AMERICAN GEOPHYSICAL UNION ANNUAL MEETING, DEC 13-17,
2004, SAN FRANCISCO, CA
Union [U] Session: Climate Challenges to Mountain Water Resources & Ecosystems
U51A MCC:3006 Friday 0800h
Challenges to Mountain Water Resources and Ecosystems I
Presiding:C Millar, PSW Research Station, USDA Forest Service; D Fagre, U.S. Geological Survey
Science Center; D Cayan, U.S. Geological Survey, Scripps Institution of Oceanography
U51A-01 INVITED 08:00h
Integrating Climate and Ecosystem-Response Sciences in Temperate Western North American
Mountains: The CIRMOUNT Initiative
* Millar, C I (cmillar@fs.fed.us) , USDA Forest Service, PSW Research Station, P.O. Box 245, Berkeley,
CA 94701 United States
Fagre, D B (dan_fagre@usgs.gov) , USGS Science Center, Glacier National Park, West Glacier, MT
59936 United States
Mountain regions are uniquely sensitive to changes in climate, vulnerable to climate effects on biotic and
physical factors of intense social concern, and serve as critical early-warning systems of climate impacts.
Escalating demands on western North American (WNA) mountain ecosystems increasingly stress both
natural resources and rural community capacities; changes in mountain systems cascade to issues of
national concern. Although WNA has long been a focus for climate- and climate-related environmental
research, these efforts remain disciplinary and poorly integrated, hindering interpretation into policy and
management. Knowledge is further hampered by lack of standardized climate monitoring stations at highelevations in WNA. An initiative is emerging as the Consortium for Integrated Climate Research in
Western Mountains (CIRMOUNT) whose primary goal is to improve knowledge of high-elevation
climate systems and to better integrate physical, ecological, and social sciences relevant to climate
change, ecosystem response, and natural-resource policy in WNA. CIRMOUNT seeks to focus research
on climate variability and ecosystem response (progress in understanding synoptic scale processes) that
improves interpretation of linkages between ecosystem functions and human processing (progress in
understanding human-environment integration), which in turn would yield applicable information and
understanding on key societal issues such as mountains as water towers, biodiversity, carbon forest sinks,
and wildland hazards such as fire and forest dieback (progress in understanding ecosystem services and
key thresholds). Achieving such integration depends first on implementing a network of high-elevation
climate-monitoring stations, and linking these with integrated ecosystem-response studies. Achievements
since 2003 include convening the 2004 Mountain Climate Sciences Symposium (1, 2) and several special
sessions at technical conferences; initiating a biennial mountain climate research symposium
(MTNCLIM), the first to be held in spring 2005; developing a strategy for climate-monitoring in WNA;
installing and networking high-elevation (>3000m) climate-monitoring stations; and completing three
target regions (Glacier National Park, MT; Sierra Nevada and White Mountains, CA) of the international
GLORIA (Global Observation Research Initiative in Alpine Environments) plant-monitoring project, the
first in WNA. CIRMOUNT emphasizes integration at the regional scale in WNA, collaborating with and
complementing projects such as the Western Mountain Initiative, whose mandate is more targeted than
2
CIRMOUNT's, and global programs such as GLORIA and the international Mountain Research Initiative.
Achievement of continuing success in WNA hinges on the capacity to secure long-term funding and
institutional investment. (1) See associated URL for paper and poster pdfs (2) Discussing the future of
western U.S. mountains, climate change, and ecosystems. EOS 31 August 2004, 85(35), p. 329
<a href='http://www.fs.fes.us/psw/mcss' >http://www.fs.fes.us/psw/mcss
U51A-02 08:15h
A High Elevation Climate Monitoring Network: Strategy and Progress
* Redmond, K T (kelly.redmond@dri.edu) , Desert Research Institute / Western Regional Climate Center,
2215 Raggio Parkway, Reno, NV 89512-1095 United States
Populations living at low elevations are critically dependent on processes and resources at higher
elevations. Most western U.S. streamflow begins as mountain snowmelt. Observational evidence and
theoretical considerations indicate that climate variations in a given geographic domain can and do exhibit
different characteristics and temporal behavior at different elevations. Subtleties in the interplay between
topography and airflow can significantly affect precipitation patterns. However, there are very few
systematic, long-term, in-situ, climate quality, high-altitude observational time series with hourly
resolution for the western North American mountains to investigate these issues at the proper scales.
Climate at high elevations is severely undersampled, a consequence of the harsh physical environment,
and demands on sensors, maintenance, access, communications, time, and budgets. Costs are higher,
human presence is limited, AC power is often not available, and there are permitting and aesthetic
constraints. The observational strategy should include these main elements: 1) All major mountain ranges
should be sampled. 2) Along-axis and cross-axis sampling for major mountain chains. 3) Approximately
5-10 sites per state (1 per 56000 sq km to 1 per 28000 sq km). 4) Highest sites as high as possible within
each state, but at both high relative and absolute elevations. 5) Free air exposures at higher sites. 6)
Utilize existing measurements and networks, and extend existing records, when possible. 7) AC power to
prevent ice/rime when practical. 8) Temperature, relative humidity, wind speed and direction, solar
radiation as main elements, others as feasible. 9) Hourly readings, and real time communication whenever
possible. 10) Absence of local artificial influences, site stable for next 5-10 decades. 11) Current and
historical measurements accessible via World Wide Web when possible. 12) Hydro measurements
(precipitation, snow water content and depth) are not practical at highest points, so have lower sites in
more protected settings to permit these. Maintain stable site characteristics (e.g., vegetation height)
needed for measurement homogeneity. 13) High quality, rugged, durable instrumentation with proven
track records greatly desirable. 14) Site documentation history available and accessible.
U51A-03 INVITED 08:30h
Climate-Change Uncertainties and Water Supplies from Western Mountains--What are
Observations and Models Trying to tell us?
* Dettinger, M (mddettin@usgs.gov) , U.S. Geological Survey, Scripps Institution of Oceanography, UC
San Diego, Dept 0224 9500 Gilman Drive, La Jolla, CA 92093 United States
Cayan, D (dcayan@ucsd.edu) , U.S. Geological Survey, Scripps Institution of Oceanography, UC San
Diego, Dept 0224 9500 Gilman Drive, La Jolla, CA 92093 United States
Stewart, I (iris@pangea.stanford.edu) , Scripps Institution of Oceanography, UC San Diego, Dept 0224
9500 Gilman Drive, La Jolla, CA 92093 United States
3
Knowles, N (noah_k@earthlink.net) , U.S. Geological Survey, 345 Middlefield Road, MS496, Menlo
Park, CA 94025 United States
In recent decades, snowmelt and streamflow timing in the river basins of the mountains of western North
America have changed in response to warmer winters and springs. The observed hydrological trends
toward smaller snowpacks and earlier runoff are widespread and significant. Although these trends
partially reflect natural interdecadal regimes of the Pacific-North American climate system, a large
component of the recent changes can be attributed to even broader global-warming trends. The future of
these temperature, snowpack, and streamflow trends in the mountainous West are uncertain and some of
the key uncertainties at this regional scale are unlikely to be eliminated soon. Nonetheless, long-term
resource-management planning will need to consider the likely hydrologic changes soon because
important long-term plans are being made in many settings and because the changes are already
underway. To date, climate-change uncertainties typically have been addressed by projecting the impacts
of one or two climate-change projections, chosen based on availability or to capture the extremes among
available projections. However, characterizing the overall statistical distributions of changes in a
moderately large projection ensemble provides new insights into the projections: (i) uncertainties
associated with future emissions are comparable with the uncertainties due to model differences, so that
neither source of uncertainties should be neglected or underrepresented; (ii) projections of 21st Century
temperatures are broadly in consensus but spread and change more overall than do future-precipitation
scenarios, so that performance of water-resource systems under near-term temperature changes is
particularly pressing; (iii) projections of extremely wet futures for the West are statistical outliers among
current projections; and (iv) the current projections that are warmest tend, overall, to yield a moderately
drier California, while the cooler projections yield a somewhat wetter future. These findings should be
considered in plans and assumptions about future observational systems, snowpack and streamflow, and
water supplies in western mountains.
U51A-04 08:45h
Mountain Hydrology of the Semi-Arid Western U.S.: Research Needs, Opportunities and
Challenges
* Bales, R (rbales@ucmerced.edu) , University of California, School of Engineering, Merced, 95344
Dozier, J , University of California, Bren School, Santa Barbara, 93106
Molotch, N , University of Colorado, CIRES, Boulder, 80309
Painter, T , University of Colorado, NSIDC, Boulder, 80309
Rice, R , University of California, School of Engineering, Merced, 95344
In the semi-arid Western U.S., water resources are being stressed by the combination of climate warming,
changing land use, and population growth. Multiple consensus planning documents point to this region as
perhaps the highest priority for new hydrologic understanding. Three main hydrologic issues illustrate
research needs in the snow-driven hydrology of the region. First, despite the hydrologic importance of
mountainous regions, the processes controlling their energy, water and biogeochemical fluxes are not well
understood. Second, there exists a need to realize, at various spatial and temporal scales, the feedback
systems between hydrological fluxes and biogeochemical and ecological processes. Third, the paucity of
adequate observation networks in mountainous regions hampers improvements in understanding these
processes. For example, we lack an adequate description of factors controlling the partitioning of
snowmelt into runoff versus infiltration and evapotranspiration, and need strategies to accurately measure
the variability of precipitation, snow cover and soil moisture. The amount of mountain-block and
mountain-front recharge and how recharge patterns respond to climate variability are poorly known
across the mountainous West. Moreover, hydrologic modelers and those measuring important hydrologic
4
variables from remote sensing and distributed in situ sites have failed to bridge rifts between modeling
needs and available measurements. Research and operational communities will benefit from data
fusion/integration, improved measurement arrays, and rapid data access. For example, the hydrologic
modeling community would advance if given new access to single rather than disparate sources of
bundles of cutting-edge remote sensing retrievals of snow covered area and albedo, in situ measurements
of snow water equivalent and precipitation, and spatio-temporal fields of variables that drive models. In
addition, opportunities exist for the deployment of new technologies, taking advantage of research in
spatially distributed sensor networks that can enhance data recovery and analysis.
