DECADAL CHANGES IN HEAT CONTENT, ICE THICKNESS, AND HEAT EXCHANGE OF ICE-COVERED LAKES OF TAYLOR VALLEY, ANTARCTICA

Lakes integrate landscape processes and climate dynamics over timescales of days to years. Most of the permanently ice-covered lakes in the McMurdo Dry Valleys, Antarctica are closed-basin, receiving glacial melt water from streams for 8-12 weeks per year. Lake level rises during the austral summer are balanced by sublimation of ice covers year-round and evaporation of open water moats also in the austral summer. Vertical profiles of water temperature have been measured in three lakes in Taylor Valley since 1988. From these data, measurements of lake level change, and lake hypsometry, calculated heat contents indicate that these three lakes have been gaining heat since the mid-2000s. Since 2002, lake levels have risen substantially (as much as 2.5 m), and ice covers have thinned (1.5 m on average). The recent increases in heat content are occurring on rates more than twice the heat content losses of the 1980s-1990s. Analyses of lake ice thickness, meteorological conditions, and stream water heat loads indicate that the main source of heat to these lakes is from latent heat released when ice-covers thicken during the winter. Additionally, water inflows to the lakes have been of cool water (cooler than streamflow is typically) lately, suggesting increased direct inflow from glaciers. These results indicate that McMurdo Dry Valley lakes are sensitive long-term indicators of climate processes in this polar desert landscape.