The Hot Zone

Where ice meets sea

Posted by Alison Hawkes on July 7, 2010
Category : The Oceans

How fast can a glacier melt? Usually the answer is attributed to the amount of warming or CO2 level rise.

But researchers are also looking into the actual mechanics of glacier melt to get a handle on what’s causing ice to wear away. In a paper published recently in Nature Geoscience, Adrian Jenkins of the British Antarctic Survey and colleagues examined Pine Island Glacier, one of the two main contributors of ice loss in West Antarctica.

Pine Island Bay, 1984. Photo by Tom Kellogg onboard the U.S. Coast Guard icebreaker Glacier

Pine Island Bay, 1984. Photo by Tom Kellogg onboard the U.S. Coast Guard icebreaker Glacier

West Antarctic holds enough water to boost global sea levels by several meters because much of the ice shelf is on solid ground. Any loss directly adds water to the ocean. And it’s happening fast. About 10 percent of the observed rise in global sea level is from West Antarctica.

About twice the size of Scotland, Pine Island Glacier has accelerated thinning, the most deleterious section occurring along the coast. Researchers sent an autonomous underwater vehicle to roam 510 km under the ice shelf to map out the topography where the glacier meets the sea.

A heavily crevassed section of Pine Glacier Island. Photo courtesy of NASA.

A heavily crevassed section of Pine Glacier Island. Photo courtesy of NASA.

It found that warm, circulating water is chipping away at the ice sheet from a cavity below. The glacier used to extend all the way to the crest of a ridge, but its retreat of some 30 km since the 1970s has exposed the ice shelf to a underwater cavity that is slowly getting bigger and more pronounced. This further destabilizes the ice shelf.

The thinner the ice, the researchers write, the greater the effect. The topography of the land suggests that this retreat could go on for another 200 km until it reaches the next rise in the ridge.

They believe what’s happening at Pine Island Glacier could be similar to other locations around Antarctica, where ice meets sea.

-Alison Hawkes

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