Climatology and ablation at the South Greenland ice sheet margin from automatic weather station observations

Abstract. We describe the climatology from a meteorological dataset acquired from automatic weather station observations done in the ablation zone of the Greenland Ice Sheet between 2001 and 2007. Stations were placed in three regions below the polar circle: on the southern tip of the ice sheet, on a calving glacier in the Nuuk fjord, and on the south-eastern ice margin near Tasiilaq. The yearly cycles in temperature, relative humidity and wind speed reveal the largest variability in wintertime, causing annual values to depend largely on winter values. Adding to wintertime variability are extremely strong and cold katabatic wind events in the southeast ("piteraqs"). During summer no pronounced daily cycle in near-surface atmospheric parameters is recorded in the three regions, in spite of a large cycle in solar radiation, dominantly regulating surface melt. Net ablation is largest at the southernmost station due to low surface albedo, and can be up to six metres per year, but is highly sensitive to the timing of the start of the ice ablation season. Illustrative of this is that similar ablation amounts are found in the Nuuk fjord region where little or no snow accumulates in winter.