Sun Dec 23, 2012, 01:26 PM
muriel_volestrangler (77,288 posts)
West Antarctica Warming More Than Expected
Last edited Sun Dec 23, 2012, 02:48 PM - Edit history (1)
In a discovery that raises further concerns about the future contribution of Antarctica to sea level rise, a new study finds that the western part of the continentís ice sheet is experiencing nearly twice as much warming as previously thought.
The temperature record from Byrd Station, a scientific outpost in the center of the West Antarctic Ice Sheet (WAIS), 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 will be published Sunday 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 NCARís 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,Ē says NCAR scientist Andrew Monaghan, a co-author. ďA 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.Ē
If it sounds like I donít think Bromwich et al.ís results are anything new, let me correct that impression. The contribution of this new paper is huge. Bromwich et al. rely almost entirely on local data to produce the best-possible record of temperature from one location ó Byrd Station in central West Antarctica. In contrast, our work relied heavily on interpolation of data from weather stations some distance from West Antarctica. Why didnít we use the same data Bromwich et al. did? Well, we did, but the problem is that the Byrd Station record is actually several different records, taken at different times using different instruments. We felt that we could not splice these records together into one continous record, because instrument inter-calibration issues could easiily create spurious trends.
One of the chief contributions of the Bromwich team is that they carefully checked the calibration on the various temperature sensors and dataloggers that are used in the Byrd automatic weather station. It turns out that there were significant calibration issues and that correcting for them makes the temperature higher in the 1990s but somewhat lower in the 2000s (though still higher than in the 1960 Ė 1980s). That is a compelling finding, because it puts the weather station data in better agreement with the climate forecast reanalysis data explaining the cause of the winter warming trends (as described e.g. in Ding et al., 2011; 2012).
Another new aspect of the Bromwich et al. paper is that it shows that there is significant warming even in summer time in West Antarctica. This could arguably bode ill for the West Antarctic Ice Sheet, since if current trends continue it will mean more melting on the ice shelves there ó ultimately leading to their collapse, as has already happened on the Antarctic Peninsula.
As Anais Orsi and I discuss in a News & Views article ó not yet online, but evidently to be in the Februrary print issue of Nature Geoscience ó Bromwich et al.ís results are objectively the best record available of the last five decades of temperature change in West Antarctica. Note that the while the borehole data are the most important independent validation, they provide only a smoothed look at past temperatures; they do not resolve interannual or decadal variability. Bromwich et al.ís updated record for Byrd Station should now be routinely incorporated into global temperature compilations such as those done by GISS and CRU. Doing so will, I think, change the picture of climate change in the Southern Hemisphere, and not insignificantly.
Article (abstract for free, body behind paywall):
Central West Antarctica among most rapidly warming regions on Earth
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