Abstracts from AGU2006
TALKS
Wednesday 0800h
Global Change and Mountain Climate I: Gradients, Resources, and Ecosystems
Presiding: D Cayan, Scripps Institution of Oceanography; C Millar, USDA Forest
Service
C31C-01
As the West Warms: Watching Our Home Burn
* Diaz, H F (henry.f.diaz@noaa.gov) , NOAA ESRL, 325 Broadway, Boulder, CO
80305, United States
Mountain environments have been shown to be particularly sensitive to changes in
climate because they are places with sharp vertical gradients, which result in the stacking
of natural ecotones with elevation. The impact of global climate change in mountainous
regions may lead to rapid and irreversible changes in a number of areas; these range from
major changes in the seasonal hydrographs of meltwater-driven streams affecting
communities that depend on the melting of frozen precipitation for their water supplies,
to increases in large and intense forest fires, arising from a combination of factors that
include increasing temperature and insect outbreaks, to changes in growing seasons and
species extinction. In the last 10 years, rising temperatures occurring during a period of
diminished precipitation in the western United States has led to unprecedented drought
conditions�the most widespread severe drought in the period of instrumental records.
An examination of the available climate record suggests that the US, and in particular the
West, may be entering, or perhaps is in the midst of a period of rapid warming. The
combination of much warmer than normal temperature, likely driven by global warming,
and a drier than normal period, regardless of its cause, may result in more frequent and
widespread western droughts, with all its attendant consequences of enhanced wildfire
risk, water supply problems, and a host of other environmental threats. Results from
recent climate model simulations underscores the potential threat to the western United
States resulting from greenhouse-gas-induced global warming. I will examine the latest
set of climate records from both the North and South American Cordillera, highlighting
some impacts already evident in many areas. Although some political action has been
taken to address the issue of global warming impacts on western society, the actions to
date have been largely in the nature of calls to mitigate some of the expected impacts.
C31C-02
Snowcover Along Elevation Gradients in the Upper Merced River Basin of the Sierra
Nevada of California from MODIS and Blended Ground Data
* Bales, R (rbales@ucmerced.edu) , University of California, Merced, PO Box 2039,
Merced, CA 95344, United States
Rice, R (rrice@ucmerced.edu) , University of California, Merced, PO Box 2039, Merced,
CA 95344, United States
Accurate, frequent satellite-derived snow covered area (SCA) products provide the
opportunity to explore the spatial patterns of snow, as well as the impact of snow
accumulation and ablation on snow distribution along elevation gradients. Blending a
MODIS fractional snow cover product with interpolated point snow water equivalent
(SWE) measurements and energy balance calculations yields composite maps of the
spatial distribution of SWE. Results from the 2004 and 2005 water years show the utility
of the MODIS fractional SCA product to estimate snow accumulation and melt along
300-meter elevation gradients in the 1,755 km2 Upper Merced River Basin of the Sierra
Nevada of California. The analysis considers the elevation bands from 1,500 to 3,900 m
with 40% of the elevation between 2,100-2,700 m, while the 1,500 m elevation band is
considered the transitional rain/snow zone. Spatial maps of SWE highlight elevational
bands that contribute significantly to snowmelt across the basin, as well as those
elevational bands that are susceptible to warming and thus rapid depletion of the
snowcover. The results of the 2004 ablation season demonstrate the implications along
the elevation gradients of an above normal mid-season snowcover of 120% impacted by
an unseasonable warm and dry air mass that rapidly depleted the snowcover across all
elevation gradients, leading to a below average snowpack of 84% by April 1. However,
the 2004 SCA and composite SWE maps shows the compression of the SCA and SWE
along elevation zones when compared to the 2005 snow products when the April 1
snowpack was 160% of normal. These results highlight the critical elevation zones in
which the snowpack is susceptible to climate variations, while underscoring deficiencies
in the current measurement network which provide the impetus for designing of an
adequate measurement network along elevational gradients.
C31C-03 INVITED
Hydrology and Climate in the Sierra Nevada: Disproving the Myth of Linear Gradients
with Elevation
* Lundquist, J D (jdlund@u.washington.edu) , University of Washington Civil and
Environmental Engineering, Wilcox 165, Box 352700, Seattle, WA 98195-2700, United
States
Cayan, D R (dcayan@ucsd.edu) , Scripps Institution of Oceanography United States
Geological Survey, 9500 Gilman Dr., La Jolla, CA 92093-0224, United States
Dettinger, M D (mdettinger@ucsd.edu) , Scripps Institution of Oceanography United
States Geological Survey, 9500 Gilman Dr., La Jolla, CA 92093-0224, United States
Linear lapse rates have traditionally been used to model variations in atmospheric
variables with elevation, including temperature, precipitation, humidity, and solar
radiation. For example, in the standard atmosphere, temperatures decrease at a rate of
6.5$^{\circ}$C km$^{-1}$, and this lapse rate has traditionally been used to model
snowmelt, to estimate the elevation where falling snow changes to rainfall, and to
estimate mountain temperatures in the distant past or in future climate simulations.
However, a network of over 100 self-recording stream and temperature sensors, deployed
in or near Yosemite National Park, California since summer 2001, combined with a
transect of full meteorological stations, have demonstrated that the assumption of
linearity with elevation is often violated. In complex topography, winds control where air
rises and descends, aspect and shading create large variations in solar radiation, and flatbottomed valleys pond cold-air lenses at night. This paper uses 5 years of air temperature,
stream stage, solar radiation, and precipitation observations at elevations traversing the
Sierra Nevada to demonstrate the power of these local effects and how they are
modulated by large-scale weather patterns. For example, during some years, spring snow
melt progresses from low to high elevations in an orderly fashion, while in other years,
spring melt occurs almost simultaneously over all elevations from 1800 to 3000 m. These
results emphasize the need for spatially and temporally comprehensive observations of
key variables and processes in mountain catchments and are an important consideration
when thinking about how higher elevations in different topographic settings may respond
to climatic changes.
C31C-04
Abiotic Gradients and Climate-Growth Relationships in Douglas-fir: Water Limits Tree
Growth in Mountain Ecosystems from Stand to Region
* Littell, J S (jlittell@u.washington.edu) , University of Washington Climate Impacts
Group, Box 354235, Seattle, WA 98195-4235, United States
* Littell, J S (jlittell@u.washington.edu) , University of Washington College of Forest
Resources, Box 352100, Seattle, WA 98195-2100, United States
Peterson, D L (peterson@fs.fed.us) , USDA Forest Service Pacific Northwest Research
Station, Pacific Wildland Fire Sciences Lab, 400 N. 34th St.,Suite 201, Seattle, WA
98103, United States
McKenzie, D (donaldmckenzie@fs.fed.us) , USDA Forest Service Pacific Northwest
Research Station, Pacific Wildland Fire Sciences Lab, 400 N. 34th St.,Suite 201, Seattle,
WA 98103, United States
Elevation is often used as sampling gradient because it integrates factors influencing
climate-mediated biophysical processes. However, in terms of mechanistic attribution of
cause and effect in mountain ecosystems, elevation is essentially qualitative because it is
a surrogate for the water and energy variables that affect ecological response. In this
study, we develop a gradient sampling strategy that considers continentality,
physiography, and topography as non-climatic factors that could influence the
relationship between tree-growth and regional climate. We developed a network of 124
Douglas-fir (Pseudotsuga menziesii) tree-ring chronologies from the western Olympic
Peninsula in Washington to the eastern Rocky Mountain Front in Montana. Growthclimate correlations across the sampled gradients consider two different scales of climate
variables as potential controlling factors on tree growth. Gradients of sensitivity to
growth limiting climate variables emerged: most plots were significantly limited by water
supply, while a few were limited by low temperature and/or snowpack. The sampled
Douglas-fir population's sensitivity to summer water balance deficit indicates that
increases in April to September temperature without increases in summer precipitation or
soil moisture reserves are likely to cause decreases in growth over much of the sampled
area, especially east of the Cascade crest. In contrast, Douglas- fir at some higher
elevation sites where seasonal photosynthesis is currently limited by growing season
length or low growing season temperature may exhibit increases in growth. By focusing
less on elevation gradients and more on a complete set of biophysical variables, we were
able to quantify the growth-climate relationships across a substantial fraction of the
species niche in terms of limiting climatic factors.
C31C-05 INVITED
140-Year Dynamics of a Forest Ecotone Under Climate and Environmental Change
* Thorne, J H (jhthorne@ucdavis.edu) , University of California, Dept Environmental
Science 2132 Wickson Hall 1 Shields Ave, Davis, CA 95616, United States
Kelsey, R (trkelsey@ucdavis.edu) , University of California, Dept Environmental
Science 2132 Wickson Hall 1 Shields Ave, Davis, CA 95616, United States
Terrestrial plant species live within elevational limits. Response to climate change at the
lower edge of a species' range can be quite different from response at its upper limits.
Lower edge dynamics can sometimes lead to rapid shifts, if establishment conditions
have changed. Under those circumstances, stand replacing disturbances can cause the
local extirpation of the species because subsequent recruitment is ineffectual. We
examined the position of lower edge of Pinus ponderosa forests in El Dorado County,
California, where the tree occupies a broad elevational gradient. We found that over 140
years, this forest had shifted upslope over 500 meters. Minimum monthly air
temperatures from stations forming an elevational transect in these mountains have
warmed over the past 60 years by over 30 C. In the zone of the shift, this means that now
no months are frozen, whereas 60 years ago December, January and February were below
00C. This warming is associated with advancing summer drought conditions, which set
the stage for drought stress and reduced competitive abilities in the seedlings. We present
an estimate for how much sooner summer drought conditions begin. Potential
confounding factors: including grazing, agriculture, fires and urban expansion were found
to occupy only 40% of the 540 km2 of forests lost since 1850 in the County. Forest
change here is a disturbance initiated, recruitment limited system. Implications of this
research include that the lower edge of coniferous systems are sensitive to climate
change, via a combination of direct and indirect effects. A possible feedback between this
edge and the lower limits of the snowline is discussed.
