt Schimmelmannc
a
Marine Science Institute, University of California at Santa Barbara, Santa Barbara CA
93106 (pak@geol.ucsb.edu; b Department of Geological Sciences, University of
Michigan, Ann Arbor, MI 48109 (ihendy@umich.edu); c Department of Geological
Sciences, Indiana University, Bloomington, IN 47405 (aschimme@indiana.edu)
39
An understanding of the spatial and temporal variability of late Holocene climate events
is necessary to decipher natural climate variability from anthropogenic change. High
quality sediment cores from the Santa Barbara Basin provide one of the few North
Pacific high-resolution marine records of the last 2000 years of temperature change.
Foraminiferal proxy records from these cores provide an opportunity to link marine
temperature records from the northeast Pacific to other regions, as well as with regional
continental records of temperature and precipitation.
We present an approximately annual to decadal record of size-normalized shell weight,
Mg/Ca and δ18O of the near-subsurface dwelling planktonic foraminifera Globigerina
bulloides, and δ18O and coiling of the thermocline-dwelling planktonic foraminifera
Neogloboquadrina pachyderma in Santa Barbara Basin, California (34° 16.847’ N, 120°
02.268’ W). Together, these proxies reflect changes in upper water column temperature
and salinity over the last 2000 years. Planktonic foraminiferal Mg/Ca temperatures
indicate a long term cooling trend of ~2.5 °C over the last 2000 years on the California
margin that ended around 1800 CE. The first half of the Medieval Climate Anomaly
(MCA; 500-1000 CE) was relatively warm and stable, cooling by approximately 2° C by
the by the end of the MCA (1300 CE). Mg/Ca and δ18O-water records indicate warm,
relatively saline conditions in Santa Barbara Basin during the MCA in agreement with
regional proxies of precipitation, which indicate drought conditions through much of the
MCA. These results are consistent with a greater influence of subtropical gyre water on
the California margin, particularly during the first half of the MCA.
Sea surface temperatures during the Little Ice Age (LIA; 1400-1850 CE) were highly
variable on the California margin, however, foraminiferal proxies indicate extended
periods of cool temperatures from the MCA/LIA transition until the late 18 th century.
Mg/Ca and δ18O-water records indicate that relatively cool, fresh conditions
predominated during the LIA on the California Margin, consistent with continental
records of increased precipitation, and may indicate a stronger influence of the
California Current. Coolest temperatures of the last 2000 years occurred between
approximately1825 and 1850 and from approximately 1949 to 1952. Mg/Ca derived
temperatures gradually increased after 1952, with the warmest temperatures occurring
after the mid-1970s.
~*~
Influence of the Pacific Decadal Oscillation and El Niño-Southern Oscillation on
lacustrine hydroecologic cycling in Alberta
R. Timothy Pattersona, Lisa A. Nevilleab, Paul Gammonc, Graeme T. Swindlesd, Andrew
L.Macumbera
aOttawa-Carleton
Geoscience Centre and Department of Earth Sciences, Carleton
University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6 (tim.patterson@carleton.ca,
andrewmacumber@cmail.carleton.ca); bGeological Survey of Canada, 3303 33 St.
Northwest, Calgary, AB, T2L 2A7 (Lisa.Neville@NRCan-RNCan.gc.ca) (2) cGeological
Survey of Canada, 601 Booth St. Ottawa, ON, K1A 0E4 (Paul.Gammon@NRCanRNCan.gc.ca), dSchool of Geography, University of Leeds, LS2 9JT United Kingdom
(G.T.Swindles@leeds.ac.uk)
40
High-resolution (~ 1 yr resolution) temporal variation in Arcellacea (testate lobose
amoebae) assemblages and grain-size data were documented in a freeze core record
spanning the interval AD 1875-2010 that was collected from Alberta Lake East (ALE).
Arcellaceans play a key role in aquatic ecosystems where they exert considerable
predatory pressure on bacteria and smaller eucaryotic microbes and represent an
important intermediary food web component. In Alberta they respond to nutrient
enrichment derived from sediment influxes from the catchment, and provide evidence
that lakes in the region exhibit hydroecological responses to temporal variation in
precipitation, including droughts. They are thus useful indicators of paleolimnological
and climatic change. Anthropogenic influence on this remote kettle lake has been
minimal, as there are no roads or other infrastructure within the watershed. PeakFit
analysis of the grain size data indicates that the gyttja infill of the lake has not been
significantly influenced by bioturbation, despite bottom waters being well oxygenated.
Spectral time series analysis of individual arcellacean taxa (e.g. Cucurbitella triscuspis,
a eutrophication indicator), as well as grouped difflugids (generally more sensitive to
suboptimal conditions) and centropyxids (opportunistic generalists) resulted in
identification of discontinuous cycles archived in the faunal assemblage data, which
correlate particularly well with the 2-7-year El Niño-Southern Oscillation (ENSO) and 1525 and 50-70-year modes of the Pacific Decadal Oscillation (PDO), and to a lesser
extent the 50-90-year Atlantic Multidecadal Oscillation (AMO). Wavelet time series
analysis of arcellacean assemblages indicate that the hydroecology of ALE changed
significantly when the Polar Front retreated northward across the latitude of the lake as
the Little Ice Age (LIA) drew to a close. Through the latter stages of the LIA in the late
19th century centropyxids were ecologically dominant and responded strongly to the
various climate drivers, particularly ENSO. As ALE warmed and productivity increased
through the early 20th century first difflugids and then C. Tricuspis began to out
compete the centropyxids, and in turn began to cycle according to the various
hydroecological influences of ENSO, PDO and AMO.
~*~
Impact of Increasing Temperature on Denver, CO Water Resources
Joseph E. Pearsonª, Jacqueline J. Shinkerª, Dannele E. Peckᵇ, and William J. Gribbª
ªDepartment of Geography, University of Wyoming, 1000 E University Ave, Geography
Department 3371, Laramie, WY 82071 (jpearso6@uwyo.edu); ᵇDepartment of
Agriculture and Applied Economics, University of Wyoming, Laramie, WY 82071
The South Platte River basin in Colorado provides water to much of the eastern part of
the state, including the Denver metropolitan area. The South Platte River receives most
of its annual water supply from winter precipitation, in the form of snow. Projected
future climate conditions, particularly increased temperature, will likely cause earlier
snowmelt, and thus change the timing of runoff and water delivery to downstream users.
Increased air temperature might also increase demand for water during the summer
months because of increased evapotranspiration. Population projections for Denver,
CO indicate continued increases. Changes in annual precipitation could exacerbate the
41
situation, but projections of this climate variable are highly uncertain. The objective of
this study is to assess future risks of water shortage in the Denver metropolitan area in
2050 and 2100, as compared to present. We use climate data from CMIP3, historical
water use for the Denver metropolitan area, and stream discharge data from USGS, to
form historical distributions that serve as inputs to a Monte Carlo Simulation model.
This model tracks, on a daily basis, randomly-drawn inflows to a water storage
reservoir, downstream withdrawals, and thus water storage volume (in reservoirs). It
also reports water volume in storage at the end of the year. The model’s primary output
is the estimated frequency (probability) of days in a year in which water storage volume
falls below a minimum threshold, under current versus future climate conditions. The
analysis was also repeated for three different water storage capacities to determine if
increasing storage capacity could mitigate the risk of water shortage. Results indicate
that the Denver metropolitan area will experience increased risk of water shortage in the
future. Probability of one or more days of water shortage occurring in a year increases
from 53.7% in 2010 to 79.3% in 2050, and 95.4% in 2100. Increased storage capacity
does not substantially decrease the risk of water shortage in years 2050 and 2100. Our
principle conclusion is that Denver’s future available water supply will be influenced
primarily by temperature-driven changes in the timing of runoff and the total amount of
annual precipitation, which increased storage capacity will not effectively mitigate.
~*~
Collaborative Research: Multi-century perspectives on current and future
streamflow in the Missouri River Basin
Gregory T. Pedersona, Jay Alderb, Edward Cookc, Naresh Devinenid, Jonathan
Friedmane, Steven Hostetlerb, Upmanu Lallc, Caroline Lelandc, Justin Martinf, Gregory
McCabeg, Parker Nortonh, Scott St. Georgei, Jeannine St. Jacquesj, Dave Sauchynj,
John Stammh, Erika Wisek, Connie Woodhousel
aU.S.
Geological Survey, 2327 University Way (Suite 2), Bozeman, MT 59715
(gpederson@usgs.gov); bU.S. Geological Survey, 104 Wilkenson Hall, Oregon State
University Corvallis OR 97331 (jalder@usgs.gov, swhostet@usgs.gov); cLamontDoherty Earth Observatory, Columbia University, 61 Route 9w, Palisades, NY
(drdendro@ldeo.columbia.edu, upmanulall@gmail.com, cleland@ldeo.columbia.edu);
dDepartment of Civil Engineering, Convent Ave. and 140 th St., The City College of New
York (CUNY) New York, NY, 10031 (ndevineni@ccny.cuny.edu); eU.S. Geological
Survey, 2150c Centre Avenue Fort Collins, CO 80526 (friedmanj@usgs.gov);
fDepartment of Ecology, 106 AJM Johnson Hall, Montana State University, Bozeman,
MT 59717 (martinjustintimothy@gmail.com); gU.S. Geological Survey, Denver Federal
Center, MS 412, Denver, CO 80225 (gmccabe@usgs.gov); hU.S. Geological Survey,
South Dakota Water Science Center, 1608 Mountain View, Rapid City, SD 57702
(pnorton@usgs.gov, jstamm@usgs.gov); iUniversity of Minnesota, 414 Social Sciences,
267 19th Ave South Minneapolis, MN 55455 (stgeorge@umn.edu); jPrairie Adaptation
Research Collaborative 3737 Wascana Pkwy, Regina, SK S4S 0A2
(David.Sauchyn@uregina.ca, Jeannine.St.Jacques@uregina.ca); kDepartment of
Geography, University of North Carolina at Chapel Hill, Saunders Hall, Campus Box
3220 Chapel Hill, NC 27599 (ekwise@email.unc.edu); lSchool of Geography and
42
Development 453E Harvill Building, Box #2 University of Arizona Tucson, Arizona
85721 (conniew1@email.arizona.edu)
The Missouri River Basin (MRB) is the only major river headwaters in the western U.S.