<a href='http://ucmeng.net/snri/snho' >http://ucmeng.net/snri/snho
U51A-05 09:00h
Influences of Climate Trends on Snowpack and Wildfire in the West
* Mote, P W (philip@atmos.washington.edu) , JISAO Climate Impacts Group, Box 354235 University of
Washington, Seattle, WA 98195 United States
Hamlet, A F (hamleaf@u.washington.edu) , JISAO Climate Impacts Group, Box 354235 University of
Washington, Seattle, WA 98195 United States
Hamlet, A F (hamleaf@u.washington.edu) , Dept of Civil and Environmental Engineering, Box 352700
University of Washington, Seattle, WA 98195 United States
Gedalof, Z (zgedalof@uoguelph.ca) , Dept of Geography, University of Guelph, Guelph, ON N1G 2W1
Canada
A comprehensive picture of change in the Western U.S. is emerging from the work of several research
groups: spring snowpack amounts have declined, peak snowmelt-driven streamflow has drifted earlier in
the spring, winter flows have increased and summer flows have decreased. Recent years have also seen
very large wildfires, which cannot be explained simply as the latent effect of decades of fire suppression.
Using modeling and statistical analysis of observations, we (1) show how patterns of variability and
change in both snowpack and wildfire are related to climate variables, (2) provide indications of how
these trends will unfold in the future, and (3) discuss implications for managing water and ecological
resources in the West.
U51A-06 09:15h
Glacier Shrinkage and Effects on Alpine Hydrology
Basagic, H (basagic@pdx.edu) , Departments of Geology and Geography Portland State University, 1721
SW Broadway, Portland, OR 97207 United States
* Fountain, A G (andrew@pdx.edu) , Departments of Geology and Geography Portland State University,
1721 SW Broadway, Portland, OR 97207 United States
Clark, D H (doug.clark@wwu.edu) , Geology Department Western Washington University, 516 High
Street, Bellingham, WA 98225 United States
Alpine glaciers cover an area of about 553 km$^{2}$ in seven western states of the American West. With
few exceptions, all glaciers have been shrinking over the past century and the rate of shrinkage has
accelerated over the past few decades. Overall, smaller glaciers exhibit greatest shrinkage, relative to their
size, compared to larger glaciers. Preliminary results from studies of glacier change in several national
parks reveal the spatial pattern of glacier change. Glacier shrinkage, while contributing to global sea level
change, has two important local effects. First, the net release of water from its storage in the frozen state
5
enhances overall stream discharge. Second, the shrinking area of glaciers reduces their moderating effect
on stream flow, particularly during late-summer and drought periods, and shifts peak runoff towards early
summer. Consequently these alpine basins become more susceptible to future drought. In addition to
these "clean" glaciers, debris-covered glaciers are probably important as well. Debris-covered glaciers
melt at much slower rates than adjacent "clean" glaciers, with reduced daily variations in melt because of
the insulation provided by the surface debris layer. The number and extent of debris-covered glaciers in
the American west is not well known therefore their hydrological contribution is uncertain. However, if
the number of debris-covered glaciers can be scaled from an inventory of those in the Rocky Mountain
National Park (Achuff, 2003), the volume of debris-covered ice may be considerable. From an ecological
perspective, the greatest effects are in the high alpine regions where glacier recession opens new areas for
biological expansion, and where the hydrological dependence on glaciers is greatest. Lesser effects,
related to suspended sediment loads, are felt well downstream (10's km) from glaciers.
U51A-07 09:30h
Climate and Wildfire in Mountains of the Western United States
Alfaro, E (ealfarom@ucsd.edu) , School of Physics, University of Costa Rica, 2060 Ciud. Rodrigo Facio,
San Jose, 1000 Costa Rica
Alfaro, E (ealfarom@ucsd.edu) , Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA
92093-0224 United States
* Westerling, A L (leroy@ucsd.edu) , Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla,
CA 92093-0224 United States
Cayan, D R (dcayan@ucsd.edu) , Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA
92093-0224 United States
Cayan, D R (dcayan@ucsd.edu) , U. S. Geological Survey, 9500 Gilman Drive, La Jolla, CA 92093-0224
United States
Since the mid-1980s, there has been a dramatic increase in the area burned in wildfires in mountain
forests of the western United States, with mean annual area burned nearly three and a half times higher
compared to the preceding one and a half decades.(1) Concomitant increases in variability in annual area
burned and in fire suppression costs pose a serious challenge for land management in the mountainous
West. The variance in annual area burned since 1987 is nineteen times its previous level. Since managers
must be prepared for the worst possible scenarios in every fire season, increased uncertainty about the
scale of the western fire season each year imposes high costs on public agencies. Annual real suppression
costs in western forests have more than doubled for the Forest Service since 1987, while the variance in
annual suppression costs is over four times higher. Although federal agencies' fire suppression budgets
have increased recently, they are still close to what would be spent in an "average" year that seldom
occurs, while costs tend to fluctuate between low and high extremes. Modeling area burned and
suppression costs as a function of climate variability alone, Westerling (2004, unpublished work) found
that the probability of the Forest Service's suppression expenses exceeding the current annual suppression
budget has exceeded 50% since 1987, a substantial increase from the one-in-three chance over the
preceding 40 years. Recent progress in our understanding of the links between climate and wildfire, and
in our ability to forecast some aspects of both climate and wildfire season severity a season or more in
advance, offers some hope that these costs might be ameliorated through the integration of climate
information into fire and fuels management. In addition to the effects of climate variability on wildfire,
long-term biomass accumulations in some western ecosystems have fueled an increasing incidence of
large, stand-replacing wildfires where such fires were previously rare. These severe large fires can result
in erosion and changes in vegetation type, with consequences for water quality, stream flow, future
biological productivity of the affected areas, and habitat loss for endangered species. Apart from their
6
deleterious ecological consequences, severe fires can also dramatically affect amenity values for public
lands and for homeowners living in the wildland-urban interface. In the National Fire Plan, land
management agencies have committed to reducing fuels on millions of hectares of public lands. The
primary means are mechanical removal, prescribed fire and wildland fire use. The Forest Service
estimates they will need to spend hundreds of millions of dollars per year to meet their fuel reduction
targets, while efforts in recent years have not kept up with the current rate of biomass increase. Use of
climate information for targeting resources and scheduling prescribed burns could increase the efficiency
of these efforts. In this study we review the fire history since 1970 for western mountain forests, and
demonstrate apparent links between regional climate variability and decadal-scale changes in annual area
burned. This analysis explores how wildfire size and frequency have varied over the past thirty-five years
by elevation and latitude, and how climate indices such as precipitation, temperature, drought indices and
the timing of spring runoff vary in importance for fire season severity by elevation in forests around the
western United States.
U51A-08 09:45h
Antecedent Precipitation Trumps Drought in Causing Southeast Arizona Wildfires
* Comrie, A C (comrie@arizona.edu) , University of Arizona, Dept of Geography 409 Harvill Bldg,
Tucson, AZ 85721-0076 United States
Crimmins, M A (crimmins@email.arizona.edu) , University of Arizona, Dept of Geography 409 Harvill
Bldg, Tucson, AZ 85721-0076 United States
Long-term antecedent climate conditions are often overlooked as important drivers of wildfire variability.
Fuel moisture levels and fine-fuel productivity are controlled by variability in precipitation and
temperature at long timescales (months to years) prior to wildfire events. This study examines
relationships between wildfire statistics (total area burned and total number of fires) aggregated for
southeastern Arizona and antecedent climate conditions relative to 29 fire seasons (April-May-June)
between 1973 and 2001. High and low elevation fires were examined separately to determine the
influence of climate variability on dominant fuel types (low elevation grasslands with fine fuels vs. high
elevation forests with heavy fuels). Positive correlations between lagged precipitation and total area
burned highlight the importance of climate in regulating fine fuel production for both high and low
elevation fires. Surprisingly, no significant negative correlations between precipitation and seasonal
wildfire statistics were found at any seasonal lag. Drought conditions were not associated with higher area
burned or a greater number of fires. Larger low elevation fires were actually associated with wet
antecedent conditions until just prior to the fire season. Larger high elevation fires were associated with
wet conditions during seasons up to three years prior to the fire season.
Author(s) (2004), Title, Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract #####-##.
Union [U]
U52A MCC:3006 Friday 1020h
Challenges to Mountain Water Resources and Ecosystems II
Presiding:D Cayan, Scripps Institution of Oceanography; C Millar, PSW Research Station, USDA Forest
Service; D Fagre, U.S. Geological Survey Science Center
7
U52A-01 10:20h
Fire Regimes and Forest Structure in the Mountains of Northwestern Mexico and Southern
California
* Stephens, S L (stephens@nature.berkeley.edu) , Department of Environmental Sciecne, Policy, and
Management, 151 Hilgard Hall UC Berkeley, Berkeley, CA 94720 United States
In contrast to a few isolated forests in northern Mexico, most forests in the western Untied States have
been significantly modified by fire suppression, harvesting, and livestock grazing. The culmination of
these past management activities has produced over 20 million ha of US forests with high fire hazards and
many of these areas are in need of restoration. Understanding reference conditions is challenging because
we have few intact forests functioning under the continuing influence of climate variation, insects,
diseases, and frequent fires. This presentation summarizes information from reference sites in
northwestern Mexico and contrasts it to current forest structure and fire regimes in southern California
forests. Heterogeneity is common in the intact forests of northwestern Mexico. Restoration targets across
similar forests in the United States and elsewhere should incorporate variation and not manage for
average characteristics at the stand level, replicated for all stands across very large spatial scales.
Conservation of the forests in the northwester Mexico is critical because it is the last landscape-scale, oldgrowth mixed conifer forest in western North America with a relatively intact frequent fire regime.
