Glaciers and Glacier Change in the , HASSAN J. BASAGIC; ANDREW G. FOUNTAIN Department of Geography, Portland State University, Portland, Oregon, 97207

Introduction Glacier Change Model results To account for different glacier geometries, the net balance of each lobe (below left) was Seven glaciers were selected to quantify the change in glacier extent. Selection of The Sierra Nevada extends over 640 km in eastern California and provides a vital multiplied by the glacier area altitude distribution (below right) to provide a mass balance glaciers was based on the availability of past data and location. These glaciers include source of California’s water supply from alpine snow. The range also contains Conness, East Lyell, West Lyell, Darwin, Goddard, Lilliput, and Picket glaciers (lower of -0.51 for the west lobe and -0.60 for the east lobe, indicating that both glaciers are out numerous small high-elevation (~3500 m) alpine glaciers, which act to delay spring left map). We reconstructed the glacier extents based on historic ground-based and of balance. The glaciers would continue shrinking under current climate conditions. runoff and are sensitive indicators of climate change. While knowledge of glacier aerial photographs and field measurements. Aerial photographs were scanned and shrinkage is common from repeat photography, there is little quantitative information 3900 imported into a GIS. Only late summer photographs, largely snow free, were used in on the subject. We present results here addressing three important questions: 1) How 3900 interpretation of the ice boundary. Aerial photographs were georeferenced to USGS many glaciers exist in the Sierra Nevada and where do glaciers occur; 2) How have 1944 aerial photograph 3800 orthorectified imagery. The historic glacier extents were interpreted from aerial photographs by tracing the ice 3800 they changed over the past 100 years; and 3) Why have these glaciers changed? 3700 boundary. Early 1900 extents are based on ground-based images and evidence from moraines. To obtain recent 3700 glacier areas, the extent of each glacier was recorded using GPS in 2004. The GPS data was post processed (2- Elevation (m) Elevation

Elevation (m) Elevation West lobe 3m accuracy), and imported into the GIS database. Glacier area were calculated with in the GIS database. 3600 West Lobe 3600 East Lobe East Lobe Lyell Glacier 3500 3500 00.050.1 Fractional Area Change Magnitude and Rate of change -2.0 -1.0 0.0 1.0 2.0 Net balance (WEQ m) Area (km2) 100% Fractional area change (left) is plotted based on each glacier’s 1900 area. August 7, 1903 The results indicate a large variation in overall magnitude of change. The G.K. Gilbert greatest loss in area occurred on the East Lobe of Lyell Glacier with a Future scenarios 75% loss of 0.17 km2 (-78%). The least change occurred in Lilliput Glacier with 3900 We ran scenarios for possible climate conditions West Lobe a loss of 0.02 (-30%). Conness, Darwin, Goddard, and Picket glaciers all in 2050: one with increased temperature (T) and lost approximately half of their surface area. Local variation in change is 3800 50% precipitation (P), and another with only increased Conness most evident between the East and West Lobes of Lyell which have lost Lyell West T. The net balance results on both lobes reveal a 3700 Climate norm Change in area in Change East Lyell 78% and 39% respectively. These results suggest that local topography Elevation (m) Elevation Scenario 1 Darwin large increase of melt (>100%) at lower elevations 25% strongly effects glacier response to changing climate conditions. Steep Scenario 2 September 5, 2004 Goddard only slight increase (+ 5%) in the accumulation Picket headwall cliffs may enhance winter accumulation through avalanching 3600 H. Basagic area of scenario 1 (upper right). Lilliput and reduce summer ablation by shading solar radiation. -3 -2 -1 0 1 2 0% Net balance (WEQ m) 1900 1920 1940 1960 1980 2000 Repeat Photography 2 Climate norm scenario 1 scenario 2 Scenario 1 We gathered historical photos from the United States Geological Survey (USGS) Earth 1 T = + 1.5 °C (Leung et al., 2004) Science Photographic Archive (http://libraryphoto.er.usgs.gov/) and re-photographed the scenes in P = + 21% (50 yr trend April 1st SWE at Tioga Pass) 0 the field from the same vantage point (Harrison 1960, Klett et al 1984). During the Surface energy balance model Scenario 2 -170% summers of 2003 and 2004, over 50 repeat images were collected from ten glaciers -183% To better understand the role of local topographic controls on these glaciers, we apply a simple surface energy -1 -196% -202% T = + 1.5 °C (Leung et al., 2004) Balance (m WEQ) located throughout the Sierra Nevada. The data serve as a visual comparison of change balance model to the East and West Lobes of Lyell Glacier. The spreadsheet model solves for melt on a monthly P = no change through time. A loss in both glacier area and volume can be observed in the results from -2 basis at seven individual locations (lower left) along the glacier’s surface based on PRISM climate data (lower West Lobe East Lobe Lyell Glacier, shown above. right) and Paterson’s (1994) surface energy balance equation: 3900

