Reduced Albedo and Accumulation Contribute to Negative Surface Mass Balance of the Greenland Ice Sheet

The year 2010 saw a large increase in near-surface temperatures along the coast of the Greenland ice sheet (GrIS); consequently, these unusually warm surface temperatures led to a huge increase in surface melting over the GrIS. To further explore this phenomenon, Tedesco et al. (2011) used data from satellite sensors, surface glaciological observations and regional atmospheric models to study the surface albedo, accumulation and the number of days bare ice was exposed over the GrIS in 2010. Their results indicated that the high near-surface temperatures over the GrIS led to a strongly negative surface mass balance—defined as the difference between accumulation and ablation of ice and snow—which was further intensified by the decrease in albedo and the increase in the number of days bare ice was exposed in the GrIS. Thus, the authors concluded that these anomalous conditions led to a longer melting season and contributed to the strongly negative surface mass balance of the GrIS in 2010.
Tedesco, M., Fettweis, X., van den Broeke, M. R., van de Wal, R. S. W., Smeets, C. J. P. P.,  van  de Berg, W. J., Serreze, M. C., Box, J. E. 2011. The role of albedo and accumulation in the  2010 melting record in Greenland. doi:10.1088/1748-9326/6/1/014005

In large areas of the ablation zone in the south of the GrIS, the melting season had started 50 days earlier than the average melting season (measured from 1979 to 2009) and had ended exceptionally late in 2010. While the increase in surface melting can be positively correlated with the increase in near-surface temperatures, recent studies have shown that the melting of the GrIS also depends on the accumulation, radiation, and refreezing and sublimation conditions. The surface mass balance is also strongly correlated with albedo because when melting increases, the grain size of the snow increases and which consequently, decreases the albedo. In this study, the authors used moderate-resolution imaging spectroradiometer (MODIS) albedo product to study anomalies in albedo; they also used data from automatic weather stations and regional surface and energy models to study the surface mass balance anomalies in 2010. They found the largest negative albedo anomalies occurred  in August along the south west coast of the ice sheet; they hypothesized that the reduced amount of snowfall, enhanced melting and increased number of bare ice exposure days could have led to the 2010 albedo anomalies. While the early melt season was triggered by the large increase in near-surface temperatures, the reduced accumulation and albedo were more likely to be responsible for the premature bare ice exposure. Thus, the authors inferred that the anomalously warm conditions reduced the accumulation and albedo, which led to the strongly negative surface mass balance of the GrIS in 2010.

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