U52A-02 10:35h
Sensitivity of Southwestern US Mountain Ecosystems to Climate Variability: Interactions Among
Forest Dieback, Fire, and Erosion
* Allen, C D (craig_allen@usgs.gov) , USGS Jemez Mts Field Station, HCR 1, Box 1, No. 17, Los
Alamos, NM 87544 United States
Millions of hectares in the upland landscapes of the Southwestern United States have been affected by
forest dieback and severe fire activity since the late 1990s, a period of ongoing severe drought and
unusual warmth. Climate regulates physiological plant stress that can directly cause vegetation mortality,
and also influences associated insect outbreak dynamics. Climate also interacts with fuel conditions to
drive regional fire activity. Current and historic patterns of forest dieback, fire activity, and erosion are
described across landscape gradients in Southwestern mountains, particularly the Jemez Mountains of
New Mexico. Methods used include inventory and dating of live and dead woody plants to assess
demographic changes through time, long-term (since 1991) measurements of ponderosa pine tree-growth
at three sites with dendrometer bands, monitoring of herbaceous vegetation along 3 km of permanent
transects since 1991, aerial photograph analyses of insect outbreaks and forest dieback and fire activity,
and hydrological measurements of runoff and erosion. Similarities and differences in vegetation dieback
and regional fire activity patterns between the current drought and the 1950s (when regional drought last
affected the Southwest) are explained by changes in climatic and vegetation conditions. The current
climate-induced vegetation dieback and pulse of regional fire activity have strong feedbacks with various
key ecosystem processes, including water budgets and soil erosion. For example, severe drought and fire
both markedly reduce the surface cover of live plants and dead plant materials ("litter"), triggering
nonlinear increases in erosion rates once the connectivity of bare soil patches exceeds critical threshold
values, particularly during high-intensity summer rainfall events that characterize the Southwestern
summer "monsoon". These observations highlight the magnitude, rapidity, and complexity of climateinduced disturbance processes, and provide an analog for potential nonlinear impacts of climate change to
mountain ecosystems.
8
U52A-03 10:50h
Climate Change Altered Disturbance Regimes in High Elevation Pine Ecosystems
* Logan, J A (jalogan@fs.fed.us) , USDA Forest Service, 860 N 1200 East, Logan, UT 84321
Insects in aggregate are the greatest cause of forest disturbance. Outbreaks of both native and exotic
insects can be spectacular events in both their intensity and spatial extent. In the case of native species,
forest ecosystems have co-evolved (or at least co-adapted) in ways that incorporate these disturbances
into the normal cycle of forest maturation and renewal. The time frame of response to changing climate,
however, is much shorter for insects (typically one year) than for their host forests (decades or longer). As
a result, outbreaks of forest insects, particularly bark beetles, are occurring at unprecedented levels
throughout western North America, resulting in the loss of biodiversity and potentially entire ecosystems.
In this talk, I will describe one such ecosystem, the whitebark pine association at high elevations in the
north-central Rocky Mountains of the United States. White bark pines are keystone species, which in
consort with Clark's nutcracker, build entire ecosystems at high elevations. These ecosystems provide
valuable ecological services, including the distribution and abundance of water resources. I will briefly
describe the keystone nature of whitebark pine and the historic role of mountain pine beetle disturbance in
these ecosystems. The mountain pine beetle is the most important outbreak insect in forests of the western
United States. Although capable of spectacular outbreak events, in historic climate regimes, outbreak
populations were largely restricted to lower elevation pines; for example, lodgepole and ponderosa pines.
The recent series of unusually warm years, however, has allowed this insect to expand its range into high
elevation, whitebark pine ecosystems with devastating consequences. The aspects of mountain pine beetle
thermal ecology that has allowed it to capitalize so effectively on a warming climate will be discussed. A
model that incorporates critical thermal attributes of the mountain pine beetle's life cycle was constructed
and used to predict the consequences of a changing climate under the 1990 IPCC "business as usual"
scenario. Based on results from these simulations, sophisticated, high-resolution weather monitoring
stations were established at a high elevation site in the summer of 1995 (Railroad Ridge, White Cloud
Mountains, Central Idaho at an elevation of 10,000 ft.). Recently (summer 2003), the first trees were
attacked on Rail Road Ridge. The outbreak has progressed at a truly astounding rate. The reasons for the
unusually rapid progression of this outbreak event will be considered, as will the potential consequences
of mortality that is occurring across the entire U.S. range of whitebark pine. Finally, I will discuss both
the challenges to, and the potential for, formulating effective management responses.
<a href='http://www.usu.edu/beetle' >http://www.usu.edu/beetle
U52A-04 11:05h
Climatological, hydrological and vegetation change for the past 15,000 years based upon a new
network of high resolution lake sites in the Sierra Nevada and Unita Mountains
* MacDonald, G M (macdonal@geog.ucla.edu) , Department of Geography, UCLA, Los Angeles, CA
90095-1524 United States
Moser, K A (katrina.moser@csbs.utah.edu) , Department of Geography, University of Utah, Salt Lake
City, UT 84112-9155 United States
Porinchu, D F (porinchu.1@osu.edu) , Department of Geography, The Ohio State University, Columbus,
OH 43210-1361 United States
Bloom, A (amy.bloom@geog.utah.edu) , Department of Geography, University of Utah, Salt Lake City,
UT 84112-9155 United States
Potito, A (potito@ucla.edu) , Department of Geography, UCLA, Los Angeles, CA 90095-1524 United
9
States
Petel, A (apost@ucla.edu) , Department of Geography, UCLA, Los Angeles, CA 90095-1524 United
States
Instrumented lake and watershed climatic data along with lake sediment surface samples and cores are
being used to develop and apply paleolimnological transfer functions to reconstruct climate change and
ecosystem response in the eastern Sierra Nevada Mountains of California and the Unita Mountains of
Utah. The selection of the two ranges provides a circum Great Basin perspective on natural climate
variability in the western mountains. The California study sites are located in the eastern Sierra Nevada.
Surface sediment samples and water samples have been analyzed from 57 lakes extending across an
altitudinal gradient of 1360 m. Transfer functions that estimate water temperature, salinity and depth on
the basis of lake diatom flora or chironomid fauna have been developed and published. Long cores have
been obtained from 8 lakes that provide a transect from treeline down to the sagebrush dominated Great
Basin. The lake records extend back between 9000 and 15,000 Cal yr BP. Pronounced warming of ~ 4.5
degrees C and development of modern conifer forest started by ~13,800 Cal yr BP. At ~11,000 Cal yr BP
temperatures were as warm or warmer than today. High resolution analysis shows that the general glacial
to interglacial warming was interrupted by a climatic reversal at approximately 13,000 Cal yr BP during
which time summer temperatures at mid-elevation lakes cooled by 4 to 6 degrees C. There was a
pronounced three part hydrological shift during this temperature reversal. The temperature reversal
corresponds in timing with Younger Dryas Stadial typical of circum North Atlantic records. There was
only a muted response to this episode at higher elevations and in the terrestrial vegetation. The cooling is
synchronous with the Younger Dryas Stadial. Between ~8000 and 4000 Cal yr BP there was pronounced
drying and lake drawdown at lower elevations. The period from 4000 Cal yr BP to the present has been
typified by shifts between relatively moist conditions, like the present, and drier multi-decadal intervals.
Dry intervals observed in low elevation records correspond in time to the Stine events which have been
deduced from radiocarbon dated stumps in lakes and river valleys in the eastern Sierra Nevada. At
present, 35 lakes in the Uintas have been sampled for surface sediments and two long cores have been
obtained. One of the cores is laminated throughout and offers the potential for sub-decadal to annual
resolution of past climatic variability. The records obtained show that the ecosystems of the western
mountains have experienced pronounced millennial to centennial/decadal scale climatic and hydrologic
variability as a natural component in their development and persistence. It is possible that
centennial/decadal scale shifts similar to those evident over the past 4000 years would occur in the future.
U52A-05 11:20h
Mountain Systems, Persistent Drought and the Vulnerability of Ecosystem Services: A Case Study
from Glacier National Park, USA
* Graumlich, L J (lisa@montana.edu) , Big Sky Institute, Montana State University, Bozeman, MT 59717
United States
Pederson, G T (gpederson@montana.edu) , Big Sky Institute, Montana State University, Bozeman, MT
59717 United States
Fagre, D (dan_fagre@usgs.gov) , USGS Rocky Mountain Science Center, Glacier National Park, West
Glacier, MT 59936 United States
Gray, S T (sgray@montana.edu) , USGS Desert Lab, 1675 West Anklam Road, Tucson, AZ 85745
United States
The recent, persistent drought in the Western United States has invigorated interest in the findings of
paleoclimatologists indicating that precipitation anomalies of a decade or more in duration are a
substantial component of natural climatic variability over the past millennium. Further, we have
10
accumulating evidence that large-scale, persistent climate features, such as the North Atlantic Oscillation
and the Pacific Decadal Oscillation, can entrain ecosystem processes at regional scales. Demographic
processes in fish, forests, and ungulates stand out as particularly compelling examples. These oft-cited
examples are also interesting because they demonstrate that the sustainable provision of "ecosystem
services" (i.e., the benefits people obtain from ecosystems) is subject to decadal-scale climatic variability.
In this paper, we present a regional example of how precipitation varies at decade and longer time scales
at Glacier National Park, Montana, USA. We examine how the climate variability expressed in Glacier
National Park is coherent with larger regional patterns in Western North America and is associated with
indices of large-scale atmospheric circulation features. We then explore how such variability might affect
the ecosystem services offered by Glacier National Park. Our goal is to broaden the discussion of the
impacts of climatic variability on protected areas by defining linkages between drought, climate regimes
and the sustainable provision of ecosystem services. Decade and longer climate anomalies, and the
attendant regime shift behavior, poses challenges for the management of ecosystem services in three
ways. First, long-term climate reconstructions challenge the conventional strategy of defining mean, or
average, conditions as a management tool. Second, step-like changes from one climate regime to another
are often dramatic and may provide evidence of change that, in turn, may (or may not) represent humaninduced changes. Third, decade-length persistence of either deficits or abundances of climate-related
services solidify institutional arrangements that, in the long run, may not be robust under global climate
change scenarios. After exploring this question in the data-rich context of Glacier National Park, we will
suggest the broader implications of decade and longer scale variability for the services that we have come
to expect from our parks and wildlands.
