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Mass Balance of the Antarctic Ice Sheet
Remy, F. and Frezzotti, M. 2006. Antarctica ice sheet mass balance. Comptes Rendus Geoscience 338: 1084-1097.

The authors note that "each year, about 2200 gigatonnes of snow fall on the Antarctic ice sheet and sink toward deeper layers, where it slowly changes into ice," which ice "then flows toward the coast, where the same quantity of ice is rejected to the ocean much later," noting further that "this annual balance corresponds to 6.5 mm of sea level, so that a slight imbalance may have an impact on sea-level change."

What was done
To get a better feel for the current status of the mass balance the Antarctic Ice Sheet and what we might expect to occur in the near and far future, Remy and Frezzotti reviewed "the results given by three different ways of estimating mass balance, first by measuring the difference between mass input and output, second by monitoring the changing geometry of the continent, and third by modeling both the dynamic and climatic evolution of the continent."

What was learned
Quoting the conclusions of the two researchers, "the East Antarctica ice sheet is nowadays more or less in balance, while the West Antarctica ice sheet exhibits some changes likely to be related to climate change and is in negative balance." In addition, they report that "the current response of the Antarctica ice sheet is dominated by the background trend due to the retreat of the grounding line, leading to a sea-level rise of 0.4 mm/yr over the short-time scale," which they describe in terms of centuries. However, they note that "later, the precipitation increase will counterbalance this residual signal, leading to a thickening of the ice sheet and thus a decrease in sea level."

What it means
Although there is a potential for short-term climatic fluctuations to either increase or decrease the water equivalent of the Antarctic ice sheet and, thereby, correspondingly impact global sea level, there is as yet no conclusive evidence that the huge ice sheet covering East Antarctica is being affected to any significant degree, especially in the way suggested by climate alarmists, i.e., excessive mass loss that raises sea level. Recent analyses of global sea level trends also support this conclusion (Jevrejeva et al., 2006; Holgate, 2007). In fact, they suggest there may well have been a slight decrease in the rate-of-rise of the world's oceans over the 20th century, possibly indicating a net positive Antarctic ice sheet mass balance over this period.

Holgate, S.J. 2007. On the decadal rates of sea level change during the twentieth century. Geophysical Research Letters 34: 10.1029/2006GL028492.

Jevrejeva, S., Grinsted, A., Moore, J.C. and Holgate, S. 2006. Nonlinear trends and multiyear cycles in sea level records. Journal of Geophysical Research 111: 10.1029/2005JC003229.

Reviewed 31 January 2007