Assessing uncertainties of evaporation over glacial lakes in Antarctica

Lakes play a significant role in the global water cycle and influence regional and local weather patterns. They influence local moisture fluxes by providing a constant moisture source to the atmosphere through evaporation, which is difficult to measure. Therefore, indirect methods needing only a few meteorological and hydrological observations are applied in evaluation of evaporation over lakes. In Antarctica, many well known indirect methods tend to underestimate the summertime evaporation over the lakes. This study quantified the uncertainties of the bulk-transfer equations applying to estimate the summertime evaporation over glacial lakes in Antarctica. We used the eddy-covariance (EC) method to provide a reference while evaluating the uncertainties in the bulk-transfer methods applied to estimate daily evaporation over two glacial lakes. The micrometeorological observations of near surface air temperature, wind speed, wind direction, atmospheric pressure, water vapor concentration were collected in the Schirmacher oasis (Dronning Maud Land, East Antarctica) during two austral summers (DJF) 2017-2018 and 2019-2020. Our results show that the summertime evaporation over the glacial lakes 3.0 mm per day on average during the ice-free period, and it is 1.6 mm per day over the ice break-up period. The best indirect method was the bulk-aerodynamic method which underestimated the evaporation over the lakes by 32 %. Changes in evaporation over the lakes was associated with changes in wind speed rather than changes in near surface air temperature, and the changes in wind speed were driven by variations in synoptic scale flow patterns, which the largest changes in daily evaporation.