for which hydrologic reconstructions from tree rings have not been generated in any
systematic way. This knowledge gap is critical given that the region is facing an array of
water resource issues that are challenged by hydrologic variability – experiencing both
severe floods and droughts in the recent past. Providing a longer context for
understanding past variability of flow and the climatic controls on it, particularly at
decadal and longer time scales, is critical for anticipating and managing future water
supplies. Historical discharge records are too short for such assessments; hence, the
value of tree-ring based hydrologic reconstructions that span the past several centuries
to millennium. Here we present early progress in a collaborative research project that
seeks to address this data and knowledge gap by developing Hierarchical Bayesian
Models (HBM) for streamflow reconstruction on the MRB drainage network using
existing, new, and updated tree-ring collections. The HBMs will be constructed to
directly consider the spatial dependence structure of flows in the drainage network
leading to improved regional assessments of potential non-stationarity in past, present,
and projected future changes in streamflow. A variety of hydrologic, climatic, and landuse modeling experiments will also provide information on the likely drivers of historic
and future drought and pluvial events. Flow reconstructions developed using the HBM
methods will be compared to results obtained from a suite of more traditional to novel
reconstruction methods that are less complex, but offer other potential advantages such
as enhanced retention of low-frequency climate information. Reconstruction of annual
(water year) total flows and seasonal low flows will be targeted due to their importance
for navigation, reservoir operation, and environmental regulation and ecology.
~*~
The Snowmastodon Project: A view of the Last Interglacial Period from the
Colorado Rockies
Jeffrey S. Pigatia
aU.S.
Geological Survey, Denver Federal Center, Box 25046, MS-980 Denver, CO
80225; jpigati@usgs.gov
In North America, terrestrial records of biodiversity and climate change that span Marine
Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the
coupling of the ocean-atmosphere system is manifested in biotic and environmental
records and how the terrestrial biosphere responds to climate change. In 2010–2011,
construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a
nearly continuous, lacustrine/wetland sedimentary sequence that preserved evidence of
past plant and animal communities between ~140 and 55 ka, including all of MIS 5. At
an elevation of 2705 m, the Ziegler Reservoir fossil site (ZRFS) also contained
thousands of well-preserved bones of late Pleistocene megafauna, including
mastodons, mammoths, ground sloths, horses, camels, deer, bison, black bear,
coyotes, and bighorn sheep. In addition, the site contained more than 26,000 bones
from at least 30 species of small animals, including salamanders, otters, muskrats,
43
minks, rabbits, beavers, frogs, lizards, snakes, fish, and birds. The combination of
macro- and micro-vertebrates, invertebrates, terrestrial and aquatic plant macrofossils,
a detailed pollen record, and a robust, directly dated stratigraphic framework, shows
that high-elevation ecosystems in the Rocky Mountains of Colorado are climatically
sensitive and varied dramatically throughout MIS 5. Our results demonstrate the
importance of hemisphere-scale teleconnections while underpinning the fact that
regions, and even sub-regions at high elevations, may respond to changing climate
conditions in ways that are similar or different from hemsipheric or global averages
depending on whether certain environmental thresholds are met.
~*~
n-Alkanes as a Biomarker for Holocene Paleoclimate in the Tulare Lake
Catchment, California, USA
Jeremiah Reagana, Roy Lafevera, and Robert Negrinia
a Department
of Geology, California State University Bakersfield, CA 93311
JeremiahReagan@gmail.com; Department of Chemistry, California State University
Bakersfield, CA 93311 rlafever@csub.edu; Department of Geology, California State
University Bakersfield, CA 93311 rnegrini@csub.edu
Tulare Lake, a quasi-terminal lake which has a capacity of 10M km3 (~8M acre-ft), has
the potential to constrain such models. Leaf waxes from terrestrial runoff, preserved as
long chain alkanes in lake sediments, have been shown to reveal changes in
surrounding vegetation. Cores from Tulare Lake were sampled and extracted for long
chain n-alkanes (C20 – C36), and submitted to GC-MS analysis to determine
concentrations. The distributions of these alkanes are used to construct qualitative
trends of runoff and relative contribution of grasses vs trees and shrubs over the past
20k years.
A ratio of the relative values of alkane concentrations corresponding to certain odd
numbered chains [Paq=(C23+C25)/(C23+C25+C29+C31)] has been used in other studies to
estimate the relative contribution of aquatic vs terrestrial plants. For the Tulare
sediments, this ratio is almost always well above 0.3 which suggests terrestrial input
into a dominantly aquatic assemblage, a result consistent with C/N data from a prior
study on Tulare Lake. The Carbon Preference Index (CPI), reflecting the relative
abundance of odd/even chain alkanes, and, as such, an indicator of terrestrial input, has
a mean value between 1.0 and 1.5 also suggesting abundant aquatic composition of the
lacustrine organics though with a slightly more terrigenous composition.
Relative abundance of longer chains, C31 vs C29 and C27 is used to represent change in
the contribution of grasses vs. woody angiosperms to terrestrial carbon input. This
method can reveal changes, with an increase in C31/(C27+C29+C31) reflecting an
increase in grasses over woody angiosperms. Since California is deficient in C4
grasses, this is likely to anti-correlate strongly with the C3/C4 data when δ13C and δD
analyses are completed. Initial results show systematic variations in grass abundance
over time including abundant grasses during the early Holocene lake highstand
observed in lake records throughout central and southern California.
~*~
44
Western Weather and Climate during PACLIM Year 2014-15
Kelly Redmond
Regional Climatologist, Western Regional Climate Center, Desert Research Institute
Reno Nevada (Kelly.Redmond@dri.edu)
The dominant story for 2014-2015 in the western United States was the continuing
California-Nevada drought, centered on the Sierra Nevada, and now in its fourth winter.
Each of the three prior winters was dry, but background conditions were different for
each of those three years, and the seasonal traces of accumulated precipitation looked
very different from each other. The winter of 2014-2015 continued in this vein. After a
wet start in December 2014, January brought completely opposite conditions, with many
parts of California experiencing the driest January on record. An outstanding feature of
this drought is that temperatures have been higher than in previous droughts. Calendar
year 2014 was the warmest in the last 120 years in California, considerably above
second place. The winter of 2014-2015 has been very warm, especially at higher
elevations, at or above all previous years in many places in the West. Since the start of
2014, every month in California has been warmer than average. The warm conditions
over the winter of 2014-2015 have led to a “snow drought” in many western states,
whereby precipitation since the start of Water Year 2015 in October 2014 has been
above average, but snowfall and snowpack are well below average. This has important
ramifications for streamflow. As of the end of February, projected Colorado River
snowmelt inflow to Lake Powell stood at about 73 percent of average. Without a wet
spring this will cause additional drops in Lake Mead and Lake Powell, the two largest
reservoirs in the United States. Also particularly striking during the winter of 2014-2015
has been the nearly continuous east-west contrast in United States temperature, very
cold in the east, and very warm in the mountain states. Alaska as well has shared in
the warmth of western North America. Another outstanding feature has been the
presence of very warm ocean water along the entire West Coast of North America, with
many biological effects being noted. At times this warm ocean water has extended
across the Pacific to eastern Asia. Other aspects of the climate of the past year in the
West and along the West Coast will be reviewed as well.
~*~
Constraining the season of occurrence and impacts of the Mazama Ash:
evidence from a laminated marine sediment core from the NE Pacific
Helen M. Roea and Karen R. Logana
School of Geography, Archaeology and Palaeoecology, Queen’s University of Belfast,
Belfast, BT7 1NN, United Kingdom (h.roe@qub.ac.uk)
a
Tephra deposits from the eruption of Mt Mazama, Oregon at ca. 6,730 14C yr BP have
been widely reported in sediment records from the western United States and
45
southwestern Canada, and the ash layer represents one of the most important
stratigraphic markers for the mid-Holocene in western North America. In spite of a
substantial literature on the ash, there remain uncertainties about the character and
distribution of the tephra fall-out and the climatic impacts of the ash. In this paper we
present the results of a very high-resolution study of a diatomaceous marine sediment
core (MD02-2494) from Effingham Inlet, SW Vancouver Island, British Columbia,
spanning the interval of the ash. The sediments were deposited under anoxic
conditions, are well laminated and preserve a seasonal to sub-seasonal record of
primary productivity change, permitting clear delineation of the season of tephra
deposition. Scanning Electron Micrographs reveal that the lower boundary of the ash is
sharp, suggesting sudden inundation and highlighting a lack of bioturbation and
sediment reworking. The ash was deposited as a discrete unit, with little interspersed
within it except for some Chaetoceros affinis resting spores and Chaetoceros vegetative
cells. This indicates that the ash was deposited en masse rather than gradually or in
stages. The volume of ash in the core suggests that the ash probably restricted light
availability in the water column and temporarily suppressed primary productivity until it
descended through the photic zone. Diatom analyses further confirm that prior to the
ash-fall, climate was characterised by warm, dry conditions with significant autumn
productivity. However, a wet-shift occurring around the time of ash deposition can be
inferred. The presence of the Mazama ash in Effingham Inlet has redefined the known
boundaries of the ash-fall in the NE Pacific region, which has not previously been
documented this far northwest of the source.
~*~
The California Drought of 2012-20xx; How Is the 2015 Water Supply Shaping Up?
Maury Roos
California Department of Water Resources, PO Box 219000, Sacramento CA 95821
(mroos@water.ca.gov).
We won’t know the outcome for another couple of months, but, as of mid-February, the
outlook for an end to the California drought is not bright. WY 2015 is wetter than 2014
but so far not enough for recovery from the current drought.