C31C-06
25 Years of Variability in the Biology of Salix-feeding Beetles and Associated Insects
Along a Sierra Nevada Elevation Gradient, California: Are There Long-term Trends?
* Smiley, J T (jsmiley@wmrs.edu) , University of California White Mountain Research
Station, 3000 E. Line St., Bishop, CA 93514
Rank, N E (rank@sonoma.edu) , Department of Biology Sonoma State University, 1801
E. Cotati, Rohnert Park, CA 94928
Dahlhoff, E (edahlhoff@scu.edu) , Department of Biology Santa Clara University, 500 El
Camino Real, Santa Clara, CA 95053
We have been studying the ecology, evolution and physiology of the willow leaf beetle,
Chrysomela aeneicollis, in the Eastern Sierra Nevada Mountains, California, since the
early 1980's. One principal focus of this long-term study has been analysis of elevation
gradient effects to the food web which includes willows (Salix ssp.), C. aeneicollis, and
several predators including the hover fly Parasyphus melanderi and the hole-nesting wasp
Symmorphus cristatus. We have observed and documented asymmetries along the
elevation gradient. At upper elevations, populations confront higher frequencies of
lethally cold nighttime temperatures and intensity of storms. When individuals are
transplanted among elevations, upper elevation populations grow faster and survive better
at upper elevation sites than populations from lower elevations. Our observations suggest
that dispersal is sufficiently restricted among elevations to allow genetic differences in
ability to respond to stressful climate to emerge. Lower elevation populations are subject
to a wider range of predatory insect species, and predation plays a relatively larger role in
their reproductive success. We have documented upward shifts in range for some
populations of about 300 meters over the 25-year period of the study, although other
populations do not show such shifts. We are preparing to document further range shifts
along the elevation gradients by monitoring habitats which are currently at or above the
upper range limits of the plants, beetles and predators, and looking for recruitment of new
populations at those sites.
C31C-07 INVITED
The Grinnell Project; Small Mammal Responses to Climate in California
* Conroy, C C (ondatra@berkeley.edu) , Museum of Vertebrate Zoology, 3101 Valley
Life Sciences Building, University of California, Berkeley, CA 94720, United States
Koo, M (mkoo@berkeley.edu) , Museum of Vertebrate Zoology, 3101 Valley Life
Sciences Building, University of California, Berkeley, CA 94720, United States
Monahan, B , Museum of Vertebrate Zoology, 3101 Valley Life Sciences Building,
University of California, Berkeley, CA 94720, United States
Parra, J , Museum of Vertebrate Zoology, 3101 Valley Life Sciences Building, University
of California, Berkeley, CA 94720, United States
Moritz, C , Museum of Vertebrate Zoology, 3101 Valley Life Sciences Building,
University of California, Berkeley, CA 94720, United States
Between 1915 and 1920, Joseph Grinnell and colleagues investigated the diversity of
mammals, reptiles, amphibians and birds across what they termed the Yosemite Transect,
an area spanning portions of the San Joaquin Valley, the Sierra Nevada, including about
1/3 of Yosemite National Park, and ending at Mono Lake. Their data collection included
preservation of series of specimens at a large number of locations, point counts of birds,
photography and extensive natural history notes, all of which are still archived at the
Museum of Vertebrate Zoology at UC Berkeley. Beginning in 2003, researchers from the
MVZ began retracing this work, collecting specimens, using point counts, and retaking
some photographs. The comparison of the two periods indicates that some mammals have
shifted their ranges greatly. Most taxa show an elevation increase, either an increase at
the top for middle elevation species, or a retraction at the bottom for higher elevation
species. However, not all species moved, and one high elevation species moved down. To
further investigate how changes observed in Yosemite might also apply to larger spatial
scales, our group has been using historic climate surfaces, historic specimen localities,
and a variety of modeling methods to predict statewide changes in species' distributions.
Other potential sites to be revisited include the Lassen Transect in Northern California,
the Colorado River, and the San Bernardino Mountains.
http://mvz.berkeley.edu/Grinnell/index.html
C31C-08
Vertical gradients of PCBs and PBDEs in fish from European high mountain lakes
* Grimalt, J O (jgoqam@cid.csic.es) , Department of Environmental Chemistry (IIQABCSIC), Jordi Girona, 18, Barcelona, 08034 Spain
Gallego, E (egpqam@iiqab.csic.es) , Department of Environmental Chemistry (IIQABCSIC), Jordi Girona, 18, Barcelona, 08034 Spain
Bartrons, M (mbvqam@cid.csic.es) , Department of Environmental Chemistry (IIQABCSIC), Jordi Girona, 18, Barcelona, 08034 Spain
Catalan, J (catalan@ceab.csic.es) , Limnology Unit (CSIC-UB). Centre for Advanced
Studies of Blanes (CEAB-CSIC), Acc�'ƒÂ©s Cala St. Francesc, 14,
Blanes, 17300 Spain
Camarero, L (camarero@ceab.csic.es) , Limnology Unit (CSIC-UB). Centre for
Advanced Studies of Blanes (CEAB-CSIC), Acc�'ƒÂ©s Cala St.
Francesc, 14, Blanes, 17300 Spain
Stuchlik, E (evzen@blatna.cuni.cz) , Department of Hydrology, Charles University,
Vinicn�'ƒÂ¡ 7, Prague, 12044 Czech Republic
Battarbee, R (rbattarb@geog.ucl.ac.uk) , Environmental Change Research Centre.
University College London, 26, Bedford Way, London, WC1H 0AP United Kingdom
A first case of temperature-dependent distribution of polybromodiphenyl eters (PBDEs)
in remote areas is shown. Analysis of these compounds in fish from Pyrenean lakes
distributed along an altitudinal transect shows higher concentrations at lower
temperatures, as predicted in the global distillation model. Conversely, no temperaturedependent distribution is observed in a similar transect in the Tatra mountains (Central
Europe) nor in fish from high mountain lakes distributed throughout Europe. The fish
concentrations of polychlorobiphenyls (PCBs) examined for comparison showed
significant temperature correlations in all these studied lakes. In the interval of feasible
temperatures for high mountain lakes, cold trapping of both PCBs and PBDEs concerned
the less volatile congeners. In the Pyrenean lake transect the concentrations of PCBs and
PBDEs in fish were correlated despite the distinct use of these compounds and their 40
year time-lag of emissions to the environment. Thus, temperature effects have overcome
these anthropogenic differences constituting at present the main process determining their
distributions. The cases of distinct PBDE and PCB behavior in high mountains can
therefore be interpreted to reflect early stages in the environmental distribution of the
former compounds.
Authors (2006), Title, Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract xxxxx-xx
POSTERS
Wednesday 1340h
Global Change and Mountain Climate III: Gradients, Resources, and Ecosystems Posters
Presiding: M Dettinger, U.S. Geological Survey; J Lundquist, University of Washington
C33C-1276
Elevation Gradients and Climatic Consequences
* Redmond, K T (kelly.redmond@dri.edu) , Western Regional Climate Ctr, Desert
Research Institute 2215 Raggio Parkway, Reno, NV 89512-1095, United States
Steep topography usually results in gradients in surface meteorological elements.
Sometimes these gradients are extremely sharp. Frequent or persistent gradients are
expressed in climatic statistics as well. Most commonly, higher elevations are wetter and
cooler than lower elevations. The magnitude of these climate gradients vary both
spatially and temporally, generally on smaller scales for the former and on a greater
variety of scales for the latter. Orographic contributions to precipitation vary on hourly to
annual scales, and temperature inversions of different durations can alter or reverse the
vertical temperature lapse rate normally found in the atmosphere. The presence of these
factors affects the probability distributions of climate elements as a function of elevation.
This leads in turn to consequences for ecology, resource management, and data.
Orographic enhancement of Sierra precipitation varies by a factor of about three on
seasonal time scales, and more on shorter scales. Particularly strong gradients in
temperature climate are observed along the California coast, resulting in large changes in
long-term climatological probability distributions over quite short distances in elevation.
These have significant implications for plant life. For specific noteworthy events, such as
the California heat wave of July 2006, striking differences were seen over a horizontal
distance of merely 2-3 km along the Big Sur Coast, related entirely to elevation. There is
evidence of differential warming with elevation between California's Central Valley and
the Sierra Nevada. As a practical matter, the three-dimensional correlation fields of
weather and climate elements in topographically diverse regions, on differing time scales,
have complex structure, but also have certain regularities. This makes quality control of
weather and climate data sets in highly diverse topography much more challenging.
Quality control decisions that do not properly take this correlation structure (which varies
in time) into account can result in degraded data sets, a variety of Type I and Type II
errors, and paradoxically, hinder or prevent the discovery and description of the effects of
climate gradients by incorrectly altering the data sets needed to uncover and quantify the
relationships.
C33C-1277
Elevational gradients as indicators of hydrologic change
* Mote, P W (philip@atmos.washington.edu) , JISAO Climate Impacts Group, Box
354235 University of Washington, Seattle, WA 98195-4235, United States
Hamlet, A F (hamleaf@u.washington.edu) , JISAO Climate Impacts Group, Box 354235
University of Washington, Seattle, WA 98195-4235, United States
Hamlet, A F (hamleaf@u.washington.edu) , Department of Civil and Environmental
Engineering, Box 352700 University of Washington, Seattle, WA 98195-2700, United
States
Owing to strong controls on mean temperature, elevational gradients in mountainous
regions play a large role in determining many important features including quantity and
duration of snow cover and dominant vegetation. Observations and hydrological
modeling (using the Variable Infiltration Capacity, VIC, hydrologic model) are combined
to examine past changes in snow, streamflow, flood risk, and evaporation in the Western
US. Temperature plays an important role and for many of these hydrological indicators
the largest relative change occurs near the altitude of the 0$\deg$C isotherm for point
values, or in basins with a mean temperature near 0$\deg$C. In fact, temperature is a
more useful indicator than elevation, since it provides a consistent reference surface
across a wide range of latitudes. Experiments with the VIC model indicate that
temperature variability alone can explain most of the hydrologic trends, whereas
precipitation variability alone cannot. Implications for a warming world will be
discussed.
