Energy balance estimates during the summer season of glaciers of the Antarctic Peninsula

Two small glaciers in Marguerite Bay on the west coast of the Antarctic Peninsula were chosen to monitor the accumulation and ablation pattern of the snow cover and the reaction of the glacial system in respect with global change. Both glaciers are located at 68°08′S and 67°06′W in the vicinity of the Argentine research base ‘San Martín’. McClary Glacier is a short valley glacier with an accumulation area not extending higher than 600 m asl. Its short snout joins the snout of Northeast Glacier to form an ice-cliff to the sea. Northeast Glacier is separated from McClary Glacier by a mountain ridge and is fed by a large ice-fall coming down from the plateau of the Antarctic Peninsula at 1500 m asl. As the topography of the glaciers in terms of accumulation area, length and surface elevation differs widely it is assumed that the glaciers react differently to climate variations. However the response time of these systems is believed to be of the same order of magnitude as the anticipated climatic variability. Therefore measures were taken to monitor the seasonal development of the snow cover on the lower parts of the glaciers in order to detect changes at an early stage. During the field campaign in the Austral summer 1994/1995 micro-meteorological measurements were carried out with automatic weather stations (AWS) at three locations on the glaciers. More than 40 snow pits were dug during the summer season to obtain data from the snow cover. Data was sampled on snow temperature variations, water equivalent, liquid water content, stratification of the snow cover, crystal types and crystal sizes. Furthermore the accumulation during the whole year from March 1994 to February 1995 was measured with stakes placed on the glaciers. The data from the AWS was used to compute energy available for ablation. This correlated well (r=0.9) with the changes observed in the snow pits. Turbulent heat fluxes account for 55% of the summer-time energy budget at the surface of the snow cover. Sensible heat is the dominant energy source for ablation during the summer. The equilibrium line was estimated between sea-level and 110 m asl. It is assumed that further warming will cause the development of an ablation zone on the two glaciers.