First, some background. Most of the water supply in California is in the north.
About ¾ the average natural runoff occurs north of Sacramento. However, around
80 percent of the water needs for irrigated agriculture and urban usage is south of
Sacramento and our Sacramento San Joaquin Delta junction of the two major Central
Valley rivers. That is one of the reasons for embarking on major water projects to
transfer water from the north to the south and from east to west for urban users. Our
rainfall and runoff is also highly variable from one year to the next, which is ameliorated
by approximately 43 million acre-feet of reservoir storage capacity. The mountain
snowpack is also important and furnished about 15 million acre-feet of natural storage
on average historically, but is maybe 10 percent less now due to global warming.
In general, since year 2000, which ended a run of wet years, we have seen quite
46
a few dry years. There was the 2007 – 09 three year drought, then a couple of wetter
years followed by 3 dry years, 2012-14, a more severe drought. Calendar year
2013 was one of the driest in the record. Near the end of January 2014, we had seen
13 months of dryness. Then some rains came in February and March which eased the
situation some. However, there was insufficient water in the USBR reservoirs in
northern California to provide San Joaquin Valley Delta Mendota Exchange Contract
water user their usual supplies from the Delta and they turned to their original prior
water rights on the San Joaquin River, which left nothing for the Friant Kern Canal users
on the east side of the Valley south of Fresno, an area with many orchards. Some
water was traded at expensive prices and those who had wells pumped additional
ground water which contributed to further water level decline. Continued severe drought
this year will be disastrous.
Good rains in December, 2014, generated some optimism, but January 2015 was
probably the driest of record. One atmospheric river (pineapple express) storm in early
February was productive in the north, but lighter in the southern Sierra.
Then dryness set in, raising concerns of a 4th year of drought.
Not many historical droughts exceeded 3 years in length. But there are two
Notable 6 year droughts: 1929-34, which became the design period for the CVP and
SWP planning, and the more recent 1987-92 period. Also of note was the severe
2 year 1976-77 drought. WY 1977 was our driest runoff year, slightly worse that the
1924 drought. This past year, as a single year, would rank 3 rd driest in northern
California runoff. The 3 year period, 2012 -14 would generally be considered 3rd worst
for the Sacramento River system and also the combined 8 river system. However, on
the San Joaquin River, the estimated recent 3 year natural runoff was the lowest of
record, slightly exceeding the previous 1929-31 dry sequence. Overall, this drought has
been more severe across the middle of the state--the San Joaquin Valley and southern
Sierra and the Central Coast regions.
The snow pack this season has been dismal at this point. An average pack would
contain about 29 inches water content near the end of March, which is usually the time
of maximum accumulation. This year’s snowpack, according to automatic sensors, was
only about 6 inches statewide in mid-February. This is similar to that of 1977, our driest
year, and last year, 2014. The reason that the snow percentages this year are so far
behind the precipitation accumulation is a combination of warmer temperatures during
the two big storms and warmer mountain temperatures afterward which caused early
melting of what snow there was in the lower snow zone.
We still have about one quarter of the wet season left, which gives hope for some
improvement. The northern Sacramento River region is better than last year, but the
middle remains dry as of this writing.
~*~
47
Are Mid-winter Droughts in Northern California Increasing?
Maurice Roos
California Department of Water Resources, PO Box 219000, Sacramento CA 95821
(mroos@water.ca.gov).
The major portion of northern California annual precipitation comes during the winter.
Mid-winter dry spells can lead to shortfalls in snowpack and water supply. Recent
decades have led to questions about a possible change in patterns leading to more
drought years. In this paper two widely used mountain precipitation indexes were
examined to see if a trend exists for increasingly dry winter months. There does seem
to be evidence for some increased risk of dry winter months in the last 30 years, more
so in the northern Sierra than in the south. Results are presented in this paper for the
Northern Sierra 8 station index and the San Joaquin 5 station index.
~*~
Does climate need to vary before carbon and nitrogen ratios change in desert
lakes? Examples from Big Soda and Pyramid Lakes.
Michael R. Rosena and Liam Reidyb
aUS
Geological Survey, 2730 North Deer Run Road, Carson City, Nevada 89701
(mrosen@usgs.gov) bUC Berkeley, Department of Geography, 507 McCone Hall,
Berkeley, California, 94720
Climate change has been invoked as the reason that carbon:nitrogen (C:N) ratios
change in lakes as lower lake levels allow more land-based organic matter to enter the
lake basin or higher lake levels allow more autochthonous production of carbon within
the lake. Sediment cores representing the last 1500 years from Big Soda Lake, a small,
deep, hypersaline meromictic lake in the Carson River basin and Pyramid Lake a large
deep, hyposaline lake in the Pyramid Lake basin of Nevada show minimal change in
C:N ratios, 15N, and 13C while other measures of climate such as 18O isotope values
do change. In the past 100 years, when significant hydrological changes have occurred
in both lakes due to the diversion of water from the Pyramid Lake basin to the Carson
River basin for irrigation water use, C:N ratios have decreased in both basins, while
isotopic compositions have changed in opposite directions in each lake. The change in
isotopic compositions is likely due to the fact that the lake level in Big Soda Lake has
risen while the lake level in Pyramid Lake has fallen. Given these opposite changes in
lake level, C:N ratios would also be expected to change in opposite directions.
However, Pyramid Lake went from an overflowing lake system to a closed basin
between 1905 and the late 1930s, which possibly induced more autochthonous
production of carbon even though lake level fell. In Big Soda Lake, the increased input
of fresh groundwater produced meromictic conditions and stimulated autochthonous
diatom production which also decreased the C:N ratio. Although climate change can
cause shifts in C:N ratios in lakes, in these two arid zone lakes, changes in hydrology,
48
unrelated to climate change appears to be more important than small (<100 year)
climate related changes in the last 1500 years.
~*~
Paleomagnetic Secular and Environmental Magnetism Variation of Late Holoceneaged Sediments of Tulare Lake, CA
Janine Rozaa, Brandon Jacksona, Eric Heatona, Rob Negrinia
aCalifornia
State University, Geological Sciences, Bakersfield, California 93311, USA
(janine.roza@gmail.com)
The lake-level record from Tulare Lake has been shown to potentially provide valuable
constraints on forecasting runoff from the Sierra Nevada over the next several
generations into the San Joaquin Valley of California, one of the world’s most prolific
agricultural centers. This project focuses on the magnetic properties of Tulare lake
sediments in an attempt to date a new sedimentary record, with which to test earlier
work done on this lake. Toward this end, four trenches were dug at two localities in the
southern end of the Tulare lake bed, totaling approximately six meters in depth. Each
trench was sampled at two-centimeter spacing. The samples were analyzed at the UC
Davis Paleomagnetics Laboratory and the Institute for Rock Magnetism in Minneapolis
for both remanence directions and magnetic properties. For both sites, the location of a
major unconformity is identifiable by changes in the temperature dependent
susceptibility above and below the unconformity. The magnetic properties measurement
system (MPMS) data indicates the presence of magnetite and goethite at both sites, but
that there is less magnetite at the Atwell Island site. The ARM/IRM data for both sites
decreased upsection toward the unconformity indicating an increase in magnetic grain
size that may be reflective of bulk grain size as the lake shallows. The Day plots also
indicate larger grains with more multi domain characteristics at the Atwell Island site
than the samples from the Poso Canal site. The reduced amount of magnetite and the
larger grain size, perhaps indicating a shift toward multi-domain behavior, may help to
explain why the paleomagnetic secular variation dating was unsuccessful at the Atwell
Island site. The paleomagnetic results at the Poso Canal site indicate that some of the
deepest trench sediments were deposited in the age range of 7200-6300 C14 years
(~7,000 to 8,000 cal yr B.P.) ago, and the youngest sediments were deposited
approximately 1900-500 C14 years ago. Sediments of this age are consistent with
relatively high lake levels during these times as suggested by earlier studies.
~*~
Glaciogenic effects during MIS 2 on the lacustrine sediment flux of Tulare Lake.
Lilian Rubia, Matthew Van Grinsvena, Robert Negrinia, and Magdalena Juareza
aCalifornia
State University Bakersfield, Department of Geological Sciences,
9001 Stockdale Highway, Bakersfield, Ca. 93311 (lrubi08@csu.fullerton.edu).
49
Physical and chemical changes in the lithology of deposited sediment can act as
proxies for past lake levels and, hence, climate change, particularly when terminal lake
basins are studied. Ever since the MIS 2 glacial maximum one such lake, Tulare Lake,
CA, has been the terminus of four of the largest rivers from the southern Sierra Nevada
Mountains and hydrologic modeling has shown that its surface elevation is a good
gauge of Sierran stream discharge. Here we present two chronologies which extends
the relative paleolake-level record of Tulare Lake from the TL05-4 cores based on
geochemical and geophysical proxies back to 29 or 44 cal kyr BP. Proxy data from
these cores include magnetic susceptibility, grain size, total inorganic and organic
carbon, and carbon-nitrogen ratios. To some extent, these data co-vary and based on
comparisons with earlier trench sample based lake-level records, reflect relative lake
level. The earliest part of the record shows millennial scale cyclic fluctuations of grain
size which may relate to regional climate. After this, Tulare Lake experienced a sharp
increase in lake level, likely associated with the creation of a small fan dam around 25
cal kyr BP. Lake level gradually decreased during the Tioga Glaciation (25-15 cal kyr
BP). This may have been caused by decreased summer precipitation and winter
precipitation that has been sequestered in the snowpack. During the late Tioga
Glaciation, large amounts of runoff from the melting glaciers and addition of water from
the Kings River filled the lake and significantly increase the sill height of the fan dam
(18.6-15 cal kyr BP) to more or less present elevations. After this, Tulare Lake levels
stabilized and varied in conjunction primarily due to changes in sea surface
temperatures. Lack of age control prior to 24 cal kyr BP leaves some ambiguity between
age models, both of which have merit. Further age dates are expected to refine the
model and extrapolate lacustrine sediment changes to regional climate change.