Q = SW ↓ (1 −α) + LW ↓−LW ↑ + Q + Q The results suggest that the East Lobe is more 3800 m H L 250 16 Lyell Glacier Sierra Nevada Glacier 14 sensitive to temperature changes as compared to 3700 The equation is made up of radiation and turbulent fluxes terms. 3512m elevation 12 the west lobe, likely because of differences in 200 West lobe Inventory (m) Elevation 3600 SW = shortwave (global) calculated using Solar Analyst (Fu and Rich, 1999) 10 elevation (above). Glacier area altitude distributions East Lobe 8 We performed an inventory of all reconstructed for 2050 using scenario 1 (right). The 3500 150 Sierra Nevada glaciers, perennial α = albedo values for fresh snow 0.84, Melting snow 0.74, ice 0.40 6 East Lobe has practically disappeared, while only 4 0 0.05 0.1 ice, and snowfields to understand 4 4 2 5 LW ↓↑ = Longwave = ε σT - ε σT 2 the upper region of the West Lobe remains. Area (km ) (! a a s s 100 the distribution and quantity of these Conness where ε and ε are emissivity of the air and the surface respectively. ε a s , a 0 Temperature (C) Precipitation (mm) Precipitation features. The GIS database is accounts both cloudy and clear sky conditions. σ is the Stefan-Boltzmann -2 constant, and T and T are air and surface temperatures. 50 based on USGS 7.5 minute a s -4 68 -6 (!(!7 Conclusion topographic quadrangle maps East and West Lyell QH = sensible heat = ρcpAu(Ta -Ti) 0 -8 All seven glaciers study glaciers decreased in area over the past century ranging between (1:24,000 scale). The USGS JFMAMJJASOND created these topographic maps QL = latent heat = 0.622 Au(ea-ei)ρ0 /P0 31% and 78%, an average of 51%. This range is assumed to be similar for the glacier where ρ is air density, cp is the specific heat capacity of air, A is a bulk The 1971-2000 climate norm modeled PRISM data was used population as a whole. Our simplified point energy balance model supports this idea. The from aerial photos taken between transfer coefficient (0.0015), and u is wind speed taken from nearby Tioga as climate input for the model. A moist adiabatic lapse rate modeled net balance for both lobes of Lyell Glacier are negative for the 1971-2000 climatic 1975 and 1984. Our inventory of Pass weather station. (Ta-Ti) and (ea-ei) is difference between air and was applied to each sample points (0.0065 °C m-1). glaciers and perennial ice features surface temperatures and water vapor pressure respectively (vapor pressure norm period, suggesting the glaciers are out of balance with the current climate. Future values from Marks et al, 1992). ρ /P is the atmospheric density at standard 0 0 climate scenarios suggest the Lyell East Lobe glacier will practically disappear by throughout the range yields over pressure. 800 features with an area greater 2050, while the Lyell West Lobe will continue to retreat. Encouraged by model results, we Melt estimates from the energy balance model were 2 4 plan to apply our energy balance model to a spatial model to more accurately model than 0.01 km , yielding a total area (! Darwin 2 3 West Lobe East Lobe compared to the 1967 summer balance data from of 34.8 km . Additionally, we (! topographic effects in other locations. Difficulties in local precipitation distribution need to be Goddard nearby Maclure Glacier. After winter snow identified over 800 ice features with resolved. accumulation was adjusted to measured data areas smaller than 0.01 km2. calculated summer melt matched measured. References Fu, P., and P.M. Rich, 1999. Design and implementation of the Solar Analyst: an ArcView extension for modeling solar radiation at Landscape Scales. Proceedings of the Nineteenth Annual ESRI User Conference, San Diego 3 Harrison, A.E., 1960. Exploring Glaciers- with a Camera. Sierra Club Books, San Francisco, CA, 71 pp. $ data IPCC, 2001. (Intergovernmental Panel on Climate Change). Climate Change 2001: The Scientific Basis, Contribution of Working Group I to the Third 2 model Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, UK, 944 pp. Klett, M., Manchester, E., Verburg, J., Bushaw, G. and Dingus, R., 1984. Second View: The Rephotographic Survey Project. Essay by Paul Berger. University of New Mexico Press, Albuquerque. 1 2 Leung, L. R., Y. Qian, X. D. Bian, W. M. Washington, J. G. Han, and J. O. Roads, 2004. Mid-century ensemble regional climate change scenarios for the (! Study Site ! 1 Lilliput ((! Picket western United States. Climate Change, 62, 75–113 Glacier 0 Mote, P.W., Hamlet, A.F., Clark, M.P. and Lettenmaier, D.P., 2005. Declining mountain snowpack in balance (m WEQ) (m balance western North America, Bull. of the Amer. Meteorology. Soc., 86:39-49. 0306015 Marks, D. and J. Dozier, 1992. Climate and energy exchange at the snow surface in the alpine region of the Sierra Nevada: 2. Snow cover energy balance, -1 Water Resources Research, vol. 28, num. 11, 3043-3054. Kilometers 345678910 Paterson, W. S. B., 1994. Physics of Glaciers, 3rd ed., Elsevier Science, Tarrytown, New York, 480 p. Local redistribution of snow by avalanching doubles PRISM Group, Oregon State University, http://www.prismclimate.org, created 4 Feb 2004 precipitation in avalanche runout areas for points 1,4, and 7. month Glacier regions of the Western US For more info on the glacier inventory visit: http://glaciers.us U.S. Geological Survey, Earth Science Photographic Archive.Online at http://libraryphoto.er.usgs.gov