Evaporation over a glacial lake in Antarctica

Abstract

The study provides estimates of summertime evaporation over a glacial lake located in the Schirmacher oasis, Dronning Maud Land, East Antarctica. Lake Zub (alternately named Lake Priyadarshini and referred to throughout as Lake Zub/Priyadarshini) is the second-largest lake in the oasis, and its maximum depth is 6 m. The lake is also among the warmest glacial lakes in the oasis, and it is free of ice during almost 2 summer months. The summertime evaporation over the ice-free lake was measured using the eddy covariance method and estimated on the basis of five indirect methods (bulk-aerodynamic method and four combination equations). We used meteorological and hydrological measurements collected during a field experiment carried out in 2018. The eddy covariance method was considered the most accurate, and the evaporation was estimated to be 114 mm for the period from 1 January to 7 February 2018 (38 d) on the basis of this method. The average daily evaporation was 3.0 mm d−1 in January 2018. During the experiment period, the largest changes in daily evaporation were driven by synoptic-scale atmospheric processes rather than local katabatic winds. The bulk-aerodynamic method suggests the average daily evaporation is 2.0 mm d−1, which is 32 % less than the results based on the eddy covariance method. The bulk-aerodynamic method is much better in producing the day-to-day variations in evaporation compared to the combination equations. All selected combination equations underestimated the evaporation over the lake by 40 %–72 %. The scope of the uncertainties inherent in the indirect methods does not allow us to apply them to estimate the daily evaporation over Lake Zub/Priyadarshini. We suggested a new combination equation to evaluate the summertime evaporation over the lake's surface using meteorological observations from the nearest site. The performance of the new equation is better than the performance of the indirect methods considered. With this equation, the evaporation over the period of the experiment was 124 mm, which is only 9 % larger than the result according to the eddy covariance method.