Melting faster in Antarctica

Western Antarctica has warmed unexpectedly fast over the last five decades, weather records confirm, adding to sea-level rise concerns in a warming world.

Temperatures in West Antarctica have increased at a rate nearly twice as large as the global average, a 4.3-degree Fahrenheit increase since 1958, conclude meteorologists in the journal Nature Geoscience.

The finding adds Western Antarctica to the list of hot spots most affected by global warming, the century-long increase in global average temperatures largely driven by greenhouse gas emissions from burning oil, gas and coal.

“The magnitude of the increase is substantial,” says polar meteorologist David Bromwich of Ohio State University, who led the study. “One of the most surprising aspects of this warming (increase) is how much is going on in the summer. That’s the time we would get any melting.” Bromwich had expected increases in rates of warming to be fairly uniform across the seasons, instead.

Antarctica’s Byrd Station temperature records reconstructed by the researchers find that year-by-year temperature increases accelerated there mostly in the 1980s. While melting of the West Antarctic Ice Sheet now contributes only a few millimeters of sea level rise per decade (comparable to Greenland), the collapse of the 10 million-square-mile Western Antarctic Ice Sheet underneath the station would trigger a 10-foot rise in sea level over a few centuries. The ice sheet rests frozen in a basin at sea level, and the fear is that it could slide into ocean waters if melting occurs at its base, raising water levels like an ice cube dropped into a glass.

“The rapid warming in West Antarctica is not a cause of ice sheet melting – but it is a symptom” of warmer ocean waters reaching Antarctica that actually do much of the melting, says climate scientist Eric Steig of the University of Washington in Seattle. Publication of the new temperature record study, “marks a definitive end to a significant controversy,” Steig says, started when his own team first published snow records in 2009 that surprised climate scientists by finding larger-than-expected temperature increases in Western Antarctica.

“I think this is news only in fitting into a pattern of studies showing warming in this (Western Antarctic) region,” says polar expert Ted Scambos of the National Snow and Ice Data Center at the University of Colorado, Boulder. “Temperatures are still largely below freezing in Western Antarctica, unlike Greenland, even with the warming seen in the study.”

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