RECENT ICE LOSS RATES OF A SMALL VALLEY GLACIER IN DENALI NATIONAL PARK AND PRESERVE, ALASKA

Alpine glaciers make up a small portion of global land-based ice when compared to the Greenland and Antarctic Ice Sheets, but they contribute a significant percentage to estimates of current and projected sea level rise. A recent study in Alaska processed airborne altimetry data collected from over 100 glaciers and found a negative average mass balance for the past 19 years of the region. Alaska’s Denali National Park and Preserve currently contains ~4,000 km² of glacial ice. Glaciers are integral components of the hydrologic, ecologic, and geologic systems of Alaska and Denali. Tracking change is important to analyze patterns of climate warming in Alaska and its effects on components of Denali’s ecosystem. This study determined surface elevation change rates for the Middle Fork Toklat glacier located on the North side of the Alaska Range in Denali National Park and Preserve. This glacier is indicative of the smaller, relatively low elevation glaciers in Denali National Park. The Middle Fork Toklat glacier has retreated enough to recently separate into distinct east (4.3 km²) and west (3.5 km²) branches. Glacier surface elevations were obtained during the summer of 2015 using survey grade Trimble R6 and mapping grade Geo7X GPS systems. Glacier surface elevation GPS data were compared to a 2010 IFSAR digital elevation model and a photogrammetry based 1952 digital elevation model in order to asses changes in glacier surface loss rates through time. Our results reveal a 38% increase in average surface elevation thinning rates for the Middle Fork Toklat glacier for the period 1952-2010 to 2010-2015.