C33C-1278
Elevational Gradients of Temperature and Atmospheric Moisture on Kilimanjaro,
Tanzania
Losleben, M V (Mark.Losleben@Colorado.Edu) , Univeristy of Colorado, 818 County
Road 116, Nederland, CO 80466, United States
Hardy, D R (dhardy@geo.umass.edu) , University of Massachusetts, Dept. of
Geosciences, Amherst, MA 01003, United States
Duane, W (bill_duane@yahoo.co.uk) , University Brunei, Gadong, Negara Brunei, Dar
BE 1410 Brunei Darussalam
* Pepin, N (nicholas.pepin@port.ac.uk) , University of Portsmouth, Dept. of Geography,
Portsmouth, PO1 3HE United Kingdom
Kilimanjaro is the highest free-standing peak in Africa, rising from ~1000 to 5895 meters
above sea level, covering at least six ecological zones, and providing an excellent
platform for an elevational transect of meteorological measurements. Ten temperature
and relative humidity sensors, from 1800 m to 5800 m, show a variety of elevational
responses over their first 16 months of operation. In the zone between 3000 and 3500
meters, temperature variability is at maximum, lapse rates are lowest, and the relationship
between temperature and relative humidity changes. Ascending from the bottom,
variance increases to this zone, then decreases to the summit. This zone might be
considered one of maximum sensitivity to climate change, and thus a zone to more
carefully observe in the future. At the summit, where dry, free air conditions
predominate, glaciers are rapidly losing mass. Our data suggest that lower elevations may
be the moisture source for the summit. Typically, temperature and relative humidity are
inversely related, but our sensor data show that the reverse is true at upper Kilimanjaro
elevations, consistent with the hypothesis that diurnal upslope air flow delivers moisture
to the summit. Thus, reduction in available moisture from lower elevations through
changes in land-use, increasing pollution-related aerosols (with negative effects on
precipitation efficiency), and/or weaker upslope flow, could all be contributing to the
disappearance of the Kilimanjaro glaciers.
C33C-1279
Observed Changes in Elevational Temperature Gradients in the 20th Century.
* Pepin, N C (nicholas.pepin@port.ac.uk) , University of Portsmouth, Department of
Geography, Buckingham Building, Lion Terrace,, Portsmouth, PO1 3HE United
Kingdom
Duane, B (bill_duane@yahoo.co.uk) , University of Brunei Darussalam, Department of
Geography, Jalan Tungku Link, Gadong BE, Negara, BE 1410 Brunei Darussalam
There is much speculation over whether elevational gradients in physical systems will
change as a result of future climate warming. A fundamental factor in controlling
elevational gradients is air temperature. Yet there is little agreement about whether lapse
rates as observed at the mountain surface (rather than in the free atmosphere) are
weakening or increasing in a warmer world. Both increases in lapse rate due to enhanced
snow cover at high elevations, and decreases in lapse rate due to rapid snowmelt have
been suggested as possible consequences. This study examines 1084 long-term high
elevation temperature records from the homogeneity adjusted Global Historical Climate
Network (GHCN) and Climate Research Unit (CRU) datasets for 1948-1998. Temporal
trends in monthly temperature anomalies are examined by continent and for elevational
bands (from 500 m to 4700 m). Although nearly half of sites show significant warming,
there are no global relationships between trend magnitude and elevation. There is a weak
decrease in warming rate with elevation in South America, in contrast to free-air trends as
measured by the NCEP/NCAR reanalysis which show enhanced warming at higher
elevations. Lapse rates between groups of stations show variable trends depending on
continent and aspect. Thus we cannot generalise whether warming is amplified or
damped at higher elevations. The effects of the degree of urbanisation, vegetation and
local topography are also examined. Variance in trend magnitudes is increased at
mountain valley locations, as compared to mountain summits which show more
consistent trends.
C33C-1280
An Embedded Sensor Network for Measuring Elevation Effects on Temperature,
Humidity, and Evapotranspiration Within a Tropical Alpine Valley
Hellstrom, R A (rhellstrom@bridgew.edu) , Geography Department, Bridgewater State
College, Conant Science Building, Bridgewater, MA 02325, United States
* Mark, B G (mark.9@osu.edu) , Department of Geography, The Ohio State University,
1036 Derby Hall, 154 N Oval Mall, Columbus, OH 43210, United States
Conditions of glacier recession in the seasonally dry tropical Peruvian Andes motivates
research to better constrain the hydrological balance in alpine valleys. Studies suggest
that glaciers in the tropical Andes are particularly sensitive to seasonal humidity flux due
to the migration of the Intertropical Convergence Zone. However, there is an outstanding
need to better measure and model the spatiotemporal variability of energy and water
budgets within pro-glacial valleys. In this context, we introduce a novel embedded
network of low-cost, discrete temperature and humidity microloggers and an automatic
weather station installed in the Llanganuco valley of the Cordillera Blanca. This paper
presents data recorded over a full annual cycle (2004-2005) and reports on network
design and results during the dry and wet seasons. The transect of sensors ranging from
about 3500 to 4700 m reveal seasonally characteristic diurnal fluctuations in up-valley
lapse rate. A process- based water balance model (Brook90) examines the influence of
meteorological forcing on evapotranspiration (ET) rates in the valley. The model results
suggest that cloud-free daylight conditions enhances ET during the wet season. ET was
insignificant throughout the dry season. In addition, we report on the effects of elevation
on ET.
C33C-1281
Mountain system monitoring at Senator Beck Basin, San Juan Mountains, Colorado
* Landry, C C (clandry@snowstudies.org) , Center for Snow and Avalanche Studies, PO
Box 190, Silverton, CO 81433, United States
Lyon, P (peglyon@ocinet.net) , Colorado Natural Heritage Program, Colorado State
University College of Natural Resources 254 General Services, Fort Collins, CO 80523-
6021, United States
Painter, T H (tpainter@nsidc.org) , National Snow and Ice Data Center, Univ. of
Colorado at Boulder 449 UCB, Boulder, CO 81433, United States
Barrett, A P (apbarret@kryos.colorado.edu) , National Snow and Ice Data Center, Univ.
of Colorado at Boulder 449 UCB, Boulder, CO 81433, United States
Alpine mountain systems exhibit particular sensitivity to climate change in the form of
altered patterns in plant communities, snowcover and hydrologic characteristics,
biogeochemical fluxes, and energy budgets. Monitoring of such systems, across
elevational gradients, and using an integrative approach, could yield early evidence of
long-term trends in local and regional mountain processes and the ecological and
economic services they provide. Climate change and ecological modelers can also
eventually benefit from field verification of their forecasts. To these ends, the Senator
Beck Basin Study Area has been developed in the western San Juan Mountains, a high
altitude, mid-latitude, continental mountain range located in southwest Colorado, USA.
This 290 ha 'headwater' catchment spans elevations from 3353 to 4118 m, a gradient that
captures alpine (arctic-like) tundra at the highest elevations, sub-alpine forest at the
lowest, and the dynamic krumholz ecotone between. Seasonal snowcover dominates this
landscape for up to nine months per year, and monitoring and research infrastructure has
been conceived and developed to capture this (mountain) snow system's behaviors. Two
extensive arrays of instrumentation monitor weather, snowpack, energy budget, and basic
soil condition parameters. A stream gauge at the basin pour point monitors streamflow
and basic water properties. Routine snow profiles monitor snowpack properties adjacent
to the micro-met sites. And, a comprehensive inventory of the basin's plant communities
was performed in 2004, at three elevational bands, and field monuments were installed to
facilitate routine repeat studies. Significantly different populations and degrees of
diversity were found at each elevational band. Researchers currently being hosted in the
basin are exploring the effects of desert dust depositions on alpine snowpack, hydrologic,
biogeochemical, and climatic processes, at multiple spatio-temporal scales. Comparable
integrative research projects utilizing the Senator Beck Basin Study Area are encouraged,
and collaborators are sought for the continued development of an integrated monitoring
and research program supporting investigations of interactions driving, being driven by,
and otherwise comprising the mountain (snow) system.
http://www.snowstudies.org/
C33C-1282
The Community Collaborative Rain, Hail and Snow Network (CoCoRaHS):
Documenting Local Precipitation Gradients in the Populated Areas of the Rocky
Mountain West
Doesken, N (nolan@atmos.colostate.edu)
* Reges, H (hreges@atmos.colostate.edu)
Many natural resources planning, management and research efforts in the Western U.S.
require reasonable estimates of precipitation in complex terrain. Long-term data sources
for documenting precipitation patterns are sparse, however. The Community
Collaborative Rain, Hail and Snow network (CoCoRaHS) is a low cost approach to
documenting local precipitation gradients in the populated areas of the Rocky Mountains
west. Several hundred volunteer observing sites have now been operated for several years
on both sides of the Continental Divide in Colorado. Preliminary results indicate very
good data quality from most observing sites, even in the winter months. Example
elevation gradients and year to year as well as storm to storm variations will be shown for
several counties in Colorado and compared with 30-year average gradients from those
same areas estimated by the PRISM maps produced by Oregon State University.