~*~
Fast and economical sampling and resin-embedding technique for small cores of
unconsolidated, fine-grained sediment
Arndt Schimmelmanna, David J. Riesea, and Juergen Schiebera
a
Department of Geological Sciences, Indiana University, IN 47405
(aschimme@indiana.edu)
An economical and fast water-acetone-epoxy-exchange method is presented for resinimpregnation and subsequent imaging of sedimentary structures in fine-grained
unconsolidated sediment. The method is useful for documenting small-scale textural
features that are difficult to preserve in sediment, such as lamination and bioturbation
features. Advantages are (i) the reduced use of solvents and reagents; (ii) minimal
disruption of sedimentary structures; and (iii) increased speed of epoxy resin
impregnation. The sampling apparatus consists of a sampling tube of stainless steel
twill weave with a diameter of ~1 cm in a rigid brass tube holder. The sample tube
assembly is inserted slowly into the unconsolidated sediment, followed by plugging the
bottom with a soft wax disk. The sampling tube filled with sediment is removed from the
holder and placed vertically into a container for step-wise exchange of saline interstitial
water with deionized water, then with acetone, and finally with low-viscosity Spurr epoxy
resin. A peristaltic pump circulates the resin from the bottom of the glass apparatus onto
50
an exposed strip of filter paper above the glass apparatus for rapid evaporative removal
of acetone. The devolatilized resin drips back into the glass apparatus. Only a limited
volume of resin is needed, especially when multiple sediment cores are treated
simultaneously in batch mode. Circulation is terminated after 3 days when the cores are
taken out of the resin bath and left standing upright in air for a few days for final
evaporation of acetone. Curing of the Spurr resin occurs at 60°C for a week. The
method lends itself for generating thin-sections and specimens for optical, SEM and
TEM imaging not only of sediments, but also for biological tissues and other specimens
that can be housed in stainless steel mesh capsules and tubes.
~*~
Climatic controls of early snowmelt runoff and late-season drought in the upper
South Platte River basin and metropolitan Denver
Jacqueline J. Shinkera and Joseph E. Pearsona
aDepartment
of Geography and Roy J. Shlemon Center for Quaternary Studies,
University of Wyoming, Laramie, WY 82071 (jshinker@uwyo.edu)
The snow-fed South Platte River contributes a majority of the water supply for the
Colorado front range, including the Denver metropolitan area. The headwaters of the
South Platte River, like many localities in the interior intermountain west, receives a
majority of its water resources from winter snowpack. While increasing spring
temperatures has led to early onset of stream runoff throughout the region, the high
degree of variability in precipitation also plays an important role in terms of moisture
availability and persistence of drought later in the summer months. For this study, we
use stream discharge data from the United States Geological Survey to identify years of
abnormally early stream flow timing in the last three decades for the upper South Platte
River basin above Denver, CO. A time series was constructed to identify years with
abnormally early snowmelt timing at the 25, 50, and 75 percent quartiles of annual
discharge. These three quartiles explain entire snowmelt runoff and allow for a better
understanding of the climatic controls responsible for stream discharge, and thus water
availability, throughout the year. Based on the stream discharge data, selected years
were identified that represent basin-wide early stream discharge cases at each quartile.
We use the 32-km gridded North American Regional Reanalysis data set to make
composite-anomaly maps to identify and explain the spatial and temporal climatic
controls impacting stream discharge during the selected years. A combination of higherthan-normal springtime temperatures appears to drive early snowmelt at the 25th
percent quartile. However, processes that govern precipitation (e.g. moisture
availability, and atmospheric circulation) appear to be controlling factors later in
summer. Our results indicate that both warmer-than-normal temperatures, especially in
spring, in conjunction with available atmospheric moisture and circulation processes in
summer contribute to overall reduced water resources in the region. A better
understanding of the impact that multiple climate conditions have on the timing of
snowmelt, and corresponding stream flow discharge, is crucial for informing water
resource planning/decisions in the changing climate of the future.
~*~
51
Sagebrush Fire History at Redfish Bog
Victoria M. Simmonsa, Andrea Brunelleb, Isaac Hartc
aDepartment
of Geography, University of Utah, Salt Lake City, UT 84112
(victoreos.simmons@gmail.com), bDepartment of Geography, University of Utah, Salt
Lake City, UT 84112 (andrea.brunelle@geog.utah.edu), cDepartment of Anthropology,
University of Utah, Salt Lake City, UT 84112 (ikeosaurus@gmail.com)
The purpose of this project is to reconstruct the Holocene fire history of the Deep Creek
Mountains in western Utah. To accomplish this we conducted charcoal and pollen
analysis to determine what the paleoclimatic history would be of this area. The first step
was to evaluate charcoal abundance in a 93 cm sediment core taken in October 2013
from a site on Goshute Reservation lands in the southern Deep Creeks. The site
investigated is Redfish Bog, which is a wet meadow and spring at 2769 meters. This
study is part of a broad research agenda aimed at understanding fire histories and
vegetation dynamics in sagebrush environments.
Charcoal analysis was done over Spring Semester 2014. Peaks in the data indicate that
a distinct change or disturbance occurred in the fire pattern and further research will be
done to determine what the cause was. The highest peaks occur in the upper 1/3 of the
core, with the background of the core having a pattern of variability. Using charcoal to
elucidate the fire record of this region will provide a better understanding of the
connection between fire, climate and fuel availability. Radiocarbon dating was done on
sample 85-86 cm, and a calibrated date of 17000 years BP was discovered.
The second step of the project was analysis of fossil pollen to determine what
vegetation was present through the site’s history. Pollen in the upper 1/3 of the core
was analyzed and no distinctive change of vegetation has occurred, this was to be
expected, as the vegetation should be consistent throughout this most recent time
period. Additional pollen analysis will occur on the last 2/3 of the core in which we do
expect to see the fuel type change from tree-dominated vegetation to shrub/herb
dominated. Relationships between fires and their environments are not always easy to
understand, but by evaluating this unique environment we hope to gain some
perspective on the fire story of this region.
~*~
The Geochronologic and Paleontologic Framework of the Late Pleistocene Tule
Springs Fossil Beds National Monument
Kathleen Springera,b, Craig R., Mankera,b, Eric Scotta, Jeffrey S. Pigatib, and Shannon
Mahanb
aSan
Bernardino County Museum, Redlands, CA 92374; bU.S. Geological Survey,
Geologic Division, Denver Federal Center, Denver, CO 80225
In December 2014, a total of 22,650 acres of the upper Las Vegas Wash, in the
northern Las Vegas Valley, was designated Tule Springs Fossil Beds National
Monument. The new monument fills a gap in the National Park Service fossil record as
the first site in the U.S. that is specifically dedicated to preserving and interpreting
52
Pleistocene paleontology. The Tule Springs local fauna (TSLF), one of the most
significant late Pleistocene vertebrate assemblages in the American Southwest, is
entombed in fine-grained ground-water discharge deposits (desert wetlands) throughout
the upper Las Vegas Wash. The San Bernardino County Museum, concertedly working
in the area since 2001, initiated a large-scale paleontology and geologic investigation in
2008 that has resulted in the discovery of hundreds of fossil localities and thousands of
fossil specimens, greatly extending the geographic and temporal footprint of earlier
investigations from the 1960’s. Mammuthus, Camelops, Equus and Bison dominate the
fauna. Megafaunal carnivorans including Panthera and Smilodon are present, along
with smaller organisms, including amphibians, snakes, and birds and micromammals.
Investigations focused on detailed geologic mapping and targeted dating with the goal
of establishing the context for the fauna and integrating the TSLF into a rigorous
lithostratigraphic and geochronologic framework. We established a highly resolved
chronology based on 14C dating of charcoal and luminescence dates (in collaboration
with the USGS) and have documented the most comprehensive record of ground-water
discharge deposits anywhere in the world. We also redefined and established new
geologic units within the informally named Las Vegas Formation. Our results show that
ground-water discharge deposits in the region record dramatic hydrologic changes in
response to abrupt climate oscillations during the late Pleistocene, including the
repeated growth and collapse of entire wetland systems. The hydrologic response of the
paleowetlands documented here demonstrates a tight correlation with Greenland/North
Atlantic climate proxy data on a sub-millennial scale. Tule Springs Fossil Beds National
Monument preserves the lynchpin deposits in the Upper Las Vegas Wash for posterity,
and our scientific results provide a powerful interpretive springboard for the new
monument.
~*~
Diatom-inferred Holocene record of moisture variability in Lower Bear Lake, San
Bernardino Mountains, California, USA
Scott W. Starratta, and Matthew E. Kirbyb
aUS
Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025; bDepartment of
Geological Sciences, California State University, Fullerton, CA 94551
Holocene diatoms present in Lower Bear Lake sediments, provide a 9,200-year
hydroclimatological record for the San Bernardino Mountains in southern California.
