The Ice Sheets around Antarctica expand during the Southern Winter (i.e. our summer) and then contracts during the Southern Spring and Summer (i.e October to about March 22, but the effect may last till early April). What this means is the most likely time for a break in the Ice Shelf is when it is at its smallest after a long hot (for Antarctica) Summer. Thus the most likely date is March 2007 (or March 2008 or any subsequent march). The breakup may occur earlier or even as late as early April (Do to increase cold weather water that had melted during the Summer may freeze and break the Ice Shelf up, but this is only when the Ice Shelf is at its minimum, once the Ice Shelf starts to expand we are safe for another year).
Remember the West Antarctic Ice Sheet (WAIS) is grounded BELOW Sea Level, thus if it breaks up the ice stored in the WAIS will raise world wide sea levels about Five meters (Or about 20 feet). The Ross ice Sheff floats on sea ice and as floating ice it has already displaced the water it will become when it melts. Thus the Ross Ice Sheff will have no (or very little effect) on World wide sea levels.
The Big Concern is if the Ross Ice Sheff collapse, the WAIS follows it in rapid collapse for the base of the WAIS is BELOW sea level, thus ocean water directly affects the WAIS. If the Ice Sheff goes, the protective cover over the Southern ocean interface with WAIS would be gone, permitting the water to become warmer than at present, leading to rapid collapse.
Another fear is if the Ice Sheff goes, it will take the WAIS with it as one big break up of floating ice, thus not a two step disaster but one step.
Now the Greenland Ice Sheet is grounded ABOVE sea level, thus the ocean has NO direct affect on the Greenland Ice Sheet and as such is viewed as "stable" i.e. it might melt, but it will not collapse in a single moment of disaster. Present estimates is the Greenland ice sheet will take 50 years to melt and raise world wide ocean levels about 5 meters. Notice this is a SLOW process, unlike the instantaneous disaster the WAIS may become.
Now the biggest Ice Sheet is the East Antarctic Ice Sheet (EAIS). If it should melt, world wide ocean levels can raise as much as 70 meters. 70% of the Fresh water on this plant is in the EAIS (With the WAIS having little over 10% and the Greenland Ice Sheet a little less than 10 % the rest in the lakes, Rivers and Glaciers in the rest of the world). The EAIS is considered Stable and may even EXPAND do to global warming (Higher temperatures, more snow reaching EAIS, thus adding more ice to the EAIS than melted away to floats away as Ice Bergs. The reason for this is the EAIS is Completely within the Antarctic Circle AND is grounded on solid land (Antarctica has the highest Average attitude of any Continent, it is in fact the TALLEST Continent, this height means the EAIS has little or no contact the Southern Ocean that surrounds Antarctica).
Thus the concern is NOT the EAIS or even Greenland, but the WAIS. It is unstable being grounded on the sea floor for West Antarctic is a series if Islands thar only appears solid do to the ICe Sheet. Being grounded on land the WAIS is directly affected by the temperature of the Ocean and thus unstable.
It is believed that 120,000 years ago the WAIS did collapse producing the "Mad house Century" the preceded the last Ice Age. For more see:
http://www.imaja.com/as/environment/can/journal/madhousecentury.htmlhttp://home.earthlink.net/~icedneuron/CCLinks.htm
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