Opportunities to expand CoCoRaHS to other parts of the Western U.S. will be discussed.
http://www.cocorahs.org
C33C-1283
Modeling Climate Change impacts on Snow Water Equivalent (SWE) in Alpine
Headwaters, Glacier National Park, MT
* Larson, R P (robert.larson@uleth.ca) , Water and Environmental Science, University of
Lethbridge, Lethbridge, AB T1K3M4 Canada
Byrne, J M (byrne@uleth.ca) , Water and Environmental Science, University of
Lethbridge, Lethbridge, AB T1K3M4 Canada
Kienzle, S (stefan.kienzle@uleth.ca) , Water and Environmental Science, University of
Lethbridge, Lethbridge, AB T1K3M4 Canada
Letts, M (matthew.letts@uleth.ca) , Water and Environmental Science, University of
Lethbridge, Lethbridge, AB T1K3M4 Canada
Johnson, D (dan.johnson@uleth.ca) , Water and Environmental Science, University of
Lethbridge, Lethbridge, AB T1K3M4 Canada
GCMs generally forecast marginal increases in winter precipitation, and substantial
increases in winter temperatures for the St. Mary River headwaters in Glacier National
Park, Montana under climate warming. Details assessments are needed to predict whether
increased winter precipitation will compensate for increasing temperatures in spring SWE
and associated water supply. The objectives of this study are twofold: first, to develop an
alpine hydrometeorology model for predicting SWE over the upper St. Mary watershed;
and second, to apply the model for historical and future climate scenarios to estimate
potential impacts of climate change on water supply in the basin. This poster describes
the work carried out to address the first objective. A distributed hydrometeorology model
has been adopted to simulate temperature variations according to aspect, slope, and
elevation, and was validated for three aspects on a nearby mountain site in WatertonLakes National Park. Snow course data, spanning an elevation band of 1400 m to 2300 m
within the St. Mary headwaters (representing over 80 percent of the study area), was used
to develop precipitation-elevation relationships for incorporation into the
hydrometeorology model. SWE was simulated with the model for a daily time step for
the historical study period, and spring SWE fields were compared to spring runoff
volumes.
C33C-1284
The Cariboo Alpine Mesonet
MacLeod, S (macleods@unbc.ca) , University of Northern British Columbia, 3333
University Way, Prince George, BC V2N 4Z9 Canada
* D\'ery, S (sdery@unbc.ca) , University of Northern British Columbia, 3333 University
Way, Prince George, BC V2N 4Z9 Canada
It is projected that climate change will have an amplified impact on the hydroclimate of
mountainous areas such as northern British Columbia (BC), Canada. In response to rising
air temperatures, permafrost will thaw, glaciers will recede, the seasonal snowpack will
thin, and precipitation is likely to increase due to the enhanced water holding capacity of
warmer air. Unfortunately, there exist few longterm climatic records at high altitude sites
in the North American Cordillera. This poster will describe the recent deployment of the
"Cariboo Alpine Mesonet" (CAM) that will partly fill this gap by generating a longterm
climatic record for the Quesnel River drainage basin in the Cariboo Mountains of BC.
CAM is a network four of meteorological stations installed at high elevation sites within
the Quesnel watershed. Stations at Spanish Mountain (el. 1509 m), Blackbear Mountain
(el. 1590 m), Browntop Mountain (el. 2030 m), and at the University of Northern British
Columbia's Quesnel River Research Centre (el. 743 m) all measure wind speed and
direction, precipitation, air temperature, relative humidity, atmospheric pressure, soil
temperature, and snow depth. Preliminary results focusing on the effects of elevation on
various meteorological quantities will be presented. Future opportunities for the
expansion of CAM will also be discussed.
http://web.unbc.ca/~sdery/CAM/
C33C-1285
Earlier streamflow in the Sierra Nevada: influence of elevation on detectability of past
and projected trends
* Maurer, E P (emaurer@engr.scu.edu) , Civil Engineering Department Santa Clara
University, 500 El Camino Real, Santa Clara, San 95053-0563, United States
Stewart, I T (IStewartFrey@scu.edu) , Environmental Studies Program Santa Clara
University, 500 El Camino Real, Santa Clara, San 95053, United States
Bonfils, C (bonfils2@mail.llnl.gov) , School of Natural Sciences University of
California, Merced, U.C. Merced, Merced, CA 95344, United States
Duffy, P B (pduffy@llnl.gov) , Lawrence Livermore National Laboratory, Lawrence
Livermore National Laboratory, Livermore, CA 94551, United States
Cayan, D (dcayan@ucsd.edu) , Climate Research Division, Scripps Institution of
Oceanography and Water Resources Division, US Geological Survey, UCSD 201
Nierenberg Hall, La Jolla, CA 92093-0224, United States
We examine the seasonal timing of flows on four major rivers in California, and how
these are affected by climate variability and change. We measure seasonal timing of soil
runoff and river flows by the "center timing" (CT), defined as the day when half the
annual flow has passed a given measurement point. We use a physically-based surface
hydrologic model driven by meteorological input from a global climate model to quantify
the year-to-year variability in CT resulting from natural internal climate variability (the
internal oscillations of the climate system). We find that estimated 50-year trends in CT
due to natural internal climate variability often exceed the trends in CT observed over the
last 50 years. Thus, although observed trends in CT may be statistically significant, they
are not necessarily a result of external influences on climate such as increased greenhouse
gases. To estimate when CT changes might be expected to exceed levels possible from
natural climate variability, we calculate the sensitivity of CT to increases in temperature
ranging from 1 to 5 degrees. We find that at elevations between 2000
â€â€œ 2800 m are most sensitive to temperature increases in this range,
and can experience changes in CT exceeding 45 days. As temperatures rise, so do the
elevations that are most sensitive to further increases in temperature. Based on these
sensitivities, we estimate that changes in CT will exceed those possible from natural
climate variability by the mid- or late 21st century, depending on rates of future
greenhouse gas emissions.
C33C-1286
The 16 May 2005 Flood in Yosemite National Park--A Glimpse into High-Country Flood
Generation in the Sierra Nevada
* Dettinger, M (mddettin@usgs.gov) , US Geological Survey, Scripps Institution of
Oceanography Dept 0224, 9500 Gilman Drive, La Jolla, CA 92093, United States
Lundquist, J (jdlund@u.washington.edu) , Department of Civil and Environmental
Engineering, University of Washington, Seattle, WA 98195, United States
Cayan, D (dcayan@ucsd.edu) , US Geological Survey, Scripps Institution of
Oceanography Dept 0224, 9500 Gilman Drive, La Jolla, CA 92093, United States
Meyer, J (joe_meyer@nps.gov) , National Park Service, Yosemite National Park, El
Portal, CA 95389, United States
On 16 May 2005, a Pacific storm drew warm, wet subtropical air into the Sierra Nevada,
causing moderate rains and major flooding. The flood raised Hetch Hetchy and Tenaya
Lake levels markedly and inundated large parts of Yosemite Valley, requiring
evacuations and raising public-safety concerns in Yosemite National Park. This was the
first major flood to be recorded by the high-country hydroclimatic network in the Park.
Since 2001, scientists from US Geological Survey, Scripps Institution of Oceanography,
California Department of Water Resources, National Park Service, and other institutions
have developed the network of over 30 streamflow and 50 air- temperature loggers at
altitudes ranging from < 1500 m to >3000 m above sea level, and 8 snow-
instrumentation sites measuring snow-water contents, snow depths, radiation, soil
moisture, and temperatures in air, snow, and soil. The network documented flooding that
derived its runoff mostly from high-altitude rainfall on soils already wet due to the onset
of snowmelt a few days earlier. Air temperatures during the storm were above freezing
up to altitudes of nearly 3000 m, so that rain fell to as high as 3000 m, compared with
normal winter snowlines nearer 1500 m. Streams flooded below 3000 m, and above that
altitude did not flood or contribute much to the flooding below. Meanwhile, no
significant snow-water content changes were measured. Thus this flood resulted from
rain-through-snow runoff rather than rain-on-snow melting. In the Park as a whole, about
five times more catchment area received rain, rather than snow, during this storm than
during typical cool winter storms. Because the flood was more a result of the large area
that received rainfall than of melting snow, snowpack reductions that are expected if
recent warming trends continue would not have reduced the flood. Instead, the
opportunity for warm storms may increase if warming continues, in which case the
potential for this kind of flooding will increase.
C33C-1287
Drought � how the Western U.S. is Transformed from Energy-limited to Water-limited
Landscapes
* Hidalgo, H G (hhidalgo@ucsd.edu) , Scripps Institution of Oceanography, University
of California, San Diego 9500 Gilman Drive, MC 0224, La Jolla, CA 92093
Cayan, D R (dcayan@ucsd.edu) , Scripps Institution of Oceanography, University of
California, San Diego 9500 Gilman Drive, MC 0224, La Jolla, CA 92093
Cayan, D R (dcayan@ucsd.edu) , United States Geological Survey, University of
California, San Diego 9500 Gilman Drive, MC 0224, La Jolla, CA 92093
Dettinger, M D (mdettinger@ucsd.edu) , Scripps Institution of Oceanography, University
of California, San Diego 9500 Gilman Drive, MC 0224, La Jolla, CA 92093
Dettinger, M D (mdettinger@ucsd.edu) , United States Geological Survey, University of
California, San Diego 9500 Gilman Drive, MC 0224, La Jolla, CA 92093
Simulations of the western United States' (US) hydrology using the Variable Infiltration
Capacity were used to quantify the effects of drought and climate change on the
landscape's aridity. An index of aridity based on the ratio of actual to potential
evapotranspiration (AET/PET) was calculated for years of extreme droughts and pluvials
and for altered conditions of precipitation (P) and average temperature (Tavg). In the high
elevations increases in aridity are related to reductions in the areas where AET rates can
be considered energy-limited, while in the low elevations increases in aridity are
associated with increases in aridity that in the long-term can lead to desertification. In
terms of the shifts in the climatological aridity, the overall changes in the arid regions are
on the order of 3-4 percent of the area of the West that would switch from semiarid to
arid for a change in 3oC or 5 percent decrease in P. This is significant, as it constitutes an
expansion of around 18 percent of the current arid areas of the west. The reduction of the
energy-limited areas to water limited for the warming scenario represents a reduction of
17 percent of the available energy-limited (humid and semi-humid) areas. This represents
an important reduction in the mean moisture availability in the high-elevation regions.
