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New analysis find West Antarctic warming more than expected
24 December 2012
A new study using a computer model of the atmosphere and a numerical analysis method to fill in gaps in collected data from the Byrd Station outpost finds that the central region of the West Antarctic Ice Sheet (WAIS) is experiencing twice as much warming as previously thought.
Due to its location some 700 miles from the South Pole and near the center of the WAIS, conditions at Byrd Station are an important indicator of climate change throughout the region. In the past, researchers haven’t been able to make much use of the Byrd Station measurements because of incomplete temperature observations. Since its establishment in 1957, the station has not been occupied continuously. A year-round automated station was installed in 1980, but it has experienced frequent power outages, especially during the long polar night when its solar panels can’t recharge.
The new study finds that the temperature record from Byrd Station demonstrates a marked increase of 4.3 degrees Fahrenheit (2.4 degrees Celsius) in average annual temperature since 1958. The rate of increase is three times faster than the average temperature rise around the globe for the same period.
The study is published in the journal Nature Geoscience. It was conducted by scientists at Ohio State University (OSU), the National Center for Atmospheric Research (NCAR), and the University of Wisconsin-Madison, with funding coming from the National Science Foundation, which is NCAR’s sponsor.
Our results indicate that temperature increases during the past half century have been almost twice what we previously thought, placing West Antarctica among the fastest warming regions on Earth. A growing body of research shows that the West Antarctic Ice Sheet is changing at an alarming rate, with pressure coming from both a warming ocean and a warming atmosphere.—NCAR scientist Andrew Monaghan, a co-author
This study reveals warming trends during the summer months of the Southern Hemisphere (December through February), notes co-author David Bromwich, professor of geography at Ohio State University and senior research scientist at the Byrd Polar Research Center.
Our record suggests that continued summer warming in West Antarctica could upset the surface mass balance of the ice sheet, so that the region could make an even bigger contribution to sea level rise than it already does. Even without generating significant mass loss directly, surface melting on the WAIS could contribute to sea level indirectly by weakening the West Antarctic ice shelves that restrain the region’s natural ice flow into the ocean.—David Bromwich
Researchers consider the WAIS especially sensitive to climate change because the base of the ice sheet rests below sea level, making it vulnerable to direct contact with warm ocean water. Its melting currently contributes 0.3 millimeters to sea level rise each year. This is second only to Greenland, whose contribution to sea level rise has been estimated as high as 0.7 mm per year.
In addition to offering a more complete picture of warming in West Antarctica, the new study shows for the first time that significant melt is occurring during summer. Monaghan says the summertime warmth is particularly troubling because that is the season in which enhanced surface melting could most affect the WAIS and potentially weaken the ice shelves that buttress it.
We’ve already seen enhanced surface melting contribute to the breakup of the Antarctic’s Larsen B Ice Shelf, where glaciers at the edge discharged massive sections of ice into the ocean that contributed to sea level rise. The stakes would be much higher if a similar event occurred to an ice shelf restraining one of the enormous WAIS glaciers.—Andrew Monaghan
West Antarctica is one of the most rapidly changing regions on Earth, but it is also one of the least known. Our study underscores the need for a reliable network of meteorological observations throughout West Antarctica, so that we can know what is happening—and why—with more certainty.—David Bromwich
David H. Bromwich, Julien P. Nicolas, Andrew J. Monaghan, Matthew A. Lazzara, Linda M. Keller, George A. Weidner & Aaron B. Wilson (2012) Central West Antarctica among the most rapidly warming regions on Earth. Nature Geoscience doi: 10.1038/ngeo1671
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