The effect that the expansion of warming ocean water has on sea level is easy to predict. You just plug the value for a given amount of warming into a physical calculation. The contributions from melting glacial ice, however, are much trickier to divine. It depends heavily on fine-scale details, like the shape of the surface beneath the ice, which controls the glacier’s flow toward the sea.
Those fine-scale details aren’t easy to come by—not least because of the difficulty of accessing what can be remote and frigid places. While it’s expensive, field work can fill in key unknowns and reveal some of these glaciers’ histories, informing our estimates of future behavior.
The East Antarctic Ice Sheet isn’t as fragile as its western counterpart, but it is much, much larger. The biggest individual outlet glacier for East Antarctic ice is the Totten Glacier. On its own, the ice behind Totten could raise global sea level more than three meters if it were to melt completely. These frozen giants are generally slow to stir, but like most glaciers around the world, Totten is shrinking. The large floating ice shelf in front of Totten, which holds back the flow of ice like a buttress, is thinning at a rate in the neighborhood of 10 meters per year.