Drought can impose large year-to-year variability in the aridity of the West landscape,
making it difficult to distinguish the future climate change signals in aridity from natural
variability.
C33C-1288
Elevation-Aspect Interactions at the Subarctic Alpine Treeline
* Danby, R (rdanby@ualberta.ca) , University of Alberta, Department of Biological
Sciences, Edmonton, AB T6G 2E9 Canada
Hik, D (dhik@ualberta.ca) , University of Alberta, Department of Biological Sciences,
Edmonton, AB T6G 2E9 Canada
Clarke, G (clarke@eos.ubc.ca) , University of British Columbia, Department of Earth and
Ocean Sciences, Vancouver, BC V6T 1Z4 Canada
Kavanaugh, J (jeff.kavanaugh@ualberta.ca) , University of Alberta, Department of Earth
and Atmospheric Sciences, Edmonton, AB T6G 2E3
Martin, K (kmartin@interchange.ubc.ca) , University of British Columbia, Department of
Forest Sciences, Vancouver, BC V6T 1Z4 Canada
Flowers, G (gflowers@sfu.ca) , Simon Fraser University, Department of Earth Sciences,
Burnaby, BC V5A 1S6 Canada
The southwest Yukon contains Canada's highest mountain range and has experienced
rapid climate change over the past decade. Glacial margins and the forest-tundra ecotone
represent the most significant landscape boundaries in the region. Forest-tundra ecotone
dynamics are thought to be heavily influenced by thermal elevational gradients. As
temperature increases, treeline is expected to advance, with significant implications for
the region's ecology as a result. However, accurate predictions of these changes are
contingent on knowledge of (i) past responses to climate change and (ii) the extent to
which pattern and process at treeline is mediated by factors other than temperature. To
this end, we present results of a six-year hierarchical study of treeline that included
experimental warming, dendroecology, repeat photography, and species distribution
modeling. Integration of results from each investigation confirms that the elevational
temperature gradient has the most significant influence on ecological pattern and process
across the ecotone. However, solar radiation � controlled by aspect and surrounding
topography � was also identified as a significant influence at each spatial and temporal
scale of analysis. Moreover, elevation and aspect interact to create multiple positive and
negative system feedbacks that result in nonlinear vegetation dynamics. In tandem with
the development of an ecotone dynamics model, we are developing climate-forced
physical models to describe changes in ground thermal regime and glacier extent.
Collectively, these results are being used to catalyze an interdisciplinary International
Polar Year collaboration aimed at modeling landscape responses to future climate change
in the region.
C33C-1289
Elevational Gradients and Differential Recruitment of Limber Pine (Pinus flexilis) and
Bristlecone Pine (P. longaeva); White Mountains, California, USA
* Millar, C I (cmillar@fs.fed.us) , USDA Forest Service, Sierra Nevada Research Center,
PO Box 245, Berkeley, CA 94701, United States
Westfall, R D (bwestfall@fs.fed.us)
Delany, D L (ddelany@fs.fed.us)
Subalpine and alpine plant communities commonly are assumed to respond to warming
temperatures by shifting upslope relative to their current elevational positions and
proportional to their current elevational niche breadths. We studied recruitment of limber
pine (Pinus flexilis, PiFl) and bristlecone pine (P. longaeva, PiLo) at 8 sites in the
southern White Mtns of California: 3 at and above current upper treeline for the species,
2 at middle elevations; and 3 at and below lower treeline. During the last several
centuries in White Mtn populations, PiLo extended ca 150 m higher in elevation than
PiFl, while both species had similar lower treeline elevations. PiLo extended historically
higher and lower than PiFl on dolomite as compared to granitic and shale/sandstone
substrates. We aged pine recruitment (less than 100 yrs old) by branch whorl counts
(seedlings less than 5 cm stem dia) and growth-ring counts (greater than 5 cm dia) along
transects extending below lower treeline, into basins and depressions at middle
elevations, and extending above treeline at upper elevations. PiFl exceeded PiLo in
abundance of recruits at all sites. At lower and middle elevations the 45-65 yr-old age
class was most abundant. At lower elevations, recruitment was limited to narrow, westand north-facing ravines; at middle elevations, recruitment occurred within the general
forest zone and also into sagebrush (Artemisia spp)dominated depressions and basins of
the mid-elevation plateaus. At upper elevation, PiFl abundance overall exceeded PiLo by
more than 400%; on dolomite substrates PiFl was often the only recruiting species at the
highest elevations and above current treeline. The seedling class (less than 30 yrs old)
dominated in both species, with the 45-65 yr age class next in abundance. In each case at
high elevations, PiFl recruitment occurred where no mature live PiFl was present within
200 m downslope; in one case PiFl recruitment occurred 100 m above current treeline,
extending into areas where large historic deadwood stems of PiLo exist We make the
tentative conclusion that PiFl is recruiting abundantly at low to high elevations in the
White Mountains and greatly exceeds PiLo recruitment at upper elevations and above
current upper treeline. PiFl appears to be advancing in dominance over PiLo in the White
Mountains during the 21st century.
C33C-1290
Persistent Cold Air Drainage and Modeled Nocturnal Leaf Water Potential in Complex
Forested Mountainous Terrain
Gray, L (liag03@hampshire.edu) , University of Idaho, College of Natural Resources,
Department of Forest Resources, Moscow, ID 83843, United States
* Hubbart, J A (hubb8662@uidaho.edu) , University of Idaho, College of Natural
Resources, Department of Forest Resources, Moscow, ID 83843, United States
Kavanagh, K (katyk@uidaho.edu) , University of Idaho, College of Natural Resources,
Department of Forest Resources, Moscow, ID 83843, United States
Link, T E (tlink@uidaho.edu) , University of Idaho, College of Natural Resources,
Department of Forest Resources, Moscow, ID 83843, United States
Pangle, R (pang1809@uidaho.edu) , University of Idaho, College of Natural Resources,
Department of Forest Resources, Moscow, ID 83843, United States
Spatial variations in microclimate related to air temperature inversions play an important
role in determining the timing and rate of many biophysical processes. Inversions are of
particular interest in mountainous regions where cold air drainage flows can greatly
enhance the depth and extent of these patterns. Recent work demonstrated that stomata do
not close completely at night resulting in nocturnal transpiration. This study was designed
to improve our understanding of nocturnal inversions and subsequent impacts on the
accuracy and spatial gradients of predawn leaf water potential ($\Psi$pd) used as a
surrogate for soil water potential ($\Psi$s). Eight temperature data loggers were installed
in transect spanning a 155 m vertical distance on a northerly facing slope in the Mica
Creek Experimental Watershed (MCEW) in northern Idaho during July and August 2004.
Strong nocturnal temperature inversions typically spanned the lower 88 vertical meters.
Observed lapse rates were 29.0, 27.0, and 25.0 $\deg$/km at 00:00, 04:00, and 20:00hrs
respectively, based on mean temperatures for both months. At this scale (i.e., < 1km), the
observed lapse rates resulted in large differences in nocturnal vapor pressure deficits (D)
over the length of the slope, and correspondingly large differences on the modeled
disequilibrium between soil and leaf water potential. Parameters obtained at the Priest
River Experimental Forest (PREF) in northern Idaho were used to assess the
disequilibrium between modeled $\Psi$pd and $\Psi$s and included nocturnal stomatal
conductance (gs-noc), and leaf specific conductance (KL). Field studies showed that
these parameters were similar at both the MCEW and the PREF, except for gs-noc for
Douglas-fir (${\it Pseudotsuga menziesii}$), which was found to be 63% higher at the
MCEW. In response to cold air drainage, modeled $\Psi$pd grew consistently more
negative at higher elevations up to - 0.3 MPa during nocturnal hours based on mean
temperatures. Strong nocturnal inversions on the lower 88 m of the slope resulted in leaf
water potentials that were more negative by at least 30% and 50% based on mean and
maximum temperatures respectively from the bottom of the slope to the top of the
inversion layer. On a cloudy night, with low D, the maximum decrease in $\Psi$pd along
the slope was - 0.04 MPa. Results of this work indicate that given persistent cold air
drainage, and potentially nocturnally active stomata, errors could be made in estimating
$\Psi$s when using standard methodologies and assumptions. These results hold
important implications for the application of distributed ecological and hydrological
models in complex forested terrain.
http://www.cnr.uidaho.edu/micacreek/
C33C-1291
Chemical weathering rates along a steep climate gradient in the Idaho Batholith
* Ferrier, K L (ferrier@eps.berkeley.edu) , Department of Earth and Planetary Science,
University of California, Berkeley, 340 McCone Hall University of California, Berkeley,
Berkeley, CA 94720-4767, United States
Kirchner, J W (kirchner@eps.berkeley.edu) , Department of Earth and Planetary Science,
University of California, Berkeley, 340 McCone Hall University of California, Berkeley,
Berkeley, CA 94720-4767, United States
Finkel, R C (finkel1@llnl.gov) , Center for Accelerator Mass Spectrometry, Lawrence
Livermore National Laboratory, P.O. Box 808 L-206, Livermore, CA 94550, United
States
Chemical weathering plays a major role in many Earth surface processes. It regulates
rates of landscape evolution, supplies nutrients to soils and streams, and contributes to
geochemical cycling. Over long timescales (> 1 Myr), chemical weathering of silicate
minerals is the dominant sink for atmospheric carbon dioxide. If silicate chemical
weathering rates increase with temperature (as theory and experiments suggest they
should), then chemical weathering ought to draw down atmospheric carbon dioxide more
rapidly at higher temperatures, thereby buffering Earth's temperature via the greenhouse
effect. Quantifying the strength of this coupling between chemical weathering rates and
temperature is thus particularly important to understanding Earth's long-term climatic
evolution. Mountain transects that span a wide range in elevation (and hence a wide
range in temperature) offer natural laboratories for studying the dependence of chemical
weathering rates on climate. Because chemical weathering weakens rock and releases
nutrients to soil, variations in chemical weathering rates along an elevation transect
should also lead to variations in physical erosion rates, soil development, and biotic
activity. The canyon of the South Fork of the Salmon River in the granitic Idaho
Batholith is home to such an elevation transect, with neighboring Pilot Peak rising 1500
meters above the river over a horizontal distance of 5000 meters. The chemical
weathering rate at a particular elevation can be determined by combining measurements
of denudation rate (inferred from measurements of cosmogenic $^{10}$Be in quartz)
with measurements of immobile element enrichment in soil relative to parent bedrock. In
order to measure chemical weathering rates across this climate transect, we have
collected rock and soil samples at a series of elevations along the southwestern spur of
Pilot Peak. Preliminary measurements of immobile element enrichment in soil relative to
parent bedrock show that the degree of chemical weathering increases with temperature,
as expected. These data are consistent with an effective activation energy of 40 kJ/mol,
comparable to literature values for feldspar activation energies.
