Thermal Dynamics of the Active Layer Along a Hydrologic Gradient Bordering Lakes in the McMurdo Dry Valleys, Antarctica

With little precipitation (<10 cm water equivalent annually as snow), soils of the McMurdo Dry Valleys (MDV) have limited water available to support hydrological or biogeochemical processes. Active layer depths across most of this landscape are <1 m. Saturated sediments are obvious in wetted margins on the shorelines of lakes, extending for up to ~10 m into a zone where typically arid MDV soils prevail. We propose that wetted margins of MDV lakes will differ from arid soils across the rest of the landscape in their active layer depth and temperature regimes because of the consistent presence of water within these wetted margins. We have monitored temperatures along a wetted margin of Lakes Fryxell, Bonney, and Joyce. During the austral summer, we found that drier soils promoted shallower thaw depths and that, at the same depths, wet soils generally had lower temperatures and smaller diurnal fluctuations than dry soils.