U52A-06 11:35h
Advance of Trees and Krummholz Into Alpine Tundra
* Malanson, G P (george-malanson@uiowa.edu) , University of Iowa, Department of Geography, Iowa
City, IA 52242 United States
Zeng, Y (yu-zeng@uiowa.edu) , University of Iowa, Department of Geography, Iowa City, IA 52242
United States
Butler, D R (db25@txstate.edu) , Texas State University, Department of Geography, San Marcos, TX
78666 United States
Resler, L M (resler@vt.edu) , Virginia Tech, Department of Geography, Blacksburg, VA 24061 United
States
Invasion of alpine tundra by trees is an expected outcome of climatic change, but observed responses are
equivocal. To examine the invasibility of tundra we consider what might limit or facilitate seedling
establishment and subsequent development into krummholz or trees. At the seed stage barriers to success
include landing on an impenetrable surface. Many tundra sites are underlain by active or relict
solifluction, however, and data show that these sites present opportunities for the exposure of fine soil
through turf exfoliation on tread-riser boundaries. At the seedling stage negative and positive feedbacks
are both present. A simulation with negative feedback in dense trees and positive feedback with fewer
trees produces an advance of trees into tundra in which the rates vary in correlation with a fractal spatial
pattern, not climatic change. Because the spatiotemporal patterns of tree advance into tundra will be
related to climatic change nonlinearly and will, to some degree, be controlled by geomorphic conditions,
places may respond individualistically.
U52A-07 11:50h
11
Increasing Temperatures in Mountainous Regions of the Western United States and Effects on
Insect Outbreaks
* Hicke, J A (jhicke@nrel.colostate.edu) , Natural Resource Ecology Laboratory, Colorado State
University, 1499 Campus Delivery, Fort Collins, CO 80523 United States
Logan, J A (jalogan@fs.fed.us) , USDA Forest Service, Rocky Mountain Research Station, Logan, UT
84321 United States
Powell, J (powell@math.usu.edu) , Department of Mathematics and Statistics, Utah State University,
Logan, UT 84322 United States
Ojima, D S (dennis@nrel.colostate.edu) , Natural Resource Ecology Laboratory, Colorado State
University, 1499 Campus Delivery, Fort Collins, CO 80523 United States
Global temperatures have increased over the last 100 years and are projected to continue to rise as a result
of greater atmospheric carbon dioxide concentrations. However, temperatures at high elevations are not
uniformly increasing. Instead, trends vary regionally and depend on the time period of interest. Climate,
specifically temperature, plays a major role in regulating outbreaks of bark beetles by synchronizing
attacks on host trees during favorable temperature conditions. In this study, we characterize patterns of
temperature change over the last 100 years for mountainous regions in the western United States, utilizing
the VEMAP gridded database but also considering additional sources (e.g., SNOTEL, HCN). Although
temperatures at higher elevations have changed little over the long term, recent decades have experienced
warming. Projected temperatures in this region continue to warm through 2100. We explored the effects
of changing temperatures on the spatial patterns of mountain pine beetle outbreak using a phenology
model that predicts potential infestation. We show that temperature conditions suitable for outbreak
existed in the past 100 years for most locations occupied by a favored host, lodgepole pine. At lower
elevations, projected warming resulted in reductions in potential outbreak area. At higher elevations,
potential outbreak area increased as temperatures became more favorable, then decreased as conditions
became too warm to support synchrony of beetle attack. The shifts in climatically suitable conditions for
mountain pine beetle outbreak have significant implications for lodgepole pine, a species dependent on
disturbance, as well as other high-elevation pine ecosystems that are susceptible to infestation.
U52A-08 12:05h
Emergent Urban-Landscape Interactions in Mountain Catchments
* Werner, B (bwerner@ucsd.edu) , Complex Systems Laboratory, Institute of Geophysics and Planetary
Physics, University of California - San Diego, La Jolla, CA 92093-0225 United States
McNamara, D (dmcnamara@ucsd.edu) , Complex Systems Laboratory, Institute of Geophysics and
Planetary Physics, University of California - San Diego, La Jolla, CA 92093-0225 United States
Kelso, A (kelso@zinn.ucsd.edu) , Complex Systems Laboratory, Institute of Geophysics and Planetary
Physics, University of California - San Diego, La Jolla, CA 92093-0225 United States
Ipiktok, T (ipiktok@zinn.ucsd.edu) , Complex Systems Laboratory, Institute of Geophysics and Planetary
Physics, University of California - San Diego, La Jolla, CA 92093-0225 United States
The margins of mountain catchments can offer attractive residential attributes, but development is subject
to an array of significant hazards. The question of how urban expansion and natural processes interact as a
system to produce long-term, emergent patterns of coupled human-landscape dynamics is addressed in a
model that treats natural processes on intermediate time scales on a cellular grid and urban processes
using agent-based models of markets and local/regional government. In the model, shrubland vegetation
grows between fires, wildfires consume vegetation and residences and promote erosion, and landslides,
floods and sediment-laden debris flows damage or destroy residences. Developer agents build
12
developments whose size and location are based on projected profits; homeowning agents buy houses
based on projected appreciation and attributes such as view and commute distance. Based on their
predicted effect on tax revenues, government agents approve developments; mitigate fires with prescribed
burns; mitigate landslides, floods and debris flows with slope stabilization, debris basins, reservoirs and
channel stabilization and entrenchment; and suppress fires. Initial investigation of the model has focused
on long-time-scale behavior of the urban-wildland boundary. Mitigation measures filter out short, smallamplitude fluctuations in this boundary. As the relative time scales and interaction magnitudes
characterizing natural processes, development and government action are varied, a nominally stable
boundary becomes unstable to irregular, long period fluctuations that can be spatially complex. The role
that market externalities play in producing nonoptimal states will be discussed. Supported by the Andrew
W. Mellon Foundation.
Author(s) (2004), Title, Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract #####-##.
Union [U]
U53A MCC:level 2 Friday 1340h
Challenges to Mountain Water Resources and Ecosystems III Posters
Presiding:D Cayan, Scripps Institution of Oceanography; C Millar, PSW Research Station, USDA Forest
Service; D Fagre, U.S. Geological Survey Science Center
U53A-0701 1340h
Evaluation of the representativeness of automated snow water equivalent sensors in the Rio Grande
headwaters using intensive field observations, remotely sensed snow cover data, and distributed
snowmelt models
* Molotch, N P (molotch@cires.colorado.edu) , Cooperative Institute for Research in Environmental
Sciences, University of Colorado, Boulder, 216 UCB, Boulder, CO 80309-0216 United States
Bales, R C , Division of Engineering, University of California, Merced, P.O. Box 2039 , Merced, CA
95344 United States
In spring 2001 and 2002 monthly snow surveys (i.e. April, May, and June) were undertaken to assess the
spatial and temporal representativeness of snow water equivalent (SWE) values recorded at six snow
telemetry (SNOTEL) stations in the Rio Grande headwaters. Snow depth data were interpolated using
binary regression tree models and combined with snow density data and remotely sensed snow covered
area to estimate the spatial distribution of SWE surrounding the SNOTEL sites. A physically based
energy and mass balance snowmelt model was used to simulate the depletion of snow cover throughout
the snowmelt season. Relative to the entire watershed, SNOTEL site locations are not representative of
physiographic variables known to control snow distribution (i.e. elevation, slope, and incident solar
radiation). At the watershed scale (3419 km$^{2}$) SNOTEL sites are located toward the western
boundary of the watershed, an area of high snow cover persistence. Even relative to the 16, 4 and 1
km$^{2}$ areas that surround them, SNOTEL stations are not representative of the physiographic
variables known to control snow distribution. These physiographic biases vary from site-to-site, with five
of six sites located on relatively flat terrain and hence having a positive solar radiation bias. For the two
water years studied, certain sites showed consistent overestimates of SWE relative to the surrounding 16,
13
4, and 1-km$^{2}$ areas. Other sites showed variability in SWE bias during the two years, as regressiontree model results suggested that different physiographic variables controlled snow distribution during the
two water years. The results presented here will improve the ability to upscale SNOTEL data for
evaluating and calibrating remote sensing algorithms and initializing, evaluating, and updating modeling
efforts at the regional scale.
U53A-0702 1340h
Climate Mapping Challenges in Mountainous Regions
* Daly, C (daly@coas.oregonstate.edu) , Spatial Climate Analysis Service, Oregon State University, 326
Strand Agriculture Hall, Corvallis, OR 97331 United States
Gibson, W P (gibson@coas.oregonstate.edu) , Spatial Climate Analysis Service, Oregon State University,
326 Strand Agriculture Hall, Corvallis, OR 97331 United States
Taylor, G H (taylor@coas.oregonstate.edu) , Spatial Climate Analysis Service, Oregon State University,
326 Strand Agriculture Hall, Corvallis, OR 97331 United States
Doggett, M K (mdoggett@coas.oregonstate.edu) , Spatial Climate Analysis Service, Oregon State
University, 326 Strand Agriculture Hall, Corvallis, OR 97331 United States
Mountainous regions encompass some of the most complex climates in the world. The presence of major
topographic features, sometimes interacting with coastal effects, creates a myriad of spatially complex
precipitation and temperature regimes. Typically, only a small number of these regimes are wellrepresented by surface observations. Therefore, producing accurate climate maps for these regions can be
quite challenging. PRISM, a knowledge-based climate mapping system, was originally developed in 1991
to map precipitation in the mountainous western United States. Since then, it has been both generalized
and refined to model more climate variables and address more climatological processes, and its use has
expanded worldwide. Model improvements have come primarily as a result of lessons learned through
repeated applications of the model and peer-review of the results. This paper will survey some of the
major climatological processes driving temperature and precipitation patterns in mountainous regions, and
how PRISM accommodates these processes. These include elevational gradients, rain shadows, coastal
influences, temperature inversions, cold air drainage, and the varying orographic effectiveness of terrain
features. Specific case studies will be drawn from Oregon, California, Colorado, and other locations.