C33C-1292
Glaciological observations in Suntar-Khayata Range, Eastern Siberia, in 2004- 2005
* TAKAHASHI, S (shuhei@mail.kitami-it.ac.jp) , Kitami Institute of Technology, Koencho 165, Kitami, 090-8507 Japan
SUGIURA, K (sugiura@jamstec.go.jp) , JAMSTEC, Natsusima-cho 2-15, Yokosuka,
237-0061 Japan
KAMEDA, T (kameda@mail.kitami-it.ac.jp) , Kitami Institute of Technology, Koen-cho
165, Kitami, 090-8507 Japan
KONONOV, Y (jukon@mail.ru) , Institute of Geography, Staromoetony 29, Moscow,
109017 Russian Federation
ANANICHEVA, M D (cest@online.ru) , Institute of Geography, Staromoetony 29,
Moscow, 109017 Russian Federation
As an activity of IPY (International Polar Years), Glaciological and meteorological
observations were done in the area of Suntar-Khayata Range in 2004-2005, where
extensive glaciological studies were made by research groups of Russian Academy in
IGY Period, around 1957. In 2004-2005, meteorological data were obtained at the
terminus of Glacier No. 31 in Suntar- Khayata Range and at several points in Oimiyakon
area. The minimum temperature in a year was -59 C at Oimiyakon (about 680 m a.s.l.),
which is called �gPole of Cold�h, and -45 C at Glacier No. 31 (about 2050 m a.s.l.),
which suggests there was strong temperature-inversion in this area in the period of
Siberia high pressure in winter. Glacier extent variation in this 50-year period will be
examined by the satellite image analysis. According to a research of moraine length
change in this area (Ananicheva et al., 2005), retreat of glacier in length from Little Ice
Age to present time was about 10% in the northern massif of Suntar-Khayta, and 10-20%
in the southern massif.
C33C-1293
Mass-Balance Fluctuations of Glaciers in the Pacific Northwest and Alaska, USA
* Josberger, E G (ejosberg@usgs.gov) , US Geological Survey, Washinton Water
Science Center, 934 Broadway, Suite 300, Tacoma, WA 98402, United States
Bidlake, W R (wbidlake@usgs.gov) , US Geological Survey, Washinton Water Science
Center, 934 Broadway, Suite 300, Tacoma, WA 98402, United States
March, R S (rsmarch@usgs.gov) , Us Geological Survey, Alaska Science Center, 3400
Shell Street, Fairbanks, AK 99701, United States
Kennedy, B W (bkennedy@usgs.gov) , Us Geological Survey, Alaska Science Center,
3400 Shell Street, Fairbanks, AK 99701, United States
The mass balance of mid-latitude glaciers of the Pacific Northwest and southern Alaska
fluctuates in response to changes in the regional and global atmospheric climate. More
than 40 years of net and seasonal mass balance records by the U.S. Geological Survey for
South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, show
annual and inter-annual fluctuations that reflect the controlling climatic conditions. South
Cascade and Wolverine Glaciers are strongly affected by the warm and wet maritime
climate of the Northeast Pacific Ocean, and the winter balances are strongly related to the
Pacific Decadal Oscillations (PDO). Gulkana Glacier is more isolated from maritime
influences and the net balance variation is more closely linked to the summer balance. By
the late 1970's, mass-balance records for the three were long enough to reflect the 197677 shift in PDO from negative to positive. Both maritime glaciers responded, with net
balance of South Cascade Glacier becoming consistently negative and that of Wolverine
Glacier becoming predominantly positive. The overall trend of negative mass balance
continued through 2004 for South Cascade Glacier, where the 1977 to 2004 cumulative
net balance was about -22 meters water equivalent (mweq). After a gain of about 7
mweq, the trend of positive net balance for Wolverine Glacier ended in 1989. Beginning
in 1989, the net balance trend for Wolverine Glacier became predominantly negative and
the cumulative net balance for 1989 to 2004 was about - 14 mweq. Net balance of
Gulkana Glacier did not respond appreciably to the 1976-77 PDO shift. The cumulative
net balance for Gulkana Glacier from the beginning of the record (1966) through 1988
was about -3 mweq. The major change in trend of mass balance occurred in 1989, when
net balance became almost exclusively negative. The cumulative net balance during 1989
through 2004 was about �13 mweq. As a result trends in net balance had become
strongly negative for more than a decade at all three bench mark glaciers.
http://ak.water.usgs.gov/glaciology/
C33C-1294
Effect of the Penetration of Solar Radiation Through Surface Snow Cover on Albedo of
July 1st Glacier, China
* Matsuda, Y (matsuda_snowman@nagoya-u.jp) , Nagoya University, c/o HyARC,
Nagoya University Furo-cho, Chikusa-ku,, Nagoya, 464-8601 Japan
Sakai, A (shakai@nagoya-u.jp) , Nagoya University, c/o HyARC, Nagoya University
Furo-cho, Chikusa-ku,, Nagoya, 464-8601 Japan
Fujita, K (cozy@nagoya-u.jp) , Nagoya University, c/o HyARC, Nagoya University
Furo-cho, Chikusa-ku,, Nagoya, 464-8601 Japan
We use albedo model to evaluate the effect of the penetration of solar radiation through
surface snow cover on albedo at three sites in the lower ablation area of July 1st glacier,
China, during summer 2004. When the depth of the surface snow cover is not so deep,
the albedo of snow-covered glacier surface is affected by the underlying ice due to the
penetration of solar radiation. Besides the absorption of solar radiation into the snow,
solar radiation can be also absorbed into the underling ice. Therefore it is possible that the
surface snow does not melt at all, even though total energy flux from atmosphere to
glacier is positive. When the penetration of solar radiation is disregarded, simulated
surface albedos fluctuate widely due to the alternation of rapid snow melting and frequent
snowfall and they tend to be lower than observed albedos. Root-mean-square differences
between observed and simulated surface albedo during summer 2004 are 0.14 - 0.17
when penetration of solar radiation is ignored, and 0.10 - 0.12 when penetration of solar
radiation is considered. The averages of the difference of absorbed solar radiation derived
from the albedo difference are 6.0 - 16.1 W m$^{-2}$ when penetration of solar radiation
is ignored, and 3.9 - 10.0 W m$^{-2}$ when penetration of solar radiation is considered.
C33C-1295
Summer Air Temperature Lapse Rates in a Glaciated Alpine Catchment, Northwestern
British Columbia, Canada
* Boon, S (boon@unbc.ca) , Geography Program, University of Northern British
Columbia, 3333 University Way, Prince George, BC V2N 4Z9 Canada
Air temperature lapse rates are often used in numerical models of alpine glacier mass
balance to extrapolate data from a single meteorological station to locations distant from
that station. As field measurements of alpine air temperature lapse rates are limited,
however, they are often assumed to be constant at $-6\deg$C km$^{-1}$ (moist adiabatic
lapse rate; MALR). Three meteorological stations were installed at 585 m, 1180 m and
1887 m asl in the Andrei Glacier catchment, northwestern British Columbia ($56\deg$
55' N, $130\deg$ 55' W), during the latter half of the summer 2006 melt season. Each
station measured hourly average air temperature ($\deg$C) at 2 m above the surface.
These data were used to calculate the temporal distribution of hourly and daily
temperature lapse rates in the region, and determine their proximity to the MALR.
Temporal patterns in daily air temperature lapse rates were then compared with gridded
daily synoptic maps from the Meteorological Service of Canada (surface, 500 mb, 700
mb, and 850 mb), to determine if specific synoptic configurations correlate with specific
lapse rate characteristics. Results suggest that regional synoptic data may be highly useful
for deriving local air temperature lapse rates in areas with sparse local field
measurements, thus producing more accurate model output than that produced using the
constant MALR. These data may also be used to develop methods for downscaling GCM
output to derive regional climate change scenarios. However, depending on the extent of
the glacier boundary layer, local microclimatic perturbations may decouple local air
temperature lapse rates from the regional synoptic configuration.
