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Exploring global climate impact if Antarctica's ice sheets melt

UMass Amherst climate researchers address gap in Antarctic ice model

University of Massachusetts at Amherst

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IMAGE: Modern day ocean surface temperatures around Antarctic are simulated in this image by a high-resolution ocean model, with red areas warmer and blue areas colder. White around the Antarctic continent... view more

Credit: UMass Amherst/Anthony Coletti

AMHERST, Mass. - As the world anticipates a global climate change meeting next month in Paris, there is compelling historical evidence that the West Antarctic Ice Sheet is vulnerable to rapid retreat and collapse, says climate scientist Alan Condron at the University of Massachusetts Amherst, yet very few if any studies have explored what might happen to Earth's climate if Antarctica's ice sheets were to melt over the next few decades.

Now Condron has a three-year, $692,694 grant from the National Science Foundation to lead modeling studies of such a scenario. He explains, "A lot of the climate modeling work done up to now has focused on the Arctic, on investigating what might happen if you freshen the ocean in the North Atlantic, for example, if Greenland's ice sheets were to melt. But no one has been thinking much about what happens to climate if Antarctica's major ice sheets suddenly melt, say over the next 50 to 100 years. It's a huge gap in the research."

Antarctica's ice sheets hold perhaps eight times more fresh water than Greenland's ice cap, Condron adds. He and his UMass Amherst Climate Systems Research Center colleague Robert DeConto, with David Pollard at Pennsylvania State University, will team up on this grant to investigate what a huge freshwater influx might do to ocean currents and circulation around the Antarctic continent and also farther away in the North Atlantic.

"In fact we are very interested in knowing whether melting from Antarctica can cause the Gulf Stream in the North Atlantic to suddenly weaken and the climate of Europe and the United States to become much colder," he notes. "Such change in the near future poses a threat to modern climate and societies."

Globally, ocean currents play a key role in moving heat between the tropics and the poles, Condron points out. Specifically, the Antarctic circumpolar ocean current, one of the largest on the planet, is a continuous fast flow around the continent that forms a barrier, isolating Antarctic cold.

"We don't know what would happen if that current or other large ocean currents are disrupted or if the speed changes, but we do know ocean currents play a big role in keeping Antarctic cold locked up and in moving heat around the globe. If ocean currents are disrupted, it could affect weather patterns and might have a big impact in North America or Europe. Changes in rainfall and temperature could affect crops and forests tens of thousands of miles away from Antarctica," he adds.

"If something's going to happen to the Earth's climate because the Antarctic ice sheet is melting, we want to know about it." Condron and colleagues will use a high-resolution eddy-resolving ocean model known as MITgcm, with a new iceberg module and fully coupled global climate model, CCSM4, to simulate iceberg calving, drifting and melting and to project freshwater discharge.

Predictions vary wildly at present, Condron says, but there is clear evidence that Antarctic glaciers are now moving faster, ice sheets are thinning and instability cracks are more numerous. Right now there are not enough high-resolution simulation studies with the many thousands of data points needed to yield a realistic picture of what freshening the ocean around Antarctic might do to ocean currents in the North Atlantic.

Results of this work will help identify ice sheet areas vulnerable to collapse and ocean regions where significant freshening might have a considerable impact on climate. Findings will also guide researchers in deploying new observational monitors able to warn when ice and fresh water discharge start to approach levels capable of disrupting ocean circulation and global climate.

The project will support and train two graduate students. In addition, Condron, DeConto and Pollard plan to be involved with local schools by making presentations, mentoring science fair projects and helping to develop curriculum.

In Amherst, Condron and DeConto are developing a computer-based game, expected to be ready next spring, for elementary school children to help them learn about the importance of Polar Regions in global climate. The researchers plan to introduce the software to science teachers at a half-day workshop organized by the UMass STEM Education Institute.

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