USING GIS TO ASSESS CLIMATIC AND TOPOGRAPHIC CONTROLS ON PERENNIAL SNOW IN THE SPRING MOUNTAINS, NEVADA

Recent discovery of till deposits in the Spring Mountains of southern Nevada indicates that this range held one or more glaciers during the late Pleistocene. Preservation of perennial snow is of key importance during onset of glaciation, and preservation of snow is a function of both regional climate and local topographic effects that produce microclimates. In this study we use a climate-driven snow and ice model called ELAPSE to explore the impacts of climate change on perennial snow in the Spring Mountains. There is reason to believe that the height and orientation of steep headwalls played an important role in the formation of Pleistocene glaciers. In July, 2002, the second year of a severe drought in the southwestern United States, we discovered snow preserved in the shadows of steep cliffs. In some cases this snowpack exceeded 3 meters in depth, although precipitation in the adjoining valley was only 1.8 cm in the preceding 12 months and only 0.25 cm in the preceding 7 months. GIS post-processing of ELAPSE solutions has been demonstrated to improve model results. We use ArcView GIS to determine landscape slope, curvature, and shading to find areas in which snow is likely to collect; these characteristics, along with an understanding of prevailing winds and avalanche patterns, allow us to better depict the spatial distribution of perennial snow under a variety of climate conditions. We present results demonstrating (1) the sensitivity of perennial snow to changes in temperature and precipitation and (2) the climate boundary conditions that produced late Pleistocene glaciers in the Spring Mountains.