C33C-1296
Mass Balance and Climate of the Ablation Zone of the Taylor Glacier, Antarctica
* Bliss, A K (andybliss@gmail.com) , University of California at Berkeley, Department
of Geography 507 McCone Hall, Berkeley, CA 94720, United States
Cuffey, K M (kcuffey@berkeley.edu) , University of California at Berkeley, Department
of Geography 507 McCone Hall, Berkeley, CA 94720, United States
We explore the relationships between climate and ablation on the Taylor Glacier on
hourly to annual timescales. A simple physically-based model that predicts ablation from
weather station measurements on the Taylor Glacier, Antarctica is presented along with
ablation measurements at about 250 ablation stakes. Case studies of low, median, and
high ablation events are presented. Advanced Very High Resolution Radiometer imagery
and NOAA-NCEP Reanalysis data are included in the analysis to give the broader
context of the weather station measurements and to help connect the local scale of
weather station measurements to the broader scale of climate model output. A novel
method of visualizing these disparate data is also demonstrated.
http://geography.berkeley.edu/~abliss/
C33C-1297
Identification of Antarctic ablation areas using a regional atmospheric climate model
* Van den Broeke, M (broeke@phys.uu.nl) , Utrecht University, PO Box 80005, Utrecht,
3508TA Netherlands
Van de Berg, W (w.j.vandeberg@phys.uu.nl) , Utrecht University, PO Box 80005,
Utrecht, 3508TA Netherlands
Van Meijgaard, E (vanmeijg@knmi.nl) , Royal Netherlands Meteorological Institute, PO
Box 201, De Bilt, 3730AE Netherlands
The occurrence of Antarctic ablation areas in Dronning Maud Land, the Lambert Glacier
Basin, Victoria Land, the Transantarctic Mountains and the Antarctic Peninsula is
realistically predicted by the regional atmospheric climate model RACMO2/ANT, with
snowdrift-related processes calculated offline. Antarctic ablation areas are characterized
by a low solid precipitation flux in combination with strong sublimation, snowdrift
erosion and/or melt. The strong interaction between atmospheric circulation and
topography plays a decisive role in the precipitation distribution and hence that of
ablation areas. Three types of Antarctic ablation areas can be distinguished, all occurring
in dry regions: Type 1 is the erosion-driven ablation area, caused by 1D and/or 2D
divergence in the katabatic wind field at high elevations (2000-3200 m asl). Type 2 is the
sublimation-driven ablation area. This type occurs at lower elevations ( < 2000 m)
preferably at the foot of steep topographic barriers, where temperature and wind speed
are high and relative humidity low. Type 3 represents the melt-driven ablation area,
occurring in the northern Antarctic Peninsula. Combinations of types 1/2 and 2/3 are
possible. Over the period considered here (1980-2004), no significant trend is found in
the total area covered by Antarctic ablation areas, which equals about 2 % of the total ice
sheet surface (including ice shelves).
C33C-1298
Impact of Anthropogenic Urban Heat Island on Snowmelt at Barrow, Alaska
* Hinkel, K M (Kenneth.Hinkel@uc.edu) , University of Cincinnati, Department of
Geography, Cincinnati, OH 45221, United States
Nelson, F E (fnelson@udel.edu) , University of Delaware, Department of Geography,
Newark, DE 19716, United States
The village of Barrow (71 N latitude) is the largest native community in the Arctic, with
a population of approximately 4500 people. Situated on the coast of the Arctic Ocean in
northernmost Alaska, the area is entirely underlain by permafrost. Although most
supplies must be imported, Barrow relies on local natural gas fields to meet all energy
requirements for building heat and electrical power generation. This energy eventually
dissipates into the atmosphere, and can be detected as a pronounced urban heat island
(UHI) in winter. Since 2001, a 150 km2 area in and around Barrow has been monitored
using 70 data loggers recording air temperature at hourly intervals. The mean daily
temperature of the urban and rural areas is calculated using a representative sample of
core sites, and the UHI magnitude (MUHI) calculated as the difference in the group
averages. The MUHI is most pronounced in winter months (December-March), with
temperatures in the urban area averaging 2�C warmer than in the surrounding tundra
and occasionally exceeding 6�C. The MUHI is maximized under cold and calm
conditions, and decreases with wind speed and warmer temperatures. It is strongly and
directly correlated with natural gas utilization on a monthly basis. Integrated over the
home heating season, there is an 8% reduction in freezing degree days in the village. The
timing makes it unlikely that anthropogenic heat contributes to the forward shift in the
snow meltout date that has been observed near Barrow over the past 60 years.
C33C-1299
Modeling the Onset of Spring Snowmelt in a Large-scale Northern Rockies Watershed
* Bleha, J A (jessica.bleha@umontana.edu) , Geosciences Department University of
Montana - Missoula, 32 Campus Drive #1296, Missoula, MT 59812, United States
Harper, J T (joel.harper@umontana.edu) , Geosciences Department University of
Montana - Missoula, 32 Campus Drive #1296, Missoula, MT 59812, United States
In the mountain west the timing of the spring snowmelt pulse has considerable impact on
water resources and ecological processes such as fire. A forward shift of this timing due
to warming climate has received considerable attention. The internal structure and
physical processes of the mountain snowpack also have a large influence on the timing of
spring runoff. Here we investigate controlling factors in the timing of the spring melt
pulse in a large-scale northern Rockies watershed. We employ a snowmelt model to
investigate historical records of the initiation of spring snowmelt runoff. Two watersheds
were selected as test sites: (1) St. Mary â€â€œ a small (81 km2) basin east
of the continental divide and (2) Middle Fork Flathead River â€â€œ a
large (2903 km2) basin west of the divide. Moderate Resolution Imaging
Spectroradiometer (MODIS) 8-day snow-cover products, Snowpack Telemetry
(SNOTEL), climate, and streamflow data were collected for the study area for years
2000-2005. We performed a detailed accuracy assessment of the snow-cover product in
the mountainous terrain and poor weather conditions of the northern Rockies. The
assessment utilized 6 SNOTEL sites and over 1000 ground based measurements spanning
the 6 year period. The MODIS products were then used to determine snow covered area
within the test basins at 8 day time steps throughout the six winter seasons. Snow-cover
and climate data were input to the spatially distributed snowmelt model to determine the
component of runoff derived from snow. The time series of modeled snowmelt was
compared to basin runoff records to elucidate the processes governing the initial signal of
spring snowmelt in river discharge.
C33C-1300
Monitoring and Modelling Glacier Melt and Runoff on Juncal Norte Glacier, Aconcagua
River Basin, Central Chile
* Pellicciotti, F (pellicciotti@ifu.baug.ethz.ch) , Institute of Environmental Engineering,
Swiss Federal Institute of Technology (ETH), Zurich, Wolfgang Pauli Strasse 15, IfUHIL, ETH Hoenggerberg, Zurich, 8093 Switzerland
Helbing, J F (helbing@vaw.baug.ethz.ch) , Laboratory of Hydraulics, Hydrology and
Glaciology, Swiss Federal Institute of Technology (ETH), Zurich, Gloriastrasse 37-39,
ETH Zentrum, Zurich, 8092 Switzerland
Araos, J (jose.araos@gmail.com) , Grupo Glaciologia y Geoscencias, CEQUA, Avenida
Bulnes 01890,, Punta Arenas, 6200000 Chile
Favier, V (vifavier@gmail.com) , Centro de Estudios Avanzados en Zonas Aridas,
Casilla 599, Benavente 980, La Serena, 1700000 Chile
Rivera, A (arivera@cecs.cl) , Centro de Estudios Cientificos, Maipu 60, Valdivia,
5090000 Chile
Corripio, J (corripio@ifu.baug.ethz.ch) , Institute of Environmental Engineering, Swiss
Federal Institute of Technology (ETH), Zurich, Wolfgang Pauli Strasse 15, IfU- HIL,
ETH Hoenggerberg, Zurich, 8093 Switzerland
Sicart, J M (sicart@msem.univ-montp2.fr) , Great Ice- IRD, Case MSE, UMII, 300,
avenue du Professeur Emile Jeanbrau, cedex 5, Montpellier, 34095 France
Results from a recent glacio-meteorological experiment on the Juncal Norte glacier, in
central Chile, are presented. Melt water is a crucial resource in the Central Andes, as it
provides drinking water, water for agriculture and for industrial uses. There is also
increasing competition for water use and allocation, as water demands from mining and
industry are rising. Assessing water availability in this region and its relation with
climatic variations is therefore crucial. The Dry Central Andes are characterised by a
climatic setting different from that of the Alps and the subtropical Andes of Bolivia and
Peru. Summers are very dry and stable, with precipitation close to zero and low relative
humidity. Solar radiation is very intense, and plays a key role in the energy balance of
snow covers and glaciers. The main aim of this study is to investigate the glacier-climate
interaction in this area, with particular attention devoted to advanced modelling
techniques for the spatial redistribution of meteorological variables, in order to gain an
accurate picture of the ablation processes typical of these latitudes. During the ablation
season 2005/2006, an extensive field campaign was conducted on the Juncal Norte
glacier, aimed at monitoring the melt and runoff generation processes on this remote
glacier in the dry Andes. Melt rates, runoff at the snout, meteorological variables over
and near the glacier, GPS data and glacier topography were recorded over the entire
ablation season. Using this extensive and accurate data set, the spatial and temporal
variability of the meteorological variables that drive the melt process on the glacier is
investigated, together with the process of runoff generation. An energy balance model is
used to simulate melt across the glacier, and special attention is devoted to the modelling
of the solar radiation energy flux. The components of the energy balance are compared
with those of Alpine basins. The validity of parameterisations of the meteorological input
variables that were developed in the Alps (such as albedo and cloud cover) is
investigated, together with the extrapolation of temperature from point measurements.
More advanced extrapolation techniques for air temperature are used in contrast to
constant lapse rates. In contrast to alpine glaciers, data scarcity in this region is a strong
limiting factor for modelling glacier melt and runoff. In particular, redistribution of
meteorological variables that are input to melt models and knowledge of the initial snow
water equivalent across the basin is difficult. These issues are also addressed in the paper.
