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Surface Mass Balance of Antarctica
Reference
Van de Berg, W.J., van den Broeke, M.R., Reijmer, C.H. and van Meijgaard, E. 2006. Reassessment of the Antarctic surface mass balance using calibrated output of a regional atmospheric climate model. Journal of Geophysical Research 111: 10.1029/2005JD006495.

What was done
The authors carried out a detailed quantitative evaluation of model-simulated Antarctic surface mass balance (SMB) for the period 1980 to 2004, including solid precipitation, sublimation and snowmelt, after which they calibrated the model so its results would match observations, "in order," as they put it, "to get a best possible estimate of the contemporary Antarctic SMB" that "provides a new estimate of the SMB where few observations are available."

What was learned
Van de Berg et al. report that compared to the latest SMB compilation, calibrated model-simulated SMB is up to 1 m yr-1 higher in the coastal zones of East and West Antarctica in areas with few observations, which leads to the result that the SMB integrated over the grounded ice sheet (GIS) exceeds previous estimates by as much as 15%. Specifically, they say that "the calibrated SMB equals a total mass input to Antarctica of 2.08 0.03 x 1015 kg yr-1 for the GIS and 2.52 0.03 x 1015 kg yr-1 for the whole of Antarctica including ice shelves." These values, as they continue, "are higher than all estimates listed by IPCC (2001, p. 651)," although they say "they are comparable with the recent model estimate from Bromwich et al. (2004)." Finally, they note that "the increase of the SMB compared to the IPCC estimate represents an additional storage of water on Antarctica of 0.6 mm global sea level yr-1." And they add that "the only method to validate or disprove these results is to perform more SMB measurements in coastal areas of Antarctica."

What it means
Unless other and newer data eventually prove otherwise, it would appear that the surface mass balance of the whole of Antarctica from 1980 to 2004 likely was positive, and that the continual buildup of snow and ice on the continent has had a tendency to lower mean global sea level.

References
Bromwich, D.H., Guo, Z., Bai, L. and Chen, Q.-S. 2004. Modeled Antarctic precipitation. Part I: Spatial and temporal variability. Journal of Climate 17: 427-447.

Intergovernmental Panel on Climate Change. 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group 1 to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, New York, NY.

Reviewed 25 October 2006