First, the bad news:
For years scientists have pointed to the instability of the Western Antarctic as posing the greatest immediate potential threat of rising seas. A 1998 study published in Nature suggested sea rise could amount to 4-6 meters assuming warming trends in the ocean surrounding the Western Antarctic continued their relentless increase. A new study, however, suggests that the Eastern Antarctic, containing far more ice than its smaller Western counterpart, is now at risk.
East Antarctica is widely considered to be more stable than the West Antarctic ice sheet but a study suggests that a large region of the eastern ice sheet is in danger of becoming irreversibly unstable once a relatively thin section of retaining ice on its coast is lost, the researchers said.Matthias Mengele of the Potsdam Institute for Climate Research in Germany likens the Wilkes Basin in Eastern Antarctica to a tilted bottle filled with water. The "cork" in this case (the ice plug formed by bedrock underlying the Wilkes basin) is far smaller than the amount of ice it keeps in. Uncork it and the contents begin to spill out. Mengele is the lead author of a recent study published in the journal Nature Climate Change :
A slab of coastal ice is all that is stopping the giant Wilkes Basin ice sheet from slipping into the sea. Once this process begins it will relentlessly continue to pour vast amounts of water into the oceans for centuries to come, raising global sea levels by between 3-4m, they said.
East Antarctica holds around a 10-times-greater volume of ice than West Antarctica. Much of the ice in the east lies at high altitude and is kept well below freezing point, but a large proportion of it - enough to raise sea levels by 19m - lies on bedrock that is below sea level, such as the Wilkes Basin.The bad news is that once this process starts--once the "cork" has been popped--the process is irreversible. Mengele's study showed through computer modeling that once the "plug" formed by the ice and bedrock in the Wilkes basin is eroded through rising ocean temperatures, the vast amount of ice "held in" begins to contact the ocean and continues to melt....and melt...and melt:
Scientists had considered even this low-lying part of the East Antarctic ice sheet - the so-called marine ice sheet - to be more stable and less likely to disintegrate in a warmer climate than the marine ice sheet of the West Antarctic. However, analysis of the bedrock on which the marine ice sheet of Wilkes Basin stands suggests this is not the case. Scientists found that the rock becomes a raised ridge at the coast which allows the ice to form a protective plug between the ocean and the ice sheet.
Melting would make the grounding line retreat – this is where the ice on the continent meets the sea and starts to float. The rocky ground beneath the ice forms a huge inland sloping valley below sea-level. When the grounding line retreats from its current position on a ridge into the valley, the rim of the ice facing the ocean becomes higher than before. More ice is then pushed into the sea, eventually breaking off and melting. And the warmer it gets, the faster this happens.Mengele's study can be found here.
In total the Antarctic ice shelf contains enough ice to raise sea levels from 50-60 meters, enough to submerge the building that houses Fox News in Manhattan, among others.
Coastal cities, several U.S. states, populations, and many islands, of course, would be inundated. Washington DC would likely become a water park.
The good news is that the process will take several centuries. The study found it may take as many as 200 years for the "cork" to melt, with the outflowing and subsequent melting of all of the trapped ice taking several thousands of years.
That is taking into account current estimates of rising ocean temperatures. Unfortunately the estimates of the rate of melting for the Western Antarctic weren't exactly accurate the first time around. Remember that 1998 study? It was updated fairly recently:
In 2012, another paper said that temperatures in the West Antarctic had risen dramatically more than scientists had earlier thought — 4.4 degrees since 1958. Then just last month, more bad news hit: The West Antarctic is shedding ice at a faster rate than ever, with six regional glaciers disgorging roughly as much ice as the entire Greenland ice sheet.So no one should be "popping corks" to celebrate just yet.