C33C-1301
Ice, Cloud, and land Elevation (ICESat) satellite Data Management and Delivery at the
National Snow and Ice Data Center
Fowler, D (dfowler@nsidc.org) , National Snow and Ice Data Center, CIRES University
of Colorado, Boulder UCB 449, Boulder, CO 80309
* Korn, D (dkorn@nsidc.org) , National Snow and Ice Data Center, CIRES University of
Colorado, Boulder UCB 449, Boulder, CO 80309
The Geoscience Laser Altimeter System (GLAS) instrument aboard the Ice, Cloud, and
land Elevation (ICESat) satellite launched on 12 January 2003. The primary objective of
the ICESat mission is to provide global measurements of polar ice sheet elevation to
discern changes in ice volume (mass balance) over time. Secondary objectives of the
mission are to measure sea ice roughness and thickness, cloud and atmospheric
properties, land topography, vegetation canopy heights, ocean surface topography, and
surface reflectivity. The GLAS instrument has three lasers, each of which has a 1064 nm
laser channel for surface altimetry and dense cloud heights, and a 532 nm lidar channel
for the vertical distribution of clouds and aerosols. Here, we present a description of the
data flow through NASA's EOSDIS Core System (ECS) and how users gain access to the
data. National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder
is the primary ECS center for archiving and distributing GLAS data to researchers. To
fulfill the above objectives, GLAS data can be requested in a variety of methods
including an online Data Pool, several search and order tools, and a spatial subsetting
option. This poster will describe these methods. Multiple releases of the ICESat/GLAS
data are now available at NSIDC (http://nsidc.org/data/icesat/).
C33C-1302
Distributed modelling of melting on Antizana Glacier 15, Ecuador
Wagnon, P (patrick@lgge.obs.ujf-grenoble.fr) , UR Great-Ice, IRD-LGGE, 54 rue
Molière, BP 96, Saint Martin D'heres, 38402 France
* Favier, V (vincent.favier@ceaza.cl) , CEAZA, casilla 599, Benavente 980, La Serena, 1
700 000 Chile
* Favier, V (vincent.favier@ceaza.cl) , UR Great-Ice, IRD, Maison des Sciences de
l’Eau, BP 64501, Montpellier, 34394 France
Corripio G., J (corripio@ifu.baug.ethz.ch) , ETH - Zurich, CH-8093, Zurich, s/n
Switzerland
The surface energy balance of Ecuador's glaciers is particularly sensitive to their surface
albedo whose variations are closely linked to solid precipitation occurrence. In order to
assess distributed albedo values at the glacier scale, an automatic digital camera was
installed on the frontal moraine of Antizana Glacier 15. The images from this camera
were processed to obtain the relative variation of albedo. Over the period March 15, 2002
� April 1, 2003, a distributed surface energy balance model was applied using as input
the meteorological dataset recollected locally at the glacier surface and the albedo maps.
Despite the restricted number of good quality photographs due to the important
cloudiness at the study site, the model allows accurate computations of the monthly
ablation and of the annual specific mass balance. Simulations show that gradients of
ablation with altitude are mostly explained by albedo variations. Over the ablation area
the computed ablation agrees fairly well with the field measurements. However, in the
accumulation area, computed turbulent heat fluxes are overestimated and are responsible
for a large difference between computed and observed ablation. Finally the model is
simplified to a 1-D model taking into account only the albedo and temperature lapse rate
with altitude. This operational model is successfully tested over the 1995-2005 period.
C33C-1303
The energy balance on the surface of a tropical glacier tongue. Investigations on glacier
Artesonraju, Cordillera Blanca, Per\'{u}.
* Juen, I (irmgard.juen@uibk.ac.at) , Tropical Glaciology Group, Innrain 52, Innsbruck,
6020 Austria
M\"{o}lg, T (thomas.moelg@uibk.ac.at) , Tropical Glaciology Group, Innrain 52,
Innsbruck, 6020 Austria
Wagnon, P (Patrick.Wagnon@lgge.obs.ujf-grenoble.fr) , IRD-LGGE, St Martin d'Heres
Cedex BP 96, Grenoble, 38402 France
Cullen, N J (nicolas.cullen@uibk.ac.at) , Tropical Glaciology Group, Innrain 52,
Innsbruck, 6020 Austria
Kaser, G (georg.kaser@uibk.ac.at) , Tropical Glaciology Group, Innrain 52, Innsbruck,
6020 Austria
The Cordillera Blanca in Per\'{u} is situated in the Outer Tropics spanning from 8 to 10
\deg South. Solar incidence and air temperature show only minor seasonal variations
whereas precipitation occurs mainly from October to April. An energy balance station
was installed on the tongue of glacier Artesonraju (4850 m a.s.l.) in March 2004. In this
study each component of the energy balance on the glacier surface is analysed separately
over a full year, covering one dry and one wet season. During the dry season glacier melt
at the glacier tongue is app. 0.5 m we per month. In the wet season glacier melt is twice
as much with 1 m we per month. This is due to higher energy fluxes and decreased
sublimation during the wet season. With an energy balance model that has already been
proved under tropical climate conditions (M\"{o}lg and Hardy, 2004) each energy flux is
changed individually to evaluate the change in the amount of glacier melt. First results
indicate that a change in humidity related variables affects glacier melt very differently in
the dry and wet season, whereas a change in air temperature changes glacier melt more
constantly throughout the year.
C33C-1304
Climate Change and Glacier Retreat in Irian Jaya Over the Past Half Century
* Kincaid, J L (jkincaid@geog.tamu.edu) , Texas A&M University, MS 3147
Department of Geography Texas A&M University, College Station, Tx 77843-3147,
United States
Klein, A G (klein@geog.tamu.edu) , Texas A&M University, MS 3147 Department of
Geography Texas A&M University, College Station, Tx 77843-3147, United States
Over the past century, glaciers throughout the tropics have predominately retreated.
These small glaciers, which respond quickly to climate changes, are becoming
increasingly important in understanding glacier-climate interactions. The glaciers on Mt.
Jaya in Irian Jaya, Indonesia, are the last remaining tropical glaciers in the Western
Pacific region. Rates of ice loss, calculated from area measurements for the Mt. Jaya
glaciers in 1942, 1972, 1987, and 2005, indicate that ice loss on Mt. Jaya has increased
during each subsequent period. Preliminary modeling using 600 hPa atmospheric
temperature, specific humidity, wind speeds, and surface precipitation and radiation
fields, acquired from the NCEP Reanalysis dataset, indicates that the only climate
variable having a statistically-significant change with a magnitude great enough to
strongly affect ice loss on these glaciers was an increase in atmospheric temperature of
0.24 \�C between 1972 and 1987. However, accelerated ice loss occurring from 19882005 without large observed changes in climate indicates that a more complex
explanation may be required. Small, though statistically-significant changes were found
in regional precipitation with precipitation decreasing from 1972-1987 and increasing
from 1988-2005. While these changes were not of sufficient magnitude to have greatly
affected ice loss on these glaciers, increased precipitation along with a rising freezing
level may have resulted in a greater proportion of the glacier surface being affected by
rain. This may account for the increased recession rate observed in the latter period.
Spatial variation in incoming shortwave radiation may also control the observed pattern
of retreat. Further analysis of climate variations over each observational period will be
completed. Modeling of the shortwave radiation field over these glaciers should shed
additional light on the factors controlling Mt. Jaya glacier retreat.
C33C-1305
Climate during the Last Glacial Maximum in the Wasatch Mountains Inferred from
Glacier Mass-Balance and Ice-Flow Modeling
* Bash, E A (ebash@gustavus.edu) , Gustavus Adolphus College, Geology Department
800 W. College Ave., Saint Peter, MN 56082, United States
Laabs, B J (blaabs@gustavus.edu) , Gustavus Adolphus College, Geology Department
800 W. College Ave., Saint Peter, MN 56082, United States
The Wasatch Mountains of northern Utah contained numerous valley glaciers east and
immediately downwind of Lake Bonneville during the Last Glacial Maximum (LGM).
While the extent and chronology of glaciation in the Wasatch Mountains and the rise and
fall of Lake Bonneville are becoming increasingly well understood, inferences of climatic
conditions during the LGM for this area and elsewhere in the Rocky Mountains and
northern Great Basin have yielded a wide range of temperature depression estimates. For
example, previous estimates of temperature depression based on glacier and lake
reconstructions in this region generally range from $7\deg$ to $9\deg$ C colder than
modern. Glacier modeling studies for Little Cottonwood Canyon (northern Wasatch
Mountains) suggest that such temperature depressions would have been accompanied by
precipitation increases of about 3 to 1x modern, respectively (McCoy and Williams,
1985; Laabs et al., 2006). However, interpretations of other proxies suggest that
temperature depression in this area may have been significantly greater, up to $13\deg$ C
(e.g., Kaufman 2003), which would likely have been accompanied by less precipitation
than modern. To address this issue, we reconstructed ice extent in the American Fork
Canyon of the Wasatch Mountains and applied glacier modeling methods of Plummer
and Phillips (2003) to infer climatic conditions during the LGM. Field mapping indicates
that glaciers occupied an area of more than 20 km$^{2}$ in the canyon and reached
maximum lengths of about 9 km. To link ice extent to climatic changes, a physically
based, two-dimensional numerical model of glacier mass balance and ice flow was
applied to these valleys. The modeling approach allows the combined effects of
temperature, precipitation and solar radiation on net mass balance of a drainage basin to
be explored. Results of model experiments indicate that a temperature depression of less
than $9\deg$ C in the American Fork Canyon would have been accompanied by greater
precipitation than modern, whereas greater temperature depressions would have required
less-than-modern precipitation to sustain glaciers in the Wasatch Mountains. Without
independent estimates of either temperature or precipitation for the LGM, model results
do not provide a unique combination of these two variables based on simulated ice
extent. However, the reconstructed pattern of glaciation in the Wasatch and Uinta
Mountains indicates a sharp westward decline in glacier equilibrium-line altitudes in
valleys immediately downwind of Lake Bonneville (Munroe et al, 2006), which suggests
that precipitation in the Wasatch Mountains was enhanced during the LGM. Therefore,
model results can be used to set limits on the temperature and precipitation. We estimate
that, if temperatures during the LGM were $6\deg$ to $8\deg$ C less than modern,
precipitation was 3 to 1.5x modern. Such precipitation increases would reflect the
importance of Lake Bonneville as a moisture source for valleys in the Wasatch
Mountains, as suggested by previous studies.
Authors (2006), Title, Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract xxxxx-xx