Based on several physical and chemical properties as well as gastropod and ostracod
assemblages, Kirby et al. (2012) inferred nine (five major (PE-V to PE-I), four minor
(PE-IIIa-c, PE-IIa) decadal to multi-centennial pluvial episodes, associated with
atmospheric rivers, in sediment core BBLVC05-1 (34o15’20” N, 116o55’20” W; 4.5 m
length). The new diatom data allows evaluation of these pluvial events, as well as
detailing changes in lake surface water properties. The diatom record shows a gradual
increase in salinity during the Holocene, corroborating the inference of decreasing lake
size made by Kirby et al. (2012). The longest pluvial episode (PE-V; 9170?-8250 cal yr
BP), is dominated by fragilaroid taxa, indicating fresh, slightly alkaline waters. An
increase in halophilic taxa at ~8,700 cal yr BP suggests a several-decades-long drier
53
interval within the pluvial. PE-IV (7,000-6,400 cal yr BP) is dominated by benthic taxa,
including relatively high numbers of epiphytic taxa, indicating an increase in aquatic
macrophytes. The abundance of Aulacoseira in PE-IV and PE-III (3,350-3,000 cal yr
BP) suggests increased turbulence due to increased storminess. PE-III and PE-II (850700 cal yr BP) contain greater abundances of benthic (epiphytic) and halophilic species,
although the latter never dominate the assemblage, suggesting that the lake was
smaller than during the previous pluvial episode and that the abundance of aquatic
macrophytes was higher. PE-I (500-476 cal yr BP) was not sampled. Aerophilic taxa
comprise up to 3% of the assemblage during pluvial events suggesting increased
erosion during those periods, and the presence of symbiotic species throughout the
record indicates nitrogen-depleted waters. Greater abundance of assemblages
dominated by freshwater diatoms generally corresponds to pluvial events identified by
other proxies. Furthermore, the diatom data suggest Lower Bear Lake likely diminished
in size through the Holocene becoming more saline in the late Holocene. This decrease
in size may have been a response to an insolation-forced decrease in winter season
precipitation with a negligible contribution from the North American Monsoon.
Kirby, M.E., Zimmerman, S.R.H., Patterson, W.P., Rivera, J.J., 2012, A 9170-year
record of decadal-to-multi-centennial scale pluvial episodes from the coastal southwest
United States: A roll for atmospheric rivers?: Quaternary Science Reviews, v. 46, p. 5765.
~*~
Aridity, monsoon strength and the Little Ice Age: a 600-year record from northern
Vietnam
Lora R. Stevensa, Tracey La Roccoa, Mounga Nonua, AJ Whitea
Department of Geological Sciences, California State University, Long Beach
(lora.stevens@csulb.edu)
The Asian monsoon system is known to fluctuate in intensity over millennial time scales.
It has been suggested that during the Little Ice Age, the Southeast Asian summer
monsoon and East Asian summer monsoon (EASM) were generally weaker due to
decreased insolation. This decreased intensity should result in drier summer conditions
throughout most of southern China and northern Vietnam.
To examine this possibility, a sediment core, 1.5 m in length, was collected from Ao
Tien, Vietnam. Ao Tien (22° 26’ 54” N, 105° 37’ 02” E) is a small sinkhole in the karst
region of Bac Can Province. It is hydrologically connected via fractured limestone to a
larger lake, Ho Ba Be, and the Nang River. The lake has a maximum depth of 10 m
and high oxygen demand in the hypolimnion. It is anoxic below 4 m depth, and the
sediment preserves alternating packets of homogenous and laminated sediment.
Oxygen isotopic analyses of endogenic calcite in the lake basin indicate a significant 3
‰ shift over the last 600 years. Highest δ18O values occur from AD 1350 to 1500 and
are interpreted as a weak summer monsoon with drier overall conditions. A steady
decrease in δ18O values from AD 1500 to 1800 is interpreted as a gradual strengthening
of the monsoon, resulting in peak wet conditions in the early to mid-1800s.
54
Although these results are apparently counter to the model of a weak summer monsoon
during the Little Ice Age, they are consistent with speleothem data from eastern China.
These data suggest a weak East Asian summer monsoon (EASM) and drier conditions
during Phase 1 of the Little Ice Age (AD 1250-1550) and a stronger EASM and wetter
conditions during Phase 2 of the Little Ice Age (AD 1550-1850). Thus, Ao Tien, the
southernmost site within the EAM, shows identical changes in aridity with mid-latitude
Chinese sites.
~*~
Adaptive water resource planning in the South Saskatchewan River Basin: use of
scenarios of hydroclimatic variability and extremes
Jeannine-Marie St-Jacquesa, David J. Sauchyna, Elaine Barrowa, Michael W. Nemethb,
Ryan J. MacDonaldb, A. Michael S. Sheerc, and Daniel P. Sheerc
aPrairie
Adaptation Research Collaborative, 3737 Wascana Parkway, University of
Regina, Regina, Saskatchewan S4S 0A2, Canada (email/St-Jacques
jmcheval@sympatico.ca); bWaterSMART Solutions Ltd., Calgary, Alberta T5J 3G2,
Canada; cHydroLogics Inc., 10440 Shaker Drive Suite 104, Columbia, Maryland 21046,
USA.
The South Saskatchewan River Basin is Canada's most threatened river, with water
supplies in most sub-basins over-allocated. In 2013, stakeholders representing diverse
interests from irrigation districts, environment, municipalities, etc. created the South
Saskatchewan River Basin (SSRB) Adaptation to Climate Variability Project to explore
opportunities to improve the resiliency of the management of the Oldman and South
Saskatchewan River Basins. Streamflow projections for 2025-2054 were derived by
regressing historical river flows against climate indices and then running these statistical
models using projected climate indices from global climate models. Presented with
projections of future hydroclimate, and the simulated impacts of some of the most
extreme scenarios, plus stakeholder observations, the project participants proposed and
evaluated potential risk management and adaption strategies, e.g., optimizing existing
infrastructure, building new infrastructure, changing operations to supplement
environmental flows, reducing demand and sharing supply. This was done with a massbalance OASIS (Operational Analysis and Simulation of Integrated Systems) model
applied interactively at live modelling sessions with stakeholders through a process
designed to identify and explore practical adaptation strategies based on the best data
and knowledge in the river basins. Our results showed that forecast-based rationing
together with new expanded storage dramatically reduces shortage days.
~*~
Proxy validation: comparisons of a tree-ring inferred climate reconstruction to
Fort Snelling early climate data and high-resolution pollen-inferred climate
reconstructions from varved Lake Mina, Minnesota, USA
Jeannine-Marie St-Jacquesa, David Sauchyna, Jessica Vanstonea, James Dickensona,
Brian Cummingb and John Smolb
55
aPrairie
Adaptation Research Collaborative, 3737 Wascana Parkway, University of
Regina, Regina, Saskatchewan S4S 0A2, Canada (email/St-Jacques
jmcheval@sympatico.ca); bPaleoecological Environmental Assessment and Research
Lab, Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
A vital component of paleoclimatology is the validation of paleoclimatological
reconstructions. Unfortunately for proxy validation, there is scant instrumental data prior
to the 20th century available for the validation of reconstructions. Hence, in practice, we
typically do long-term validation using other proxy-inferred climate reconstructions. Here
we compare a three-century tree-ring inferred effective moisture reconstruction based
upon sites in Minnesota (e.g., Itasca Park) and the Dakotas to 19th century climate data
from nearby Fort Snelling, Minnesota. We also compare our reconstruction to a longer
high-resolution pollen-inferred reconstruction of effective moisture from Lake Mina,
Minnesota. The Lake Mina pollen record is dated by a varved-sediment chronology and
sampled at a four-year resolution. The pollen-based climate reconstructions are based
upon an early-European settlement period pollen-climate calibration set in order to
minimize signal distortion and bias from the severe anthropogenic disturbance that has
impacted the Midwest: selective logging, fire suppression, deforestation and agriculture.
Both proxy reproductions are shown to have problems: The tree-ring reconstruction is
biased towards drier conditions and poorly reproduces wet periods. The pollen
reconstruction has attenuated high-frequency response and some errors in the varve
chronology.
~*~
Impacts of the PDO and ENSO on Canadian Western Interior Annual and Peak
Flows
Jeannine-Marie St-Jacquesa, Sunil Gurrapua, David Sauchyna, Kyle Hodderb and Yang
Zhaoc
aPrairie
Adaptation Research Collaborative, 3737 Wascana Parkway, University of
Regina, Regina, Saskatchewan S4S 0A2, Canada (email/St-Jacques
jmcheval@sympatico.ca); bDepartment of Geography, University of Regina, Regina,
Saskatchewan, Canada; cDepartment of Mathematics and Statistics, University of
Regina, Regina, Saskatchewan, Canada
The hydroclimate of the Canadian Prairies is strongly influenced by atmosphere-ocean
oscillations such as the low-frequency Pacific Decadal Oscillation (PDO) and the higherfrequency El Niño-Southern Oscillation (ENSO). Using composite analysis, we detected
the impacts of the PDO, the North Pacific Index (NPI), ENSO and the Pacific North
American mode (PNA) on mean daily discharge from naturally-flowing rivers over the
entire Canadian Prairie Provinces. There are increased flows during the negative
phases of the PDO and PNA, La Niña events and weak Aleutian lows, and decreased
flows during the positive phases of the PDO, El Niño and strong Aleutian lows. A much
weaker effect of the Arctic Oscillation (AO) was detected. The ~60-year cycle of the
PDO has important implications for the recognition of emerging trends in streamflow in
response to global climate change as the transient trend from PDO phase can be
confounded with any emerging trends.
56
We also show how flood risk in southwestern Canadian Prairies rivers is modified by the
low-frequency PDO and higher-frequency ENSO. Daily averaged annual peak flow
records were stratified according to PDO phase and ENSO state and fit by a LogPearson III (LP3) distribution. Flood risk at most gauges was observed to be
significantly different in the two phases of the PDO. Less significant differences were
seen with ENSO. To remove the effects of sampling error and unequal lengths of time
series, a regional index approach was employed to confirm higher flood flows in the
negative phase of the PDO and during La Niña events. Also, PDO phase modulates the
effects of ENSO; i.e., floods during La Niña events occurring during the negative PDO
phase have higher magnitudes than floods during La Niña events occurring during the
positive PDO phase.
