The influence of large‐scale atmospheric circulation on the surface energy balance of the King George Island ice cap

Abstract

During the austral summer 1997-1998 three automatic weather stations were operated at different altitudes on the sub-Antarctic ice cap of King George Island (South Shetland Islands). Snowmelt was derived from energy balance computations. Turbulent heat fluxes were calculated from meteorological measurements using the bulk aerodynamic approach, with net radiation being measured directly. Modelled ablation rates were compared with readings at ablation stakes and continuously measured snow height at a reference site. Snow depletion and daily snowmelt cycles could be well reproduced by the model. Generally, radiation balance provided the major energy input for snowmelt at all altitudes, whereas sensible heat flux was a second heat source only in lower elevations. The average latent heat flux was negligible over the entire measuring period. A strong altitudinal gradient of available energy for snowmelt was observed. Sensible heat flux as well as latent heat flux decreased with altitude. The measurements showed a strong dependence of surface energy fluxes and ablation rates on large-scale atmospheric conditions. Synoptic weather situations were analysed based on AVHRR infrared quicklook composite images and surface pressure charts. Maximum melt rates of up to 20 mm per day were recorded during a northwesterly advection event with meridional air mass transport. During this northwesterly advection, the contribution of turbulent heat fluxes to the energy available for snowmelt exceeded that of the radiation balance. For easterly and southerly flows, continentally toned, cold dry air masses dominated surface energy balance terms and did not significantly contribute to ablation. The link between synoptic situations and ablation is especially valuable, as observed climatic changes along the Antarctic Peninsula are attributed to changes in the atmospheric circulation. Therefore, the combination of energy balance calculations and the analysis of synoptic-scale weather patterns could improve the prediction of ablation rates for climate change scenarios.

Recent Deceleration of the Ice Elevation Change of Ecology Glacier (King George Island, Antarctica)

“…It must be stressed that the mass balance of glaciers on King George Island is highly dependent on the large-scale circulation, mainly by advection of warm, humid air from the north [62]. Therefore, it is important to consider long term changes that are independent of the short-term fluctuations.…”

Climatic change on King George Island in the years 1948–2011

“…The air masses formed over the ocean and sea ice also affect the weather and climatic conditions of KGI (Schwerdtfeger 1975;Rogers 1983;Marshall and King 1998;Kejna 1999a, b;Marsz and Styszyńska 2000;Braun et al 2001). The pre− dominant type of air movement in the area of KGI is connected with western atmo− spheric circulation, constituting 70% (Kejna 1993).…”

Fluctuation of Glacial Retreat Rates in the Eastern Part of Warszawa Icefield, King George Island, Antarctica, 1979–2018

“…According to a simple ice dynamic model described by Knap et al [13], such conditions are likely to affect the glacial state of the King George Island ice caps. Moreover, there is evidence of a glacier mass balance deficit and increases in surface energy exchange in this region [11,14,15]. Most of the previous studies of glaciers retreat in ASPA-128 simply documented changes in the front positions of glaciers in different years on maps.…”