<a href='http://www.ocs.oregonstate.edu/prism/' >http://www.ocs.oregonstate.edu/prism/
U53A-0703 1340h
Impact of Retreating Glaciers in an Intermontane Andean Watershed: Hydrochemical Analysis
From the Callejon de Huaylas, Per\'{u}
* Mark, B G (mark.9@osu.edu) , Department of Geography, The Ohio State University, 154 N Oval
Mall, Columbus, OH 43210 United States
McKenzie, J M (jeff_mck@yahoo.com) , Department of Earth Sciences, Syracuse University, Syracuse,
NY 13244 United States
Welch, K A (welch.189@osu.edu) , Byrd Polar Research Center, 1090 Carmack Road The Ohio State
University, Columbus, OH 43210 United States
The Callejon de Huaylas, Per\'{u}, is a well-populated 5000 km$^{2}$ watershed of the upper Rio Santa
river draining the glacierized Cordillera Blanca. This tropical intermontane region features rich
agricultural diversity and valuable natural resources, but currently receding glaciers are causing concerns
14
for future water supply. A major question concerns the relative contribution of glacier meltwater to the
regional stream discharge-from first order basins to the whole watershed. In July, 2004, we collected 37
water samples from streams, springs and precipitation over a 2000 m vertical range within the watershed
and analyzed them for major dissolved ions and isotopic (\delta$^{18}$O) composition. The water
chemistry is used to establish the extent of variability in the surface waters, and to identify different
hydrologic end-member components. \delta$^{18}$O values for the waters range from -4.29\permil to 5.28\permil. There is a consistent trend towards lighter isotopes with greater percentage of glacier
coverage in tributary stream catchments of the Rio Santa, with some exceptions due to evaporative
enrichment in lakes. Samples taken along transects of these glacierized tributary streams become more
isotopically enriched with lower elevation and greater distance from the glaciers. However, waters from
the Rio Santa become less enriched with lower elevation. We hypothesize that the distribution of glacier
mass in the mountain range causes a greater volume of glacial meltwater to join the Rio Santa at lower
elevations. The water generally has a Ca-Mg-HCO$_{3}$ chemical signal. Samples along transects of
tributary valleys show an increase in TDS and the Na:Mg concentration ratio with decreasing elevation.
We see geochemical evidence for a small groundwater source in the tributaries and the Rio Santa. We
propose that distinct chemical signatures of source water end-members may provide a means of
quantifying the volumetric contribution of glacier meltwater over time.
U53A-0704 1340h
The relationship between snowpack and seasonal low flows in the Sierra Nevada: climate change
and water availability in California
* Godsey, S E (godseys@eps.berkeley.edu) , University of California-Berkeley, Dept. of Earth &
Planetary Science 307 McCone Hall # 4767, Berkeley, CA 94720-4767 United States
Kirchner, J W (kirchner@seismo.berkeley.edu) , University of California-Berkeley, Dept. of Earth &
Planetary Science 307 McCone Hall # 4767, Berkeley, CA 94720-4767 United States
Seasonal low flows are important for sustaining aquatic ecosystems, and for supplying human needs
during mid-summer. When the timing of water supply and demand do not coincide, humans rely on both
natural and artificial storage. In California, the gap in timing between supply and demand is bridged
primarily by the Sierra Nevada snowpack, which slowly melts throughout the spring and summer.
However, most future climate scenarios suggest a decreased snowpack in the Sierra. Previous studies
have investigated changes in snowmelt timing and spring snowmelt flood events. Here, by contrast, we
explore how changes in the Sierra Nevada snowpack will affect annual low flows. We have identified all
of the gauged catchments in the Sierra Nevada with unimpaired streamflow records and with at least ten
years of overlapping snowpack and streamflow data. In each of these catchments, we have analyzed up to
40 years of historical snow and streamflow records. We find that annual minimum, mean, and maximum
flows in these catchments all increase and decrease proportionally, or more-than-proportionally, as the
annual peak snowpack water content changes from year to year. For every 10% decrease in snowpack,
there is a 9-17% decrease in annual minimum flow. Minimum flows also occur earlier in years with
smaller snowpacks; for every 10% decrease in snowpack, minimum flows occur 3-7 days earlier in the
year. Finally, we find that in some catchments, annual low flows are significantly correlated not only with
that year's snowpack, but with the previous year's snowpack as well. That is, seasonal low flows in some
Sierra Nevada catchments exhibit a multi-year "memory" of snowmelt water inputs. We evaluate possible
mechanisms that might underlie this observed memory effect. If these observed relationships between
snow and flow hold in the future climate regime, the projected decrease in snowpack is likely to have a
severe effect on seasonal low flows.
U53A-0705 1340h
15
Uncertainty in Projections of Impacts of Climate Change on Sierra Nevada mountain hydrology in
California
* Maurer, E P (emaurer@engr.scu.edu) , Santa Clara University Civil Engineering Department, 500 El
Camino Real, Santa Clara, CA 95053-0563 United States
Duffy, P B (pduffy@llnl.gov) , Lawrence Livermore National Laboratory Climate and Carbon Cycle
Modeling Group, Atmospheric Sciences Division, Livermore, CA 94551-0808 United States
Understanding the uncertainty in the projected impacts of climate change on California's Sierra Nevada
hydrology will clarify where hydrologic impacts can be expected with higher confidence, and will help
address scientific questions related to possible improvements in climate modeling. In this study, we focus
on California, a region that is vulnerable to hydrologic impacts of climate change. We statistically bias
correct and downscale the monthly temperature and precipitation projections from 10 global climate
models (GCMs) from the Coupled Model Intercomparison Project. These GCM simulations include both
a control period (with unchanging CO2 and other atmospheric forcing) and a perturbed period with a 1percent per year increase in CO2 concentration. We force a distributed hydrologic model with biascorrected and statistically downscaled GCM data, and generate streamflow at strategic points in the
Sacramento-San Joaquin River basin. Among our findings are that inter-model variability does not
prevent significant detection of decreases in summer low flows, increases in winter flows or the shifting
of flow to earlier in the year. Uncertainty due to sampling of a 20-year period in an extended GCM
simulation accounts for the majority of inter-model variability for summer and fall months, while varying
GCM responses to temperature and precipitation forcing add to the variability in the winter. Inter-model
variation in projected precipitation accounts for most of the uncertainty in winter and spring flow
increases in both the North and South regions, with a greater influence in the North. The influence of
inter-model precipitation variability on May-September streamflow decreases in later years, as higher
temperatures dominate the hydrologic response, and melting snowpack has less influence.
U53A-0706 1340h
Stream Discharge and Sediment Load Variation During Three Dry Years at Kings River
Experimental Watershed in the Southern Sierra Nevada in California
* Eagan, S M (seagan@fs.fed.us) , USDA Forest Service Research, PSW, Sierra Nevada Research
Center, 2081 E Sierra Ave, Fresno, CA 93710 United States
Johnson, C (crjohnson@fs.fed.us) , USDA Forest Service Research, PSW, Sierra Nevada Research
Center, 2081 E Sierra Ave, Fresno, CA 93710 United States
Hunsaker, C T (chunsaker@fs.fed.us) , USDA Forest Service Research, PSW, Sierra Nevada Research
Center, 2081 E Sierra Ave, Fresno, CA 93710 United States
Dolanc, C (cdolanc@fs.fed.us) , USDA Forest Service Research, PSW, Sierra Nevada Research Center,
2081 E Sierra Ave, Fresno, CA 93710 United States
Lynch, M (melynch@fs.fed.us) , USDA Forest Service Research, PSW, Sierra Nevada Research Center,
2081 E Sierra Ave, Fresno, CA 93710 United States
The Kings River Experimental Watershed (KREW) is now in its third year of data collection on eight
small watersheds from 1600-2400 m in the Sierra Nevada. We are collecting meteorology, stream
discharge, sediment load, water chemistry, stream microclimate, shallow soil water chemistry, vegetation,
macro-invertebrate and air quality data. This paper examines connections between meteorology, stream
discharge and sediment yield in water years 2003 and 2004, which were generally dry with below average
snow packs. The current effort is to establish a baseline variation in these watershed characteristics prior
16
to treatments. The Sierra National Forest will thin and/or prescribed burn six of these watersheds in 2006
and 2007 while two will remain as controls.
<a href='http://www.fs.fed.us/psw/programs/snrc/' >http://www.fs.fed.us/psw/programs/snrc/
U53A-0707 1340h
High-Elevation Response of Conifers to Climate Change in the Sierra Nevada and Western Great
Basin, USA: Treeline Elevation is Not the Primary Effect
* Millar, C I (cmillar@fs.fed.us) , USDA Forest Service, PSW Research Station, P.O. Box 245, Berkeley,
CA 94701 United States
Westfall, R D (rwestfall@fs.fed.us) , USDA Forest Service, PSW Research Station, P.O. Box 245,
Berkeley, CA 94701 United States
King, J C (lonepine@bigsky.net) , Lone Pine Research, 2604 Westridge Dr., Bozeman, MT 59715 United
States
Delany, D L (ddelany@fs.fed.us) , USDA Forest Service, PSW Research Station, P.O. Box 245,
Berkeley, CA 94701 United States
Alden, H A (HAA@scmre.si.edu) , Smithsonian Center for Materials Research and Education, 4210
Silver Hill Rd., Suitland, MD 20746 United States
Traditionally change in alpine treeline elevation has been treated as the primary response by conifers to
climate change, and considerable effort has gone into discriminating among complex climatic factors that
determine a binary move (up or down slope). Four independent studies in the eastern Sierra Nevada (SN)
and western Great Basin (GB), which assessed conifer response to historic climates at scales of decades to
millennia, suggest that changes in slope, aspect, growth form, species composition, and forest structure
are equally if not more important than changes in treeline elevation. (1) Over the past 3.5 millennia,
limber pine (Pinus flexilis) alternately grew in sparse populations on highly restricted (NE-facing) sites in
the Wassuk Range (GB) and sites in the SN during centuries of drought versus widespread on many
slopes and aspects within similar elevation zones during favorable climate periods. (2) During the past
millennium, the summit of Whitewing Mtn (near current local treeline, SN) has been alternately occupied
by a mixed conifer forest (seven species), scattered, dwarfed pines (one species) and no trees, varying
with distinct climate periods. (3) Treeline elevation of whitebark pine (P. albicaulis) in the Yosemite
National Park region (SN) over the last millennium has remained stable, whereas climate periods are
marked by changes in growth, growth form and forest density. (4) During the 20th century, type
conversions from meadow to forest and from bare ground (former snowfields) to forest correspond to
multi-decadal climate variability. These studies suggest that future global change may unfold as complex
changes in slope, aspect, forest composition and structure rather than simple shifts in species and plant
communities up or down slope.
