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Surface Mass Balance of the Greenland Ice Sheet
Ettema, J., van den Broeke, M.R., van Meijgaard, E., van de Berg, W.J., Bamber, J.L., Box, J.E. and Bales, R.C. 2009. Higher surface mass balance of the Greenland ice sheet revealed by high-resolution climate modeling. Geophysical Research Letters 36: 10.1029/2009GL038110.

The authors write that "to better quantify and predict the mass balance and freshwater discharge of the Greenland Ice Sheet requires improved knowledge of its surface mass balance (SMB)," which is "the annual sum of mass accumulation (snowfall, rain) and ablation (sublimation, runoff)."

What was done
Ettema et al. applied a regional atmospheric climate model over a domain that includes the Greenland Ice Sheet and its surrounding oceans and islands at "unprecedented high horizontal resolution (~11 km)," which for use over Greenland was coupled to a physical snow model that treats surface albedo as a function of snow/firn/ice properties, meltwater percolation, retention and refreezing. The atmospheric part of the model was forced at the lateral boundaries and the sea surface by the global model of the European Centre for Medium-Range Weather Forecasts for the period September 1957 to September 2008.

What was learned
The modeling work of the seven scientists, as they describe it, showed "total annual precipitation in the Greenland ice sheet for 1958-2007 to be up to 24% and surface mass balance up to 63% higher than previously thought," with the largest differences occurring in coastal southeast Greenland, where they say "the much higher resolution facilitates capturing snow accumulation peaks that past five-fold coarser resolution regional climate models missed."

The total ice sheet's SMB averaged over the entire study period was 469 41 Gt per year; and before 1990 none of the mass balance components exhibited a significant trend. Since 1990, however, there has been a slight downward trend in Greenland's SMB of 12 4 Gt per year, which is probably not all that significant, considering the fact that over the one-year-period 1995 to 1996 its SMB rose by a whopping 250%.

What it means
With respect to the stability/longevity of the Greenland Ice Sheet, Ettema et al. state that "considerably more mass accumulates on the Greenland Ice Sheet than previously thought, adjusting upwards earlier estimates by as much as 63%," which suggests that the Northern Hemisphere's largest ice sheet may well hang around a whole lot longer than many climate alarmists have been willing to admit.

Reviewed 19 August 2009