U51A-01 INVITED 08:00h
Integrating Climate and Ecosystem-Response Sciences in Temperate Western North American Mountains: The CIRMOUNT Initiative
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 high-elevations 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 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
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?
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
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 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
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
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 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
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 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
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.