Warming ocean water undercuts Antarctic ice shelves

http://www.eurekalert.org/pub_releases/2016-03/uoca-wow031416.php

Public Release: 14-Mar-2016
Warming ocean water undercuts Antarctic ice shelves
University of Colorado at Boulder

"Upside-down rivers" of warm ocean water threaten the stability of floating ice shelves in Antarctica, according to a new study led by researchers at the University of Colorado Boulder's National Snow and Ice Data Center published today in Nature Geoscience. The study highlights how parts of Antarctica's ice sheet may be weakening due to contact with warm ocean water.

"We found that warm ocean water is carving these 'upside-down rivers,' or basal channels, into the undersides of ice shelves all around the Antarctic continent. In at least some cases these channels weaken the ice shelves, making them more vulnerable to disintegration," said Karen Alley, a Ph.D. student in CU-Boulder's Department of Geological Sciences and lead author of an analysis published today in Nature Geoscience.

Ice shelves are thick floating plates of ice that have flowed off the Antarctic continent and spread out onto the ocean. As ice shelves flow out to sea, they push against islands, peninsulas, and bedrock bumps known as "pinning points." Contact with these features slows the flow of grounded ice off the continent. While ice shelves take thousands of years to grow, previous work has shown that they can disintegrate in a matter of weeks. If more ice shelves disintegrate in the future, loss of contact with pinning points will allow ice to flow more rapidly into the ocean, increasing the rate of sea level rise.

"Ice shelves are really vulnerable parts of the ice sheet, because climate change hits them from above and below," said NSIDC scientist and study co-author Ted Scambos. "They are really important in braking the ice flow to the ocean."

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