Warm water chisels at ice shelf

A new scientific study published this week has found that warm ocean water is carving an enormous channel into the underside of one of the key floating ice shelves of West Antarctica, the most vulnerable sector of the enormous ice continent.

The Dotson ice shelf, which holds back two separate large glaciers, is about 1,350 square miles in area and 1,000- to 1,600-feet thick. But on its western side, it is now only about half that thickness, said Noel Gourmelen, a researcher at the University of Edinburgh in Scotland and the lead author of the research, which was just published in Geophysical Research Letters.

The reason is the same one that is believed to be shrinking glaciers and pouring ice into the ocean across West Antarctica — warm ocean water located offshore is now reaching the ice from below.

In Dotson’s case, it appears the water is first flowing into the deep cavity beneath the shelf far below it, but then being turned by the Earth’s rotation and streaming upward toward the floating ice as it mixes with buoyant meltwater. The result is that the warm water melts one part of the shelf in particular, creating the channel.

“We think that this channel is actually being carved for the last 25 years,” said Gourmelen, whose research team detected the channel using satellite observations. “It’s been thinning and melting at the base for at least 25 years, and that’s where we are now.”

The work was conducted by researchers at the University of Edinburgh along with colleagues at other institutions in France, Norway, the United Kingdom and the Netherlands.

The newly discovered channel is three miles wide and 37 miles long, and the scalloped region at the base of the floating ice shelf is mirrored by a long depression on its surface.

Dotson ice shelf as a whole has been thinning at an average rate of more than 8 feet per year since 1994, even as the speed of ice flowing outward through the shelf has increased by 180 percent. But the thinning in the channel has been far greater. The research calculates that 45 feet of ice thickness is being subtracted annually from the channel.

The new study calculates that as a result of this highly uneven melting, the Dotson ice shelf could be melted all the way through in 40 years, rather than 170 years, which would be the time it would take if the melt were occurring evenly. And it speculates that as the thinning continues, something dramatic, such as a breakup, could occur.