U53A-0708 1340h
Reconstructing a Past Climate Using Current Multi-species' Climate Spaces
* Westfall, R D (bwestfall@fs.fed.us) , Sierra Nevada Research Center USDA Forest Service PSW
Research Station, PO Box 245, Berkeley, CA 94701
Millar, C I (cmillar@fs.fed.us) , Sierra Nevada Research Center USDA Forest Service PSW Research
Station, PO Box 245, Berkeley, CA 94701
17
We present an analysis of a ghost forest on WhiteWing Mt at 3000 m in the eastern Sierra Nevada,
southeast of Yosemite NP. Killed by a volcanic eruption about 650 years ago, the deadwood on
WhiteWing dates by standard tree-ring analysis to 800-1330 CE, during the Medieval Warm Anomaly.
Individual stems have been identified by wood anatomical characteristics as Pinus albicualis, P.
monticola, P. jeffreyi, P. contorta, P. lambertiana, and Tsuga mertensiana. With the exception of P.
albicualis, which is currently in krummholz form at this elevation, the other species are 200 m or more
lower in elevation. One, P. lambertiana, is west of the Sierran crest and 600 m lower in elevation.
Assuming that climatic conditions on Whitewing during this period were mutually compatible with all
species, we reconstruct this climate by the intersection of the current climatic spaces of these species. We
did this by first generating individual species' ranges in the Sierran ecoregions through selecting
vegetation GIS polygons from the California Gap Analysis database (UCSB) that contain the individual
species. Climatic spaces for each species were generated by the GIS intersection of its polygons with 4
km gridded polygons from PRISM climatic estimates (OSU); this was done for annual, January, and July
maximum and minimum temperature, and precipitation, merged together for each species. Climatic
intersections of the species were generated from the misclassified polygons of a discriminant analysis of
species by the climatic data. The average data from these misclassified polygons suggest that the climate
on WhiteWing during the existence of this forest community was 230 mm, 1oC, and 3oC greater than
present in precipitation, and maximum and minimum temperature, respectively.
U53A-0709 1340h
High Elevation Monitoring in the North American Tropics: Ecosystem/Climate Relationships on
Nevado de Colima, Mexico
* Hartsough, P (phartsou@unr.nevada.edu) , Graduate Program of Hydrologic Sciences, University of
Nevada, Reno MS 154, Reno, NV 89557 United States
Biondi, F (fbiondi@unr.edu) , Graduate Program of Hydrologic Sciences, University of Nevada, Reno
MS 154, Reno, NV 89557 United States
Biondi, F (fbiondi@unr.edu) , Department of Geography, University of Nevada, Reno, Reno, NV 89557
United States
High elevation monitoring in the tropics is uncommon. Presented here are the 2001-2004 results of an
intensive field study from Nevado de Colima, Mexico. The site is at 3800 m at 19° 34' N, a few hundred
meters below tree line. We have been co-monitoring weather and tree growth at half-hour intervals, as
well as seasonally averaged stable isotopes throughout the hydrologic/biologic cycle. The site is under the
influence of the North American monsoon, which determines a wet-summer, dry-winter climatic regime.
Using point and band dendrometers, we have shown the response of high elevation Pinus hartwegii trees
to changing weather patterns and attempted to pinpoint factors related to onset and cessation of growth in
these high elevation tropical trees. Precipitation, temperature and relative humidity are shown to influence
stem size at a range of timescales. Along with the stable isotope data collected to date, we hope to build a
model of tree growth and stable isotope incorporation into tree-ring cellulose. This will allow a calibrated
chemical reconstruction of seasonal growth response to fluctuations in the monsoon over the length of the
tree ring record ($>$350yr). We also had the unfortunate experience of monitoring several of our
instrumented trees during a round-headed pine beetle (Dendroctonus adjunctus) infestation following an
exceptionally dry winter the year before. These data may provide additional insight into tree response to
drought stress and physiological response to bark beetle attacks.
<a href='http://woods.geography.unr.edu' >http://woods.geography.unr.edu
U53A-0710 1340h
18
GLORIA Alpine Plant Monitoring in the White Mountains, Inyo County, California.
* Jayko, A (ajayko@usgs.gov) , US Geological Survey, 3000 E. Line St., Bishop, CA 93514 United
States
Powell, F L (fpowell@ucsd.edu) , White Mountain Research Sta., 3000 E. Line St., Bishop, CA 93514
United States
Smiley, J T (jsmiley@wmrs.edu) , White Mountain Research Sta., 3000 E. Line St., Bishop, CA 93514
United States
Pritchett, D (skypilots@wmrs.edu) , White Mountain Research Sta., 3000 E. Line St., Bishop, CA 93514
United States
Dennis, A (adennis@calflora.org) , CalFlora, 937 San Pablo Ave, Albany, CA 94706 United States
Millar, C I (cmillar@fs.fed.us) , USDA Forest Service, PSW Research Station Box 245, Berkeley, CA
94701
Murrell, K E (kemurrell@ucdavis.edu) , Univ. of California, Davis, UCD, Davis, CA 95616 United States
The GLORIA project (Global Observation Research Initiative in Alpine Environments: www.gloria.ac.at)
is a worldwide effort coordinated by the University of Vienna Institute of Ecology and Conservation
Biology, to monitor climate effects on alpine peaks around the world. In the summer of 2004 the
University of California, White Mountain Research Station teamed up with the U.S. Forest Service to
initiate GLORIA monitoring sites on 4 summits in the White Mountains. The lower three summits consist
of granitic rock, and range from 3240m to 3975m in elevation, while the upper summit is on metavolcanic
rock on the shoulder of White Mountain Peak at 4285m. For each summit we followed the rigorous
GLORIA sampling design and recorded baseline data on plant species composition, cover, and frequency.
Permanent monitoring plots were set up, and dataloggers installed to measure soil temperature. In
addition, we are discussing ways to augment the standard GLORIA sampling protocol by setting up a
White Mountain "GLORIA master site." This would involve (1) remeasurement of the GLORIA summits
using alternative sampling procedures, for example random quadrat sampling, to facilitate crosscomparison with other monitoring efforts by agency and university scientists, (2) a parallel summit
transect on a chemically contrasting bedrock lithology, formally known as the Reed Dolomite, which
produces magnesium-rich carbonate soils, and is the principle host rock to the ancient Bristlecone forest,
.and (3) expanding sampling to include animal taxa. We also plan to complete a detailed geomorphic and
geologic description of each site to include in the monitoring database.
<a href='http://www.wmrs.edu/projects/gloria project/default.htm' >http://www.wmrs.edu/projects/gloria
project/default.htm
U53A-0711 1340h
A New GLORIA Target Region in the Sierra Nevada, California, USA; Alpine Plant Monitoring
For Global Climate Change
Dennis, A (adennis@calflora.org) , CalFlora, 937 San Pablo Ave., Albany, CA 94706 United States
* Millar, C I (cmillar@fs.fed.us) , USDA Forest Service, PSW Research Station, P.O. Box 245, Berkeley,
CA 94701 United States
Murrell, K E (kemurrell@ucdavis.edu) , University of California, Dept of Environmental Horticulture,
Davis, CA 95616 United States
The Global Observation Research Initiative in Alpine Environments (GLORIA) is an international
research project with the goal to assess climate change impacts on vegetation in alpine environments
worldwide. Standardized protocols direct selection of each node in the network, called a target region,
19
which consists of a set of four geographically proximal mountain summits at elevations extending from
treeline to the nival zone. For each summit, GLORIA specifies a rigorous mapping and sampling design
for data collection, with re-measurement intervals of five years. Whereas target regions have been
installed in six continents, prior to 2004 none was completed in North America. In cooperation with the
Consortium for Integrated Climate Research in Western Mountains (CIRMOUNT), three target regions
were completed by September 2004, one in the Sierra Nevada, California, one in the White Mountains,
California, and one in Glacier National Park, Montana. The SIERRA NEVADA (GLORIA code: SND)
target region lies along the Sierra Nevada crest in the Yosemite National Park/Mono Lake region. The
four summits well represent the GLORIA design standards, being little visited by climbers, outside
domestic grazing allotments, relatively rounded in shape, situated within one climate region, related
substrate types (metamorphic), and extending from treeline to the highest elevation zones in the area. The
four summits include the subordinate peak of Mt Dunderberg (3744m), two lesser peaks of Mt
Dunderberg (3570m and 3322m) and a summit along the Yosemite National Park boundary region south
of Mt Conness (3425m). Preliminary data indicate that numbers of vascular plant species, from lowest to
highest summit, were 40, 36, 12, 22 (total for SN, 67). Only 1 species (Elymus elymoides ssp.
californicus) occurred on all four summits; 8 species occurred on three summits; no exotic species was
detected. The most distant summit, also most distinct in substrate, had the largest number of unique
species. The genus Carex (Cyperaceae) had the most species represented (five). Only one tree species
(Pinus albicaulis) occurred within the summit areas. Data analysis of the baseline measurements has just
begun; the standardized GLORIA protocols will enable direct comparisons among summits within the
target region, across target regions in California, among the three target regions in North America, and
with established GLORIA regions in other continents.
