June 21, 2010
Shedding Light On Melting Pine Island Glacier
A robotic yellow submarine that has been launched deep beneath the Pine Island Glacier has helped to solve a mystery about one of Antarctica's fastest-melting glaciers, adding to unease about how climate change may lead to higher world sea levels, scientists reported on Sunday in the journal Nature Geoscience.
Scientists captured ocean and sea-floor measurements using the robotic submarine, called Autosub.The team found that the glacier was no longer resting on a sub-sea ridge that had slowed the glacier's slide until the early 1970s.
Antarctica is key to predicting the rise in sea levels due to global warming. Antarctica has enough ice to raise sea levels by 187 feet if it all ever melted. Even if a small fraction of the ice was to thaw out, it could flood coastal regions from Bangladesh to Florida.
The findings, which come from a 2009 mission, add to the concern that "this region is indeed the "Ëweak underbelly' of the West Antarctic Ice Sheet," co-author of the study Stan Jacobs at the Lamont-Doherty Earth Observatory said in a statement.
10 percent of a recently studied rise in sea levels is attributed to thawing ice from West Antarctica.
As Pine Island Glacier continues to thaw at a more rapid rate, especially in recent decades, more regions will be affected by the rising sea waters, according to the study led by the British Antarctic Survey.
Loss of contact with the sub-sea ridge means that ice is flowing faster and also thawing more as sea water flowed into an ever larger cavity that now extends nearly 20 miles beyond the ridge.
Satellite photographs taken in the early 70s showed a bump on the surface of the ice shelf, indicating the presence of a sub-sea ridge. The bump has now vanished and the Autosub found the ridge was now up to 300 feet or more below the ice shelf.
This study raises "new questions about whether the current loss of ice from Pine Island Glacier is caused by recent climate change or is a continuation of a longer-term process that began when the glacier disconnected from the ridge," Adrian Jenkins, lead author at BAS, told Reuters.
Pierre Dutrieux, also at BAS, said the ice may have started thinning because of some as yet-unknown mechanism linked to climate change, blamed mainly on mankind's use of fossil fuels.
A UN panel of climate experts projected in 2007 that world sea levels could rise as much as 24 inches by 2100, not including risks of faster melting in Antarctica and Greenland. A worst-case scenario could put the rise to as much 6.5 feet, said UN Secretary-General Ban Ki-Moon.
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