Summertime evaporation over two lakes in the Schirmacher Oasis, East Antarctica

Abstract. Amount of liquid water has been continuously grown in coastal Antarctica. It accumulated in the hydrological system including rivers and lakes existing both on ice surface and inside it. This complex hydrological system is poorly understood and it is challenging without comprehensive measurements of components of hydrological balance. This study focused on lake evaporation which were measured directly on two lakes located in the Schirmacher Oasis (70° S, Antarctica) with the eddy-covariance (EC) technique. The experiment lasted during two austral summers (December–February) in 2017–2018 and 2019–2020. The lakes were warmer than ambient air during whole summers, and they became ice free for the period of 3–6 weeks. The measurements showed that summertime evaporation varied from 0.3 to 5.0 mm d−1, and depending on the ice cover presence, the average evaporation ranged from 1.5±0.1 mm d−1 in December to 3.0±0.2 mm d−1 in January–February. The EC measurements were used as a reference for evaluating uncertainties of five empirical formulas and bulk-aerodynamic method implementing various turbulent transfer coefficients. The bulk-aerodynamic method with locally adjusted turbulent transfer coefficients shows the most accurate estimates of daily rates of the lake evaporation (of 6 %–8 %). The empirical formulas underestimated the seasonal rate of lake evaporation by 27 %–73 %. Our results indicate that wind speed is the primary factor that controls summertime evaporation over the lakes. The largest day-to-day variations in evaporation were associated with changes in the wind speed.