Spatially distributed surface energy balance and ablation modelling on the ice cap of King George Island (Antarctica)

Unlike continental Antarctica, snow and ice melt is a significant component of the mass balance of glacial systems on the northern Antarctic Peninsula. Over several austral summers, a comprehensive field programme was conducted on the King George Island ice cap including the operation of three automatic weather stations and ablation measurements at different altitudes. These data were used to drive a spatially distributed energy balance model to investigate melt during the period from 2 December 1997 to 12 January 1998. Averaged over the study area (418 km2) and over this 6-week period, net radiation was found to be the main energy source (26 W m−2) followed by the sensible heat flux (8 W m−2). The latent heat flux was negative (−8 W m−2) indicative of sublimation. High melt rates prevailed during synoptic weather conditions associated with low or even reversed temperature lapse rates. However, little melting occurred during periods of high decrease in air temperature with increasing elevation (−0.8 to −1 K 100 m−1). These findings provide sufficient warning for the adoption of a constant lapse rate derived from averaged longer-term data which would significantly underestimate total melt due to underestimation of air temperatures at higher elevations during the periods when most melt occurs. Increasing air temperature by 1 and 2 K enhanced spatially averaged ablation by 27% and 62%, respectively, suggesting a high sensitivity to potential future climate warming in the area.