Summertime evaporation over glacial lakes in the Schirmacher oasis, East Antarctica.

The summertime evaporation over a large shallow lake located in the Schirmacher oasis, Dronning Maud Land, Antarctica. Lake Zub/Priyadarshini is the second largest lake in the oasis,  its maximum depth is  6 m. The lake is among the warmest lakes, and it is free of ice during almost two summer months. The summertime evaporation over the water table of the lake was estimated after the eddy covariance (EC) method, the bulk aerodynamic method and Dalton type empirical equations. We used special meteorological and hydrological measurements collected during the field experiment carried out in 2018 in addition to the standard observations at the nearest meteorological site. 

The EC method was considered as the most accurate given a reference for other estimates of evaporation over the lake water surface. We estimated the evaporation over the ice free lake surface as 114 mm in the period from 1 January to 7 February 2018 (38 days) after the direct EC method. The average daily evaporation is estimated to be 3.0 mm day-1 in January 2018. The largest changes in the daily evaporation were driven by the synoptic-scale atmospheric processes rather than local katabatic winds. 

The bulk aerodynamic method suggests the average daily evaporation to be 2.0 mm day-1 , and it is over 30 % less than the EC method. This method is much better in producing the day-to-day variations in evaporation compared to the Dalton type semi-empirical equations, which underestimated the evaporation over the lake open water table for over 40–72 %. We also suggested a linear empirical relationship to evaluate the summertime evaporation of Lake Zub/Priyadarshini from the observations at the nearest meteorological site and surface water temperature. After this method, the evaporation over the period of the experiment is 120 mm, and it is only 5 % larger than the result according to the EC method. We also estimated the daily evaporation from the ERA5 reanalysis, which suggested the average daily evaporation during austral summer (December – February) 2017–2018 to be 0.6 mm day-1. It is only one fifth of the evaporation estimated with the direct EC method. 

The poster shows the results which were obtained together with Timo Vihma and Tuomas Naakka (Finnish Meteorological Institute, Helsinki, Finland), Miguel Potes (Institute Earth Science, Evora, Portugal), Pankaj Ramji Dhote and Praveen Kumar Thakur (Indian Institute of Remote Sensing, Dehradun, India). The study was funded by the Academy of Finland (contract number 304345) and the COST Snow Action ES1404. The measurement campaigns were supported by the Finnish Antarctic Research Program, the Russian Antarctic Expedition, and the Indian Antarctic expedition.