The Getz Ice Shelf extends several miles into the ocean along the western Antarctic coast. The vertical face of the ice shelf is almost 200 feet high and is estimated to extend another 1,000 feet below the ocean surface. This photo was taken from a NASA DC-8 by Ted Scambos, Lead Scientist at the National Snow and Ice Data Center. Note: Thanks to a spring-break getaway, I'm just now catching up to this new research showing that warming ocean waters are threatening the stability of giant, floating shelves of ice fringing Antarctica. The post that follows offers a summary of the new findings, followed by a Q&A with the study's main author. By carving giant channels into the undersides of Antarctica's ice shelves, warming sea water is leaving some of them more vulnerable to disintegration — and raising new concerns about sea level rise. "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," says lead researcher, Karen Alley, a graduate research assistant at the National Snow and Ice Data Center, and a Ph.D. student at the University of Colorado in Boulder. (See note at the end of this post about my own connection to the University of Colorado.) These shelves form over thousands of years as ice flows off the mighty ice sheets of Antarctica and into the ocean through outlet glaciers. They can extend over the water for many miles, with bergs calving from their faces. They are, in essence, floating extensions of the grounded ice on the continent.
The cross-section above shows the transition from the grounded ice of an Antarctic ice sheet to a floating ice shelf. New research shows that warming Circumpolar Deep Water is carving channels into the undersides of Antarctic ice sheets, potentially weakening them and making them more vulnerable to disintegration. (Source: Bethan Davies, Antarcticglaciers.org. CC BY-NC-SA 3.0) The ice shelves also act like dams that impound the glaciers behind them, slowing their movement to the sea. Previous research has shown that Antarctic ice shelves are thinning faster than previously thought. This is of concern because as they erode, glaciers can flow more quickly, releasing more ice into the sea and thereby raising sea level. By weakening ice shelves from below, basal channels can only make the situation worse.