~*~
Replicating weather station air temperature measurements and monitoring snow
cover across palaeorecord sites in complex terrain in the Walker Basin,
California-Nevada
Scotty Strachana, Constance I. Millarb
a Department
of Geography, Mail Stop 154, University of Nevada, Reno, NV 89557,
USA (scotty@dayhike.net); b Sierra Nevada Research Center, Pacific Southwest
Research Station, USDA Forest Service, 800 Buchanan Street, Albany, CA 94710, USA
(cmillar@fs.fed.us)
Scientific studies across landscape or watershed scale areas often include some
component of air temperature as an indicator or response variable. In many cases, this
value is obtained from gridded models such as Daymet or PRISM, or remotely-sensed
data such as Land Surface Temperature (LST). It is increasingly possible to deploy
cost-effective in-situ sensors to monitor air temperature at sub-daily timesteps in order
to obtain more precise measurements of variability across time and space. Method of
air temperature measurement using low-cost distributed sensors varies between
published studies, with the primary differences being radiative shielding and placement
relative to ground surface and vegetation. In order to assess in-situ conditions relative to
‘standard’ 1.5 – 2 m height weather station measurements and gridded products derived
from such records or calibrated by them, a method of deployment was developed for a
palaeo and modern climate study in the Walker Basin of Nevada-California. Sensors
were fielded across 16 tree-ring sites in 4 mountain ranges, as well as co-location with
research-grade instruments to verify accuracy of the method. Each tree-ring site
contained a central ‘standard’ air temperature measurement in the canopy interspace as
well as distributed sensors within the canopy above and below the elevation of the
central sensor. Ground-level sensors to detect snow presence/absence were also
placed across each site, to compare with local SNOTEL observations as well as gridded
snow data products. Because palaeorecord study sites are often located in topographic
settings that are not complimentary to SNOTEL stations, directly observing the timing of
snow cover across aspects is seen as a check on interpolated products. Data
comparing the sensors at the site scale as well as across the watershed are presented
for one water-year of observation.
~*~
57
The extraordinary California drought of 2012-2015: Historical context and the role
of climate change
Daniel L. Swaina, Danielle Toumaa, Deepti Singha, Michael Tsianga, Matz Haugena,
Alison Charlanda, Bala Rajaratnama,b,c, Noah S. Diffenbaugha,b
aDepartment
of Environmental Earth System Science, Stanford University, 473 Via
Ortega, Stanford, CA 94305. bWoods Institute for the Environment, Stanford University,
473 Via Ortega, Stanford, CA 94305. cDepartment of Statistics, Stanford University, 390
Serra Mall, Stanford, CA 94305
California is currently experiencing its most severe drought in the observational record,
which has already resulted in widespread adverse impacts upon both human and
natural systems. Fueled by a combination of large multi-year precipitation deficits and
extremely warm temperatures, the ongoing drought has been characterized by an
unusually persistent pattern of atmospheric circulation over the northeastern Pacific
Ocean. While such an atmospheric configuration does occur periodically in the context
of natural climatic variability over the North Pacific, there is evidence that the likelihood
of persistent high pressure events in this region—similar to those which have recurred
during the 2012-2015 event—has increased due to global warming. Additional evidence
strongly suggests that the risk of “hot droughts” in California—during which periods of
low precipitation and high temperatures coincide—has already increased substantially
due to global warming. Thus, we conclude that at least some aspects of the ongoing
drought event likely have a traceable human footprint.
~*~
Reconstructing conditions for Fremont Zea mays horticulture
Marcus J. Thomson, Glen M. MacDonald
Department of Geography, University of California, Los Angeles, LA, CA 90095
(zizroc@ucla.edu) (macdonal@geog.ucla.edu)
The Fremont were maize-growing Native American peoples living in Utah between the
8th and 14th centuries AD. Archaeologists have long debated the reasons for their
mysterious disappearance prior to the arrival of the Spanish in the New World.
Demographic fluctuations, as approximated by dated archaeological sites, coincide with
large scale changes in the reconstructed climatic regime for the Southwest. Roughly
speaking, the Fremont appear to fluoresce during the Medieval Climate Anomaly (MCA,
or Medieval Warm Period) and decline with the transition from the MCA to the so-called
“Little Ice Age” (LIA). On close inspection, differences in site occupation indicate a more
complex pattern than given by a narrative of en masse regional abandonment. We are
investigating the utility of spatially downscaled temperature models to reconstruct local
conditions for dryland maize farming. We are testing our reconstructions with proxies
from subalpine lake sediment cores from Dixie, Manti La Sal, and Ashley National
Forests. We present the results of preliminary investigations of these lake cores.
~*~
58
Low cloud/fog-mediated summertime maximum temperature reductions in
Central Coastal California.
Alicia Torregrosaa, Jeff Petersa, Lorraine Flintb, Alan Flintb, Cindy Combsc
aUSGS
Western Geographic Science Center, bUSGS CA Water Science Center
Institute for Research in the Atmosphere
cCooperative
We use the 10 year, hourly, summertime (June, July, August, September) low cloud and
fog (LCF) product derived from Geostationary Operational Environmental Satellite
(GOES) imagery archives at the Cooperative Institute for Research in the Atmosphere
(CIRA) to quantify average diel, monthly, and summertime reduction in maximum
temperatures from LCF across a central California landscape. The CIRA product
differentiates warm low clouds from colder high clouds for both night and day hours for
5 summers (1999 – 2005) using a threshold compositing technique on the visible
channel and 2 near-infrared channels (3.6 μm) and (10.7 μm). Results show that the
central CA coast is cloudy on average 2 – 22 hours/day during the summer with high
clouds present only 1.64% of the summer. Based on these results we used the
undifferentiated cloud data from 1999 – 2005 and 2007 – 2009 as the LCF product for a
landscape level analysis of thermal response. A nested regression (site, month, and
year) was conducted between the LCF product and gridded climate product (PRISM)
and point-based meteorological station data. LCF exerted a -0.1 to -0.7 degree C per
LCF hour temperature reduction. Maps of these products show that specific thermal
response depends on adjacent landform topography and direction to prevailing winds in
addition to distance from coast. Sites closest to the coast have less thermal variability
between cloudy and cloud free days than sites further from the coast suggesting coastal
sites are more strongly influenced by ocean temperature than shortwave shading by low
clouds. The thermal relief provided by inland summertime LCF is equivalent in
magnitude to the temperature increase projected by the driest and hottest of regional
downscaled climate models and using the highest emission IPCC scenario.
Extrapolating these thermal calculations can facilitate future quantifications of the
ecosystem service provided by summertime low clouds and fog.
~*~
A multi-proxy record of paleoflood events imprinted on oxbow lake sedimentary
sequences of the Dak Bla River, Kontum, Vietnam
Trang T. Trana, Lora R. Stevensb, Thich Vua, Rane Andersonb
aVietnam
National University (trangtthb@gmail.com), bDepartment of Geological
Sciences, California State University, Long Beach (lora.stevens@csulb.edu)
The Central Highlands of Vietnam are susceptible to frequent and devastating floods.
This mountainous region is an area of intense hydroelectric development but little is
known about flood frequency or magnitude. A long-term flood history of this region, as
well as a better assessment of the relationship between extreme precipitation events
and flooding, is essential to provide natural resource managers with the necessary data
for adaptation and mitigation plans. However, river gauges only record flood events
59
spanning the last ~40 years. During this time, there have been three major floods along
the Dak Bla River (AD 1972, 1996, 2009). Each is associated with heavy rains from
tropical storms. This suggests that climatic conditions conducive to tropical storms may
result in more floods.
Two paleomeanders (Oxbows East and Southeast) of the Dak Bla River present
valuable archives for reconstructing past floods. Oxbow East is located at the eastern
edge of Kontum City and approximately 200m away from the main river. Oxbow
Southeast is about 500m away on a large point bar. Both lakes were analyzed for grain
size changes, biogenic silica concentration, carbon and nitrogen percentages, and
magnetic susceptibility (MS). Unlike temperate lakes, visual changes in sediment are
not obvious and bioturbation through rice farming may be significant. Therefore, flood
events are based on the occurrence of at least three of the following changes:
increased grain size (higher percentage of sand), high values of C/N from terrestrial
carbon debris, decreased carbon percentages, and decreased biogenic silica. During
non-flood years, these proxies will exhibit the opposite trends. While magnetic
susceptibility (MS) may be an excellent proxy for flood events in organic-rich midlatitude lakes, it is not useful in our tropical setting. MS does show peaks, but these
occur in finer sediment after the main flood event.
Based on the above model and preliminary data, Oxbow East has recorded 8 to 12
flood events over the last ~150-200 years. Oxbow Southeast has a younger record. It
has a maximum of 8 events, although at least four of these occur after AD 1950.
Unfortunately, due to radiocarbon plateaus, precise dating of individual events is not
possible.
~*~
Changes in Holocene Climate, Fire and Vegetation from the Northeastern Great
Basin: A 13,500 Year Sedimentary Record From Swan Lake, ID.
David Wahla, Lysanna Andersona, Jose Rosarioa, David M. Millera, and Liubov
Presnetsovaa
a U.S.
Geological Survey, Menlo Park CA 94025 (dwahl@usgs.gov;
landerson@usgs.gov; jrosario@usgs.gov; dmiller@usgs.gov, lpresnetsova@usgs.gov)
Precipitation patterns in the western US are characterized by a north-south dipole,
typically manifesting as wet conditions in the northwest and a dry southwest. This
pattern is, in large part, determined by the strength and position of the Pacific
subtropical jet, which is responsible for the generation and trajectory of winter storms
that provide the majority of annual moisture. Modern climate variability on
interannual/decadal timescales results in latitudinal shifts in the boundary between the
wet-north/dry-south, with strong positive ENSO/PDO events associated with drying in
the north and increased precipitation in the south. Previous paleoclimate work in the
Great Basin has suggested some coherence in the timing of major climatic shifts during
the Holocene, however past spatial variability of the dipole remains poorly understood.
Here we present new data from a site that lies within the transition zone of the
precipitation dipole. This study seeks to provide insight into the timing and magnitude of
60
late-glacial and Holocene climate variability in the northeastern Great Basin in order to
better understand past spatial variability of precipitation patterns.
