East Antarctica (and West)

A study published in Nature Climate Change concludes that additional warming of just 1 to 2.5 degrees Celsius above the current global mean temperature would melt an "ice plug" in Wilkes Basin.  This would start an irreversible ice flow causing a sea level rise of 3 to 4 meters over several thousand years.

Update (May 12):  Studies published in Science and Geophysical Research Letters point to rapid melting in West Antarctica.  The Thwaites glacier is in early stages of collapse with eventual total collapse almost certain.  Warmer water melts the underside of the glaciers causing a retreat of the grounding-line.  The New York Times reports that a 3 meter sea level rise seems inevitable.

Update (May 13):  Joe Romm says news reports are underplaying the seriousness of these new reports. He quotes Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research:

What climate scientists have feared for decades is now beginning to come true: We are pushing the climate system across dangerous tipping points. Beyond such points things like ice sheet collapse become self-sustaining and unstoppable, committing our children and children's children to massive problems. The new studies strongly suggest the first of these tipping points has already been crossed. More tipping points lie ahead of us. I think we should try hard to avoid crossing them.

Update (May 19):  More about Antarctic ice losses.  And the potential loss in Greenland is also worse than previously believed.

Update (May 21):  More about Greenland and Antarctica, and a reminder of a 2012 paleoclimate report, quoting lead author Kenneth Miller of Rutgers University:

The natural state of the Earth with present carbon dioxide levels is one with sea levels about 70 feet higher than now.

Update (July 7):  A study from the University of New South Wales shows that warmer water is displacing cooler water near the Antarctic coast and will likely accelerate ice sheet melting.

Update (August 21):  A study from the Alfred Wegener Institute used satellite measurements to determine that the Greenland and Antarctic ice sheets are melting at a combined rate of 500 cubic kilometers per year. That is twice as fast as just five years ago.

Update (August 23):  A study lead by the Potsdam Institute for Climate Impact Research says warming in Antarctica could become the largest contributor to sea level rise adding up to 37 centimeters by 2100.

Update (October 19):  Joe Romm reports on studies indicating that "worse case scenarios" for sea level rise have been underestimated.

Update (December 16):  New studies indicate that the melting and/or collapse of the West Antarctic and Greenland ice sheets could happen faster than previously estimated.

Update (July 17, 2015):  A study published in Geophysical Research Letters says that Greenland's fjords are deeper than previously known which could lead to faster melting of the outlet glaciers.

Update (May 19, 2019):  A study published in Geophysical Research Letters analyzes 25 years of data from Antarctica.

While the majority of the ice sheet has remained stable, 24% of West Antarctica is now in a state of dynamical imbalance. Thinning of the Pine Island and Thwaites glacier basins reaches 122 m [400 ft] in places, and their rates of ice loss are now five times greater than at the start of our survey.