melting ice sheets

The Thwaites Glacier in Antarctica—the so-called "Doomsday Glacier"—is in the news again. We are fascinated with it because it is the Godzilla of glaciers, 80 miles across and as massive as Florida. If the ice sheet holding it back were to melt, and if Thwaites plopped into the ocean, it would all by itself raise sea level two feet. It functions, however, to hold back other glaciers and ice formations, which in its absence would themselves head for the sea. If that happened you would be talking about ten feet of sea level rise. The last time I discussed it, Alastair G.C. Graham had just shown that glaciers sometimes move very quickly. This finding has been widely accepted by scientists.

B.E. Schmidt and colleagues write in a paper for Nature that scientists piloted an underwater vehicle beneath the ice shelf and the Thwaites glacier. Eat your heart out, James Cameron! They found that the glacier is melting a little slower than had been feared, but that since 2010 it has nevertheless shrunk consistently and fairly rapidly. Worse, much worse was their finding that there are big cracks in the glacier and terraced indentations from below that they call ‘staircase-like’ structures. These weak spots are exposed to relatively warm water, at a temperature of 2°C, i.e., 35.6°F, from beneath, and the glacier is melting especially rapidly at these weak hot points.