U53A-0712 1340h
The Glacier National Park GLORIA Project: A new US Target Region for Alpine Plant Monitoring
Installed in the Northern Rocky Mountains, Montana
Holzer, K (karen_holzer@usgs.gov) , USGS Northern Rocky Mountain Science Center, USGS Science
Center, Glacier National Park, West Glacier, MT 59936 United States
* Fagre, D (dan_fagre@usgs.gov) , USGS Northern Rocky Mountain Science Center, USGS Science
Center, Glacier National Park, West Glacier, MT 59936 United States
The Global Observation Research Initiative in Alpine Environments (GLORIA) is an international
research network whose purpose is to assess climate change impacts on vegetation in alpine environments
worldwide. A standard protocol was developed by the international office in Vienna, Austria, and has
specific site requirements and techniques that allow sites to be compared worldwide. This protocol
requires four summits to be selected within a target region, covering zonal differences of subalpine to
nival, and on each of these summits intensive vegetation plots are set up and monitored on a five year
interval. Only three target regions in North America have been completed to date, one in Glacier National
Park, Montana, and the other two in the Sierra Nevada and White Mountains, California. The four
GLORIA summit plots in Glacier National Park were completed over the summers of 2003 and 2004.
Because the Continental Divide bisects Glacier National Park (north to south), we chose summits only
East of the divide to stay within a similar climatic pattern. Establishing sites was difficult due to the steep
and rocky glaciated terrain and the remoteness of suitable sites that required multi-day approaches. Our
highest summit (Seward Mtn. 2717 m) is the northernmost and our lowest summit (Dancing Lady Mtn.
2245 m) is southernmost. Treeline is strongly influenced by terrain and is significantly more variable than
in the central Rocky Mountains. This also was true of zonal differences of alpine vegetation. Subalpine
and even grassland species were found on the same summits as upper alpine species and areas considered
subnival. While different zonal areas often occurred on one summit, they were highly influenced by the
20
aspect and slope of that summit area. Between 51 and 82 vascular plants were documented on each
summit. There was a high degree of variability in species diversity and percent cover on each summit that
was correlated to directional exposure. The summit morphology caused loose vegetative associations, or
micro-communities, that varied with exposure, slope angle, and substrate character. Species that exhibited
dominance within the target region were Smelowskia calycina var. americana, Polemonium viscosum,
Achillea millefolium, Erigeron compositus var. glabratus, and Potentilla fruticosa L. These species
reflected the same variability in percent cover on the four sides of the summit areas as did the vegetation
as a whole, but were present on all sides.
U53A-0713 1340h
Competing Interests and Concerns in the Rio Grande Basin: Mountain Hydrology, Desert Ecology,
Climate Change, and Population Growth
* Rango, A (alrango@nmsu.edu) , USDA/ARS/Jornada Experimental Range, New Mexico State
University, 2995 Knox St., Las Cruces, NM 88003 United States
In the mountainous American Southwest, the Rio Grande basin is a prime example of how conflicts,
misconceptions, and competition regarding water can arise in arid and semi-arid catchments. Much of the
Rio Grande runoff originates from snow fields in the San Juan Mountains of southern Colorado and the
Sangre De Cristo Mountains of northern New Mexico, far from population centers. Large and rapidly
growing cities, like Albuquerque, Las Cruces, El Paso, and Juarez, are located along the Rio Grande
where it flows through the Chihuahuan Desert, the largest desert in North America(two NSF Long Term
Ecological Research sites are located in the desert portion of the basin). As a result, the importance of
snowmelt, which makes up 50-75% or more of the total streamflow in sub-basins above Elephant Butte
Reservoir(in south central New Mexico) is hardly known to the general public. Streamflow below
Elephant Butte Reservoir is rainfall driven and very limited, with the lower basin receiving only 170-380
mm of precipitation annually, most of it occurring during the months of July-September. Extreme events,
such as drought and flooding, are not unusual in arid basins, and they are of increasing concern with
regard to changes in frequency of such events under the impending conditions of climate change. Current
water demands in the basin already exceed the water supply by 15% or more, so streamflow
forecasts(especially from snowmelt runoff) are extremely valuable for efficient water management as well
as for proper apportionment of water between Colorado, New Mexico, and Texas under the Rio Grande
Compact of 1938 and between the U.S. and Mexico under the Treaty of 1906. Other demands on the
water supply include Indian water rights, flood regulation, irrigated agriculture, municipal and industrial
demands, water quality, riverine and riparian habitat protection, endangered and threatened species
protection, recreation, and hydropower. To assess snow accumulation and cover and to produce
streamflow forecasts, several techniques are being employed including manual snow surveys, automated
SNOTEL measurements, satellite snow cover extent measurements, development of snow cover depletion
curves, and input of these data to the Snowmelt Runoff Model(SRM) and other models for forecasting.
Early season(November-January) SNOTEL measurements of snow water equivalent can be used in
regression approaches to estimate streamflow volumes early enough to provide growing season planning
for the types of crops to plant. Satellite snow cover is used directly in SRM for daily flow forecasts
throughout the melt season starting as early as March. Additionally, SRM can automatically produce
future hydrographs for climate change scenarios. For large river basins in arid and semi-arid areas, new
technologies, like remote sensing, will be valuable in assisting water managers to make more efficient use
of their limited water supply. Additionally, like meteorologists have done for the last 40 years,
hydrologists need to make use of remote sensing data to communicate in real time with the public on the
effects of snow accumulation, melt, and snowmelt runoff on human activities.
21
U53A-0714 1340h
Mountain Snowpack, Lowland Winter Precipitation, and Variability in Three Western US
Mountain Ranges
* Losleben, M V (markl@culter.colorado.edu) , INSTAAR, University of Colorado, 818 County Road
116, Nederland, CO 80466 United States
Pepin, N (nicholas.pepin@port.ac.uk) , University of Portsmouth, Buckingham Bldg, Lion Terrace,
Portsmouth, Hants, POI3HE United Kingdom
Demands on mountain snowpack in the Western United States are increasing explosively and the margin
between water supply and demand is disappearing. Since snowpack is the primary water source in most
regions, this paper examines high elevation snowpack in localized regions of three mountain ranges of the
western United States and contrasts this to cumulative winter precipitation in their abutting lowlands. The
three regions are the Rockies, Cascades, and the Sierra Nevada. Through examination of inter-annual
variability, extremes, and trends we found that snowpack variability is greatest in the Cascades and least
in the Rockies. Analysis of extreme snowpack shows strong relationships with circulation in the Cascades
and Sierra, but not in the Rockies. Extreme occurrences of widespread low snowpack (i.e. in all three
ranges) are common, whereas those of widespread high snowpack are rare. Further, the relationship
between high elevation snowpack and adjacent lowland precipitation (LWP) is de-coupled, suggesting
that LWP should not be used as a proxy for upland snowpack conditions. At a finer spatial scale, two sites
six km apart on the east slope of the Colorado Front Range show similarly significant contrasts in
snowpack. Differences at this fine scale can also be resolved into different atmospheric circulation
patterns. In conclusion, our analyses suggest that the snowpack in the Cascades may be the most sensitive
to future climate change, while that in the Rockies the least.
U53A-0715 1340h
How the 2004 Onset of Snowmelt and Streamflow Varied with Elevation
* Lundquist, J D (jlundquist@ucsd.edu) , Scripps Institution of Oceanography, 9500 Gilman Dr., La
Jolla, CA 92093-0213 United States
Cayan, D R (dcayan@ucsd.edu) , Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA
92093-0213 United States
Cayan, D R (dcayan@ucsd.edu) , United States Geological Survey, Scripps Institution of Oceanography
9500 Gilman Dr., La Jolla, CA 92093-0224 United States
Dettinger, M D (mdettinger@ucsd.edu) , United States Geological Survey, Scripps Institution of
Oceanography 9500 Gilman Dr., La Jolla, CA 92093-0224 United States
In 2004, spring snowmelt began anomalously early across the Western United States. USGS-gaged
streams draining the Sierra Nevada, Cascades, and Rocky Mountains all recorded a spring pulse of
meltwater during the second week of March. However, data from streamgages monitoring nested
streamgages along the Tuolumne and Merced Rivers in Yosemite National Park suggest that this early
onset of melt did not occur uniformly at all basin scales and elevations. The Yosemite monitoring
network has been operational since summer 2001, and gages are located at elevations from 1200 m to
3300 m in basins with various slopes and aspects. In 2002, spring melt began uniformly at all monitored
elevations, and in 2003 spring melt began uniformly at all but the highest gage. However, in 2004, the
onset of spring snowmelt varied widely. For example, streamflow on the South Fork of the Tuolumne
River at 2040 m started flowing 7 March, and flows did not decline until the snowpack was depleted. In
contrast, a gage monitoring inflow to Fletcher Lake at 3109 m recorded no flow prior to 30 April. Many
22
gages at elevations between these extremes recorded a small flux of water in mid-March but no strong
increase in streamflow until mid- to late-April. These differences in snowmelt onset dates were supported
by not only in streamflow records but also by observation of vegetation, as botanists noticed flowers
blooming anomalously early below 2800 m but at their average times in higher regions. This paper seeks
to answer the following questions: What were the primary factors controlling the observed differences in
snowmelt onset dates in 2004? How did solar radiation and temperature inputs differ between 2002,
which had a uniform melt onset, and 2004? Was melt dominated by different processes at different
locations? What are the implications for climate forecasts, which predict earlier spring onsets in a warmer
climate? How can snowmelt and streamflow models better capture the different behavior observed at the
highest altitudes?