In 2011, a 7.65 m sediment core was raised from Swan Lake, a small wetland located in
southeastern Idaho along the northeastern boundary of the Great Basin. Swan Lake
was formed in the spillway channel created by the catastrophic flooding of Lake
Bonneville ~18 ka BP. Pollen, charcoal, clumped isotope, macrofossil, and
sedimentological data are used to reconstruct vegetation, fire history and lake
level/groundwater flux over the last 13,500 years. Age control is provided by 15 AMS
radiocarbon determinations. Results are placed in the context of regional paleoclimate
studies and build on earlier work by Bright (1966) who reported on pollen, macrofossils
and sedimentology from Swan Lake. Our data show reductions in fire frequency
coinciding with periods of relatively dry conditions between ~12.5-6.5 and ~4.6-1.1 ka
BP. The intervening periods (~6.5-4.6 ka BP and ~1.1-0 ka BP) appear to have been
relatively wet. These preliminary data suggest that, although in the transition zone of
the precipitation dipole, the Swan Lake area has an overall climatic affinity with
southwestern U.S.
~*~
An unparalleled, ultra-resolution tree-ring dataset for climate and snow
reconstructions in the American West
Simon S.-Y. Wanga, Justin DeRoseb, Daniel Barandiarana, John Shawb
a Department
of Plants, Soils and Climate, Utah State University, Logan UT 84322
(simon.wang@usu.edu); b USDA Forest Service, Rocky Mountain Research Station,
507 25th Street Ogden, UT 84401 (rjderose@fs.fed.us)
We introduce a novel tree-ring data set, with unparalleled spatial density, for use as a
climate proxy. Ancillary Douglas-fir and pinyon pine tree-ring data collected by the U.S.
Forest Service Forest Inventory and Analysis Program (FIA data), among 7 other
species, were subjected to a series of tests to determine their feasibility as climate
proxies. First, temporal coherence between the FIA data and previously published treering chronologies was found to be significant. Second, spatial and temporal coherence
between the FIA data and water year precipitation was strong. Third, the FIA data
captured the El Niño-Southern Oscillation dipole and revealed considerable latitudinal
fluctuation over the past three centuries. Finally, the FIA data confirmed the quadraturephase coupling between wet/dry cycles and Pacific decadal variability known to exist for
the Intermountain West. We also present the first reconstruction of April 1 snow water
equivalent (SWE) for the state of Utah using densely populated increment cores
collected by the U.S. Forest Service Forest Inventory and Analysis (FIA) Program. SWE
measurements and ring width measurements were projected onto an 1/8° grid mesh
and a regression model was constructed to predict SWE for the period 1850-1995.
Results showed a statistically significant correlation with observed SWE, and broadly
captured variability of SWE observations on inter-annual to inter-decadal time scales.
These results highlight the possibility of further developing high spatial resolution
climate proxy data sets for the western U.S.
~*~
61
Fire and Ice - California drought and super cold East in a changing climate
Simon S.-Y. Wanga, Larry Hippsa, Robert Gilliesb, J.-H. Yoonc, and Boniface Fosua
a Department
of Plants, Soils and Climate, Utah State University, Logan UT 84322
(simon.wang@usu.edu); b Utah Climate Center, Utah State University, Logan, UT 84322
(Robert.Gillies@usu.edu); c Pacific Northwest National Laboratory, Richland, WA (jinHo.Yoon@pnnl.gov)
The ongoing California drought was initiated by an anomalous high-amplitude ridge
system in the winter of 2013–2014. The anomalous ridge was investigated using
reanalysis data and the Community Earth System Model (CESM). It was found that the
ridge emerged from continual sources of Rossby wave energy in the western North
Pacific starting in late summer and subsequently intensified into winter. The ridge
generated a surge of wave energy downwind and deepened further the trough over the
northeast U.S., forming a dipole. The dipole and associated circulation pattern is not
linked directly with either El Niño–Southern Oscillation (ENSO) or Pacific Decadal
Oscillation; instead, it is correlated with a type of ENSO precursor. Multi-model analysis
using CMIP5 model outputs indicated that the connection between the dipole and
ENSO precursor has become stronger since the 1970s, and this is attributed to
increased greenhouse gas loading as simulated by the CESM. Therefore, there is a
traceable anthropogenic warming footprint in the enormous intensity of the anomalous
ridge during winter 2013–2014 and the associated drought. When projecting for the
future, the large-member ensemble simulations of CESM indicated increases in fire
counts and extreme drought occurrences, both of which are increasingly linked to the
ENSO cycle.
Furthermore, the extent to which climate oscillations will modulate wildfire occurrences
in the changing climate is examined. The consensus of climate model has projected a
generally wetter climate for California towards the latter part of the 21st century, a
scenario that seems to counter the projections of more fires in a wetter climate. Using
CESM that directly outputted fire parameters, it is found that both the mean fire
probability and annual precipitation in California are projected to increase slightly
towards the end of the 21st century. However, the fluctuation in annual precipitation will
amplify leading to a robust increase in the variation of vegetation and fire probability.
The increased fluctuation of fire probability is associated with the amplified ENSO cycle
at the 4-5 year frequency. This association suggests a potential for increasingly severe
wildfires to occur more regularly in the future.
~*~
Paleoenvironmental Reconstruction Using Elemental Analysis
Danielle M. Ward
Department of Geography, University of Utah, Salt Lake City, UT 84112
(danielleward026@gmail.com)
Range Creek Canyon, located on the Colorado Plateau, is an area of interest due to
habitation by ancient Fremont people for hundreds of years. Range Creek Canyon is
62
one of the most well preserved areas of Fremont habitation, with multiple undisturbed
archaeological sites. The causes behind their disappearance from Range Creek
Canyon remain a mystery, but there is a possibility that it is climate related, such as
from an extended period of drought. By reconstructing the environment in which the
Fremont people lived, the potential reasons for their departure can become clearer.
Using a handheld XRF scanner, a five meter bog core from Range Creek Canyon was
examined for its elemental composition. Elemental analysis is a useful method of
environmental reconstruction because many elements such as Ti, Fe, and Rb will
fluctuate with changes in the weathering regime or atmospheric deposition of an area,
therefore leading to increased understanding to the causes behind these changes. The
variation in element distribution throughout the Range Creek Canyon seem to be linked
to the weathering of clay minerals, which could indicate that the elemental analysis
could be a good proxy for precipitation in this area.
~*~
Water supply and landscape droughts: historical and projected hydrology of the
Great Basin.
Stuart B. Weissa, Alan.L. Flintb, and Lorrie.E. Flintb
a Creekside
Center for Earth Observation, 27 Bisho Lane, Menlo Park, CA 94025
stu@creeksidescience.com, b US Geological Survey, California Water Science Center,
6000 J St., Sacramento, CA 95819, Emails: aflint@usgs.gov; lflint@usgs.gov
Impacts of climate change in Southwestern North America will manifest through
changes in the hydrologic cycle. Downscaled climate data and projections run through
the Basin Characterization Model (BCM) produce time series of hydrologic response –
recharge, runoff, actual evapotranspiration (AET), and climatic water deficit (CWD) that directly affect water resources and vegetation. More than 50 climate projections
from CMIP5 were screened using a cluster analysis of end-century (2077-2099)
seasonal precipitation and annual temperature for 4 regions – California, Great Basin,
Lower Colorado, and Upper Colorado – to produce a reduced subset of 12 that cover a
range of macroclimate response. Importantly, variations among GCMs in summer
precipitation produced by the SW monsoon are captured. Droughts can be classified
into water supply (low runoff and recharge) and landscape (increased CWD) droughts
that do not always coincide. Analysis of HUC8s in the Great Basin shows multi-year
water supply droughts in the late 1950s, late 1970s, early 1990s, and 2010s. The early
1990s stand out as the exceptional multi-year CWD drought, especially in the eastern
Great Basin. Monsoonal moisture ameliorates annual CWD. Multiple projected time
series for HUC8 watersheds are compared with these historical extremes, and the
decadal time frames of exceedances are characterized. This approach provides a
platform for vulnerability and risk analyses at fine spatial scales.
~*~
63
Look to the past to understand future conifer responses in the Greater
Yellowstone Ecosystem
Cathy Whitlocka, Virginia Iglesiasb, and Teresa Krausec
aMontana
Institute on Ecosystems and Dept of Earth Sciences, Montana State
University, Bozeman MT 59717 (whitlock@montana.edu); bLaboratoire ChronoEnvironement, Université de Franche-Comté, 16 Route de Gray, 2500 Besançon,
France (virginia.iglesias@mshe.univ-fcomte.fr); cUS Geological Survey Southwest
Climate Science Center, 1955 E 6th St, Tucson AZ 85719 (tkrause@usgs.gov)
Climate-change projections in the western United States include rising temperatures,
decreased winter snowpack, and increased moisture deficits in the coming decades.
Whitebark pine (Pinus albicaulis) is a keystone species in subalpine environments, and
one that is highly vulnerable to projected climate trends. In the past two decades,
whitebark pine populations have experienced a dramatic decline as a result of mountain
pine beetle infestation, blister rust, high-severity fires, and drought. A common approach
for inferring future whitebark pine distributions uses species-niche modeling, which is
based on the relation between current occurrence and present-day bioclimatic
parameters. While these models capture the realized niche at present, an examination
of the paleoecological record suggests that the fundamental (or full) niche space is likely
much larger and encompasses a wider range of climate variability. To assess a broader
array of bioclimatic conditions for GYE conifers, we examined the fossil record and
particularly species responses to past changes in climate, fire activity and interspecific
competition. General additive modeling of pollen/charcoal data from 11 sites across the
GYE indicate that white pines reached maximum population size and distribution
~12,000 -7500 years ago and declined thereafter. Population dynamics tracked
variations in summer insolation, such that white pines were most abundant when
summer temperatures, winter snowpack and fire frequency were higher than present.
Competition from lodgepole pine after ~7000 years ago likely limited limber pine at low
elevations and whitebark pine at high elevations. Paleoecological data indicate that
white pines have been surprisingly resilient to high summer temperature, summer
drought, and fire activity. Conversely, winter conditions and biotic interactions, which are
rarely included in simulations, have been critical limiting variables for high-elevation
conifers in the past and will likely be so in the future. Appropriate strategies for species
conservation and ecosystem management should be based on a longer historical
baseline than that provided by recent observations and consider biotic factors that may
complicate species-climate interactions.
