[imported_topaz1968]

Also there is an article entitled Recent Sea-Level Contributions of the Antarctic and Greenland Ice Sheets from the 16 March 2007 issue of Science (to which I am now subscribed, however you may only be able to read the abstract if you are not probably):

http://www.sciencemag.org/cgi/conten...;315/5818/1529

In the above article they present that they have found the Greenland and West Antarctic Ice Sheets are melting much faster than they can explain. The models do not use dynamics for these sheets that would allow them to melt as quickly as they are, and they are starting research to really understand the dynamics of what is happening. Here is the conclusion at the end of the article:

Implications for the Future

It is reasonable to conclude that, today, the EAIS is gaining some 25 Gt year–1, the WAIS is losing about 50 Gt year–1, and the GIS is losing about 100 Gt year–1. These trends provide a sea-level contribution of about 0.35 mm year–1, a modest component of the present rate of sea-level rise of 3.0 mm year–1. Because 50 Gt year–1 is a very recent contribution, the ice sheets made little contribution to 20th-century sea-level rise. However, what has also emerged is that the losses are dominated by ice dynamics. Whereas past assessments (47 ) considered the balance between accumulation and ablation, the satellite observations reveal that glacier accelerations of 20 to 100% have occurred over the past decade. The key question today is whether these accelerations may be sustained, or even increase, in the future.

The question is difficult because the causes of the instabilities have yet to be established. The geological record (48 ) suggests that some 10,000 years ago, the Amundsen sector of the WAIS extended only 100 km farther than today, confining the present rate of retreat to more recent times, and the drawdown of the Amundsen sector ice streams has been linked (49) to a recent trigger in the ocean. A comparable argument may be extended to the thinning glaciers in East Antarctica and Greenland, which are also marine terminated. Equally, there is no direct evidence of a warming of the Amundsen Sea, and it has long been held possible that the marine-terminated WAIS, and the Amundsen sector in particular, may be geometrically unstable (50), and the retreating East Antarctica streams have a similar geometry (Fig. 2A). In Greenland, where summer melting is widespread and increasing, Global Positioning System measurements have shown the melting to affect flow velocity in the ice sheet interior (26), introducing the possibility that increased surface meltwater is reaching the bed and accelerating the ice flow to the ocean.

The discovery that particular ice streams and glaciers are dominating ice sheet mass losses means that today our ability to predict future changes is limited. Present numerical models capture neither the details of actual ice streams nor, in Greenland, those of hydraulic connections between the surface and the bed. In addition, the detailed mechanics at the grounding line still remain to be fully worked out. In consequence, the view that the changing sea-level contribution of the Antarctic and Greenland ice sheets in the 21st century will be both small and negative as a result of accumulating snow in Antarctica [e.g., –0.05 mm year–1 in (1)] is now uncertain. Because our predictive ability is limited, continued observation is essential. The satellite record clearly identifies the particular ice streams and glaciers whose evolution is of greatest concern. The causes of their instability need to be identified. Their detailed basal topography, their basal hydrology, and the details of the interaction with their surrounding shelf seas need to be established. Numerical models that capture the detailed dynamics of these glaciers and their hydrology are required. Of equal importance are meteorological and ice core measurements that will increase confidence in forecast models of accumulation and ablation fluctuations, because to a considerable extent these limit interpretations of the short satellite records. There is a great deal that the International Polar Year may achieve.