<a href='http://tenaya.ucsd.edu/{\sim}jessica/' >http://tenaya.ucsd.edu/{\sim}jessica/
U53A-0716 1340h
The hydrologic and biogeochemical response of undisturbed mountain ecosystems in the Western
United States to multiple stressors: Interactions between climate variability and atmospheric
deposition of contaminants
* Campbell, D H (Donald.Campbell@usgs.gov) , USGS, Mailstop 415, Federal Center, Lakewood, CO
80225 United States
Mast, M A (mamast@usgs.gov) , USGS, Mailstop 415, Federal Center, Lakewood, CO 80225 United
States
Clow, D W (dwclow@usgs.gov) , USGS, Mailstop 415, Federal Center, Lakewood, CO 80225 United
States
Ingersoll, G P (gpingers@usgs.gov) , USGS, Mailstop 415, Federal Center, Lakewood, CO 80225 United
States
Nanus, L (lnanus@usgs.gov) , USGS, Mailstop 415, Federal Center, Lakewood, CO 80225 United States
Wilderness areas and national parks of the West are largely protected from acute changes in land use such
as urbanization and natural resource development. However, the ecosystems in these areas are sensitive to
both climate variability and atmospheric deposition of acids, nitrogen (N), and toxic contaminants, and
these stressors interact in ways that we are just beginning to understand. Here we examine some examples
of the interactions between climate variability and nitrogen and mercury cycling in high elevation
watersheds. During the recent drought, which began in 2000, streamwater nitrate concentrations nearly
doubled in the Loch Vale watershed in Rocky Mountain National Park, exceeding 60 $\mu$M during
early snowmelt. Much of the elevated nitrate resulted from an increased percentage contribution to
streamwater of nitrate-rich shallow groundwater. In a nearby pond used for breeding by a threatened
amphibian species, nitrate concentrations were negligible but ammonium concentrations were extremely
high (850 $\mu$M) during the drought. In this case, organic N in pond sediments was likely mineralized
and released during cycles of drying and rewetting of pond sediments. Even after 2 years of near-average
precipitation, water levels remained below normal and ammonium concentrations remained elevated,
indicating that the hydrologic response of this small system has a timescale of many years. Mercury (Hg)
deposition at high elevations of the Rocky Mountains is comparable to that of the Midwest and Northeast,
but the processes that control Hg cycling in alpine/subalpine ecosystems are not well understood.
Methylation and bioaccumulation of Hg must occur before Hg reaches levels harmful to the ecosystem or
human health, and both climate and nutrient cycling affect these processes. Fluctuating water levels
caused by climate variability can mobilize Hg from lake and pond sediments, increasing reactivity and
bioavailability of Hg in the ecosystem. Increased nutrient release from the terrestrial ecosystem (eg. from
N saturation) may increase productivity and accumulation of organic matter, altering Hg cycling in the
23
aquatic system. Long durations of ice cover and thick snowpacks are likely to cause elevated methyl Hg
in aquatic ecosystems. Snow and ice cover on lakes promotes hypoxia in lake water, favoring production
and accumulation of methyl Hg- the percentage of methyl-Hg in lake water under snow and ice was as
much as 6 times greater than the percentage measured during late summer in a northwestern Colorado
lake. Analysis of long-term trends indicates that climate variability is increasing in the Mountain West.
Climatic extremes appear to exacerbate adverse impacts of atmospheric deposition, as well as stressing
ecosystems directly. A better understanding of these interactions is needed in order to predict the response
of mountain ecosystems to future changes in climate and atmospheric deposition.
U53A-0717 1340h
The Airborne Carbon in the Mountains Experiment
* Schimel, D (schimel@ucar.edu) , NCAR, 1850 Table Mesa Drive, Boulder, CO 80305 United States
Stephens, B (stephens@ucar.edu) , NCAR, 1850 Table Mesa Drive, Boulder, CO 80305 United States
Running, S (swr@umt.edu) , University of Montana, Department of Forestry, Missoula, MT 59812
United States
Monson, R (monsonr@colorado.edu) , University of Colorado, CIRES, Boulder, CO 80309 United States
Vukicevic, T (tomi@cire.colostate.edu) , University of Colorado, CIRES, Boulder, CO 80309 United
States
Ojima, D (dennis@nrel.colostate.edu) , Colorado State University, NREL, Ft Collins, CO 80523 United
States
Mountain landscapes of the Western US contain a significant portion of the North American carbon sink.
This results from the land use history of the region, which has a preponderance of potentially aggrading
mid-aged stands. The issue is significant not only because of the significant sink but because of the
vulnerability of that sink to drought, insects, wildfire and other ecological changes occurring rapidly in
the West. Quantification of the carbon budgets of western forests have received relatively limited
attention, in part because direct carbon flux measurements are believed to be difficult to apply in complex
landscapes. New techniques that take advantage of organized nighttime drainage flows may allow
quantification of respiration on scales inaccessible in level landscapes, while Lagrangian airborne
measurements may allow daytime fluxes to be quantified. Airborne and ground-based measurements
during the summer of 2004 in Colorado show substantial drawdown of atmospheric carbon dioxide
during the day and strong enrichment of the nocturnal boundary layer from nighttime respiration. We
present a strategy whereby in situ measurements at multiple scales, remote sensing and data assimilation
may be used to quantify carbon dynamics in mountain landscapes. Larger scales of integration may be
possible in mountainous than level landscapes because of the integrative flow of air and water, while
because of high heterogeneity, scaling from detailed local process studies remains difficult.
<a href='http://swiki.ucar.edu/acme' >http://swiki.ucar.edu/acme
U53A-0718 1340h
Trends in Snowfall Versus Rainfall for the Western United States
* Knowles, N (nknowles@usgs.gov) , USGS, 345 Middlefield Rd., MS496, Menlo Park, CA 94025
United States
Dettinger, M D (mdettinger@ucsd.edu) , Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla,
CA 92093-0224 United States
24
Cayan, D R , Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0224 United
States
The western U.S. depends heavily on snowpack to help retain its wintertime freshwater endowment into
the drier spring and summer months. A well-documented shift towards earlier runoff can be attributed to
1) more precipitation falling as rain instead of snow, and 2) earlier snowmelt. The present study shows a
regional trend toward a decreasing ratio of winter snow water equivalent (SWE) to total precipitation
since 1948. This trend is attributable to a shift toward more rainfall rather than a decrease in overall
precipitation. At the monthly scale, the trend is most pronounced in January (coastally) and March (westwide), corresponding to warming trends in those months for average wet-day maximum temperatures.
Implications for historical and projected runoff timing shifts are discussed.
U53A-0719 1340h
Meteorological Drought in the Mountainous West
* Gershunov, A (sasha@ucsd.edu) , Climate Research Division, Scripps Institution of Oceanography, La
Jolla, CA 92093-0224 United States
Cayan, D (dcayan@ucsd.edu) , Climate Research Division, Scripps Institution of Oceanography, La Jolla,
CA 92093-0224 United States
Cayan, D (dcayan@ucsd.edu) , US Geologic Survey, 9500 Gilman Drive, La Jolla, CA 92093 United
States
We examine meteorological drought in western North America in the climatic context of the entire
continent and adjacent ocean basins. Indices that describe the intensity and spatial extent of dry and wet
conditions are computed from station precipitation data at thousands of stations with daily precipitation
and temperature observations across North America as well as for geographically specific subsets
focusing on the Mountainous West. The evolution of regional drought histories will then be examined in
the context of local temperatures over land as well as climatic variability of the Pacific and Atlantic
basins as described by dominant sea surface temperature and atmospheric pressure patterns. The strong
interdecadal modulation of interannual extremes will be discussed. The relationships between dry, hot,
wet and cold conditions will also be described on a regional and seasonal basis. Additionally, we will
examine the contribution of daily precipitation extremes to wet and dry year totals as a function of
location and season. This will be done for specific extreme wet and dry episodes. By documenting and
understanding regional drought relationships with local weather and large-scale climate, we seek to gain
insight into the mechanisms that cause drought in the West. We aim especially to understand the causes of
the current persistent dry condition and in so doing project the likely future evolution of western North
American hydrology.
U53A-0720 1340h
Runoff Simulation over the Sierra Nevada Region Using a Coupled Regional Climate Model
* Jin, J (JimingJin@lbl.gov) , Berkeley National Lab., One Cyclotron Road, MS-90-1116, Berkeley, CA
94720
Miller, N L (NLMiller@lbl.gov) , Berkeley National Lab., One Cyclotron Road, MS-90-1116, Berkeley,
CA 94720
The land surface scheme (NOAH) in the current version of the Penn State-National Center for
Atmospheric Research (NCAR) fifth generation Mesoscale Model (MM5) insufficiently treats snowmelt
25
runoff over the Sierra Nevada region due to an insufficient treatment of the snow processes. To improve
snowmelt runoff simulation, we have coupled the newly released NCAR Community Land Model version
3 (CLM3) to MM5. CLM3 physically describes the mass and heat transfer within the snowpack using 5
snow layers that include liquid water and solid ice. Interactions among the snow, soil, and vegetation are a
function of the CLM3 mass and energy equations. Additionally, a river routing scheme has been adopted
in CLM3 to better describe the runoff hydrograph. Several observed datasets from different sources were
used to evaluate the model output, including snow depth, temperature, and precipitation from the
automated Snowpack Telemetry system, snow cover and vegetation indices from the MODIS satellite
data, and streamflow data from the U.S. Geological Survey. In this presentation, we describe the results
from an MM5-CLM3 integration from April 1 to June 30, 1998 with 60 km and 20 km nested domains.
The results indicate that the coupled model significantly improves the simulation of the snow mass,
resulting in a better description of the runoff in the Sierra Nevada region. The application of the river
routing scheme further improves the runoff hydrograph simulation. Meanwhile, MM5-CLM3 produces
better simulations for the surface air temperature and precipitation as it has more realistic descriptions of
the surface energy balance and hydrological cycle when compared to the original version of MM5 with
the NOAH land surface model. The coupling of the advanced CLM3 with MM5 significantly improves
the regional hydroclimate and water resources predictability.
Author(s) (2004), Title, Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract #####-##.