Thursday, May 10, 2012

New weakness in Antarctic ice sheet discovered

Stephanie Pappas in LiveScience: A new sector of the Antarctic Ice Sheet is at risk of melting rapidly within the next century, new research finds. The study raises alarm about an area thought relatively safe from the direct influence of climate change. The Filchner-Ronne Ice Shelf in the Weddell Sea is somewhat sheltered from the open sea, but the new research suggests that warm ocean currents could soon invade its underbelly, melting the shelf from below.

"The Weddell Sea was not really on the screen because we all thought that, unlike the Amundsen Sea, its warm waters would not be able to reach the ice shelves," said study researcher Hartmut Hellmer. Melting is accelerating at the Amundsen embayment across the Antarctic Peninsula from the Weddell Sea. The results of their new study, published Wednesday (May 9) in the journal Nature, surprised Hellmer, an oceanographer at the Alfred Wegener Institute in Germany, and his colleagues. "We found a mechanism which drives warm water towards the coast with an enormous impact on the Filchner-Ronne Ice Shelf in the coming decades," Hellmer said in a statement.

Hellmer and his colleagues used multiple models to determine how the ocean will respond to the atmosphere in the upcoming 200 years. They found that rising air temperatures above the southeastern Weddell Sea will thin the ice there, and warm ocean water will increasingly encroach beneath the Filchner-Ronne Ice Shelf.

...By the end of the 21st century, the researchers found, the melting of the Filchner-Ronne Ice Shelf will go from today's average rate of 0.7 feet (0.2 meters) of ice loss per year to 13 feet (4 m) per year. In some spots, as much as 164 feet (50 m) of ice will be lost each year. At a rate of 4 meters of ice loss per year, the ice sheet will shed 1,600 billion metric tons of ice annually....

Within a 24-hour space, an area of sea ice larger than the state of Rhode Island broke away from the Ronne-Filchner Ice Shelf and shattered into many smaller pieces. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua and Terra satellites captured this event in January, 2010.

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