Лëд и снег (Sep 2022)
Summer mass balance of the Bellingshausen Dome on King George Island, Antarctica
Abstract
For the first time the summer mass balance of the Bellingshausen Ice Cap, the King George Island (Water-loo) in Antarctica, was estimated for the period of summer seasons 2007–2012 and 2014–2020. Measurements were carried out over a network of 29 ablation stakes. The contribution to the summer mass balance on the dome includes melting of snow (77%), glacial ice (15%), and superimposed ice (8%). Altitude gradients of snow and ice melting on slopes of different exposition were determined, which changed from –1.5 mm of water equivalent (w.e.) per 1 m on western slope in years with annual positive ice mass balance to –11 mm w.e. per 1 m on southern slope in years with negative ice mass balance. The summer mass balance on the cap was calculated using: 1) the average summer air temperature; 2) the sum of positive daily temperatures from data of the Bellingshausen weather station, 3) sum of average monthly air temperatures. Based on a comparison of colder (2009/10) and warmer (2019/20) years, the average melting coefficient for snow and ice for the glacier was calculated to be 9.5 mm/°C per day (Day Degree Factor – DDF). The high value of the DDF is probably due to intensive summer condensation during periods of frequent foggy weather on King George Island. A good correlation was found between the summer mass balance on the cap and the average summer air temperature at the Bellingshausen weather station for December–March (R2 = 0.9). This shows that the air temperature is the decisive factor of the change in the summer mass balance. Using this correlation, the dynamics of the summer mass balance on the cap was restored for the observation period (1969– 2020), which approximately corresponds to the trends in the annual mass balance on the cap. According to observations, it was found that positive deviation of the average summer air temperature by 0.5 °C from its climatic average value (~1 °C) increases the summer mass balance by 56%, while its negative deviation by 0.5 °C decreases the summer mass balance by 36%. This demonstrates a very high sensitivity of the summer mass balance on the glacier cap to climate changes.
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