~*~
Urbanization as a likely driver of reduced summer fog and increased drought in
coastal southern California
A. Park Williamsa*, Rachel E. Schwartzb, Sam Iacobellisb, Richard Seagera, Benjamin I.
Cookc, Christopher J. Stilld, Gregory Husake, and Joel Michaelsene
a
Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964
(*williams@ldeo.columbia.edu); b Scripps Institution of Oceanography, University of
64
California, San Diego, La Jolla, CA 92093; c NASA Goddard Institute for space Studies,
New York, NY 10025; d Forest Ecosystems and Society, Oregon State University,
Corvallis, OR 97331; e Geography Department, University of California, Santa Barbara,
Santa Barbara, CA, 93106
Subtropical marine stratus clouds regulate climate globally and also mitigate drought in
coastal regions. On the west coast of North America, stratus clouds are most common
during the rainless summer. Drought mitigation occurs via daytime shading and
nighttime water deposition from fog. Despite global and local importance of subtropical
stratus clouds, future trends and causes of past trends are not well understood. We
used hourly records of cloud-base height from 24 airfields in coastal southern California
(CSCA) to diagnose the causes of interannual variations and multi-decade trends in
summer stratus cloudiness since the mid-1900s. Interannual variations in summer
stratus-cloud frequency are spatially coherent throughout the region, indicating a
common set of climatological controls across the region. The most important factors
promoting cloudy years are atmospheric stability above the marine boundary layer
(MBL), a deep MBL, and a low altitude of condensation, caused by a low dew-point
depression near the surface. Although interannual variability of stratus frequency was
spatially consistent, trends were spatially variable, particularly for night and early
morning stratus clouds. Most airfields experienced declines in stratus frequency,
corresponding with rising stratus-cloud base heights and decreasing fog frequency.
Among airfields, trends in stratus-cloud base height and fog frequency were significantly
related to nighttime warming rates, where warming corresponded to rising cloud-base
height and declining fog frequency. Differences in nighttime warming, but not daytime
warming, were strongly and positively related to nearby fraction of urban cover,
consistent with a classic urban heat island effect. Warming increases the near-surface
dew-point depression, causing clouds to develop higher in the MBL and less often.
Continued urban warming, rising summer cloud-base heights, and declining stratuscloud frequency are likely to positively feed back on one another, leading to drought
effects that profoundly impact ecological and human systems in CSCA.
~*~
The role of anomalous ridging in U.S. West Coast-wide drought over multiple
centuries
Erika K. Wisea
a Department
of Geography, University of North Carolina at Chapel Hill, Chapel Hill, NC
27599 (ekwise@email.unc.edu)
Drought in the western U.S. over the instrumental period has frequently been
characterized by a north-south wet/dry pattern differentiating central and southern
California from northern California, Oregon, and Washington. The recent California
drought, which extended to cover the entire West Coast of the U.S. by the winter of
2013-2014, is a strong reminder that this is not always the case. It has been
hypothesized that the strong high-pressure ridge associated with the 2013-2014 drought
was associated with anthropogenic climate change, based on instrumental data and
modeling. In this study, existing tree ring-based reconstructions of Palmer Drought
65
Severity Index and geopotential height are combined with new, spatial reconstructions
of cool-season Standardized Precipitation Index and Standardized Precipitation
Evapotranspiration Index to examine the occurrence of West Coast-wide drought over
the past several centuries and the associated atmospheric circulation patterns. Results
indicate that the persistent, elongated high pressure ridge characteristic of the 19761977 and 2013-2014 severe droughts has been a recurrent feature associated with
these relatively rare drought patterns over the pre-instrumental period. Results of this
study also emphasize distinctions between targeted reconstruction season and drought
measure.
~*~
Investigating the role of temperature in mediating relationships between cool
season precipitation and water year streamflow in the Upper Colorado River
basin
Connie A. Woodhousea, Gregory T. Pedersonb, Kiyomi Morinoc, and Gregory McCabed
aSchool
of Geography and Development, University of Arizona, Tucson, AZ 85721
(conniew1@email.arizona.edu); bU.S. Geological Survey, 2327 University Way (Suite
2), Bozeman, MT 59715 (gpederson@usgs.gov); cLaboratory of Tree-ring Research,
University of Arizona, Tucson, AZ 85721 (kiyomi@email.arizona.edu); dU.S. Geological
Survey, Denver Federal Center, MS 412, Denver, CO 80225 (gmccabe@usgs.gov)
Upper Colorado River basin water year streamflow, and consequently drought, is driven
largely by cool season precipitation, with October to April total precipitation explaining
about two-thirds of the variability in estimated natural flows at Lees Ferry. Because of
this relationship, when cool season precipitation is low, water year streamflow is
correspondingly low, and vice versa. In a subset of years, these two variables are less
closely linked, with water year flows greater or less than expected given the cool season
precipitation. In these years, temperature appears to be playing a bigger role. Over the
years 1906-2010, spring and early summer temperatures account for about eight
percent of the variability in water year flow, but they explain 45% of the variance in the
30 years with the largest difference between percentile values of water year flow and
cool season precipitation. Of the 30 years, flow is less than might be expected given
the cool season precipitation in 16 years, and greater than expected given the
precipitation in 14 years. Both sets contain above and below median flow years.
Average spring/summer temperatures are cooler in both high and low flow years that
show flows higher relative to cool season precipitation. Conversely, average
temperatures are quite warm (in the 80th percentile) in years when flow is below the
median and less than might be anticipated from precipitation. The distribution of the 30
years shows clusters of the different types of years. For example, above median flows
years with higher than expected flow given precipitation are mostly found in the period
from 1918-1930, although this set also includes the very high flow years of 1983 and
1983. Below median years with flows less than would be expected from precipitation
amounts occur mostly after 1988. The role of antecedent soil moisture was also
investigated, and results suggest wet antecedent conditions may be most important in
66
the Green River basin part of the upper Colorado River basin, in above median flow
years, with flows higher than anticipated from cool season precipitation.
~*~
Hint of an Expanded Summer Monsoon during the Mid-Holocene Climatic
Optimum in the Southern Owens Valley Region, California
Wallace B Woolfenden
USDA Forest Service (ret.), 120 Wilson Road, Swall Meadows, CA 93514
(paleotoon@gmail.com)
A minimally dated mid- to late Holocene pollen sequence from a core retrieved in 1963
on the northwest side of Owens Lake by Paul S. Martin and David Adam shows
relatively high pine and fir pollen percentages from ~6000 to 4500 BP. The interpolated
age range correlates with curves from marine cores of a species of foraminifera
(Globigerinoides sacculifer) that tracks the northern progression of the ITCZ and
expansion of the southwest monsoon. Owens Lake had almost desiccated then.
Apparently an expanded monsoon provided sufficient water availability in the summer
and fall for montane conifer recruitment and growth during higher temperatures and
lower winter precipitation of the Mid-Holocene Climatic Optimum when lower elevations,
including Owens Valley, were arid. Packrat midden and archaeological evidence in the
northern Inyo Mountains indicates a human prehistoric land use response to increased
occupation of pinyon woodland at that time.
~*~
Precise timing and duration of the late Holocene pluvial-arid sequence at Mono
Lake, CA.
Susan R. H. Zimmermana, Sidney R. Hemmingb, and Scott W. Starrattc
aCenter
for Accelerator Mass Spectrometry, Lawrence Livermore National Lab,
Livermore CA 94550 (zimmerman17@llnl.gov); bDept. of Earth and Environmental
Science, Columbia Univ., and Lamont-Doherty Earth Observatory, Palisades, NY 10964
(Sidney@ldeo.columbia.edu); cVolcano Science Center, US Geological Survey, Menlo
Park, CA 94025 (sstarrat@usgs.gov)
Stine (1990, PPP) produced a sub-centennial-scale, well-dated, absolute lake level
curve for the last 2000 years in the Mono Basin, constructed from outcrops, shoreline
pits, and other landforms. That record gave an early indication of the late Holocene
pluvial-arid sequence between 4000 and 2000 yrs BP, which has now been found in
lake records across the region. The pluvial timing comes from a single 14C age from a
deltaic transgressive sequence, which yields a 2-sigma calibrated age range of 3560 –
3990 cal yr BP, and the end of the arid period is constrained to be before ~1600 cal yr
BP. The timing of the initiation of the pluvial, and its duration, and the timing of the
subsequent decay into aridity are recorded by the BINGO-4A-1N core, recovered from
~3 m water depth in 2010. Although this core is in the western embayment and
potentially subject to non-climatic deepening due to down-dropping on the Sierran
67
frontal fault, the short duration of the record and the broad match to the Stine record
give us confidence in the interpretation of changes.
In BINGO-4A-1N, deeper lake intervals are recorded by finely laminated, carbonatepoor muddy silt, while arid conditions are characterized by high concentrations of
coarse biogenic carbonate, such as Newton (1994, SEPM Sp. Pub. 50) mapped in very
shallow waters in the modern lake. A significant drop in carbonate occurring 7 cm above
a 14C date of 4340 ± 95 cal yr BP initiates an interval of low-carbonate, black and green
silt with cm-scale bedding, corresponding to the pluvial period. The subsequent 11 cm
interval of mm-scale laminations ends abruptly in coarsely bedded carbonate-rich
sediments, marked by the highest Ca/Ti values in the core. The end of the late
Holocene arid period is dated by two 14C dates of 2070 cal yr BP, with ~200 yr
uncertainty. The late Holocene pluvial period in the BINGO core therefore dates to
~4300 to 3350 cal yr BP, and the ensuing drought to 3350 to 2070 cal BP.
~*~
68
NOTES
69
HTTP://XKCD.COM/1410/
XKCD.com Randall Munroe