Ice ablation and meteorological conditions on the debris covered area of Baltoro Glacier (Karakoram, Pakistan)

During the recent Italian expedition ‘K2 2004 –50 years later ’(June –July 2004)on Baltoro glacier,Karakoram,Pakistan,glaciological field experiments were carried out on the debris-covered area of this high-elevation glacier.The aim was to investigate the ice ablation and its relations with debris thermal properties and meteorological conditions.Ablation measurements along the glacier up to about 5000 m and within a dedicated test field were combined with meteorological data from two automatic weather stations located at Urdukas (4022 ma.s.l.)and at K2 Base Camp (5033 ma.s.l.).In addition,temperature measurements of the debris cover at different depth levels along the glacier allowed the calculation of debris surface temperature and of the debris thermal resistance (R ).Using the air temperature,the local mean lapse rate (0.0075 8 Cm –1 )and the measured ablation,the degree-day factors (K )at different locations on the glacier were calculated.The ice ablation rates were related to debris thickness and elevation.They are typically on the order of 4 cm d –1 during the observation period. However,it was found that the surface topography (slope,aspect)has an influence on the total ablation similar to that of the debris thickness.Thermal resistance of the debris cover and its distribution over the glacier were estimated.Finally,a best-guess estimate of the total meltwater production was calculated from available climate data.