Climate change

Greenland melting faster

Print edition : February 15, 2019

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A new study led by Michael Bevis of the Ohio State University, published in the latest issue of the Proceedings of the National Academy of Sciences (PNAS), has found that the Greenland ice sheet is melting faster than scientists previously thought. The cause is continued and accelerating global warming. This rapid melt is likely to lead to faster sea-level rise.

The scientists have found that the source of this increased melt is the previously unsuspected region of the icy mass, the south-west Greenland. The focus of research on the melting of Greenland ice until now had been its south-east and north-west regions, where large glaciers discharge iceberg-sized chunks of ice into the Atlantic Ocean, which eventually melt.

But this new study has found that the largest sustained ice loss from early 2003 to mid 2013 came from Greenland’s south-west region, where there are no large glaciers, implying thereby that the changes were driven largely by changes in surface mass balance rather than changing rates of glacial discharge into the ocean.

“Whatever this was, it couldn’t be explained by glaciers, because there aren’t many there,” said Bevis. “It had to be the surface mass—the ice was melting inland from the coastline. Increasingly, large amounts of ice mass are going to leave as meltwater, as rivers that flow into the sea.”

This means that in south-west Greenland, growing rivers of water are streaming into the ocean during summer, and the region, which previously was not considered a serious threat, will likely become a major future contributor to sea-level rise.

This could have serious implications for coastal cities of the United States, including New York and Miami, as well as island nations that are particularly vulnerable to rising sea levels. “The only thing we can do is adapt and mitigate further global warming—it’s too late for there to be no effect. We are watching the ice sheet hit a tipping point,” Bevis warned. “Once you hit that tipping point, the only question is: How severe does it get?”

Climate scientists have been monitoring the Greenland ice sheet as a whole since 2002, when the National Aeronautics and Space Administration (NASA) and Germany joined forces to launch the twin satellites GRACE (Gravity Recovery and Climate Experiment), which measure ice loss across Greenland.

Data from GRACE showed that between 2002 and 2016 Greenland lost approximately 280 gigaton of ice a year, equivalent to 0.76 mm of sea-level rise each year. But the rate of loss was far from steady.

Bevis’ team used data from GRACE and from GPS stations scattered around Greenland’s coast to identify changes in ice mass. The patterns they found show an alarming trend. By 2012, the ice loss was nearly four times the rate in 2003, and it came from the south-west part of Greenland.

According to the scientists, a natural weather phenomenon called the North Atlantic Oscillation (NAO), which brings warmer air to West Greenland,and clearer skies and more solar radiation combined with the anthropogenic climate change were resulting in unprecedented levels of melting and runoff.

The results suggest that south-west Greenland could become a major contributor to sea-level rise under continued climate warming.

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