A sobering report from University of Delaware researcher Andreas Muenchow today:
“In the early morning hours of August 5, 2010, an ice island four times the size of Manhattan was born in northern Greenland.”
The ice island calved from the Petermann Glacier, which has so far lost about 25 percent of its 43-mile floating ice shelf, according to a University of Delaware press release. The ice island covers at least 100 square miles and is up to half the height of the Empire State Building in thickness.
Ice shelves consist of floating ice that extends out toward sea from glaciers. When chunks break off, they do not contribute to sea level rise by themselves, just as an ice cube melting in a full glass of water does not cause the water to overflow. But ice shelves still are significant because they can hold back the flow of a glacier into the ocean. And when a glacier calves more ice into the sea, it does contribute to sea level rise, just as dropping an ice cube into a full glass of water will cause it to overflow.
Ice shelves are the most vulnerable part of the ice sheets. Waves and currents buffet the edges. Large chunks calve off, creating icebergs. But according to Bindschadler, ice shelves also help stabilize the ice sheet. Because the edges are often partially grounded in shallow water, ice shelves hold back the glaciers that feed them. When an ice shelf retreats or collapses, as some are doing now, the breaks are removed. The glaciers behind it speed up and drain more ice into the ocean. The loss of ice now outpaces the creation of new ice, and the ice sheet shrinks. When the Larsen-B Ice Shelf [in Antarctica] collapsed, some of the liberated inland glaciers increased their speed five fold.