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May 2, 2008
Arctic Ocean ice floes.
High Resolution (Credit: NOAA)
While the Arctic and the Antarctic experience similar greenhouse gas levels and solar radiation, each region responds in a dramatically different way, especially in temperature and loss of sea ice, says an international team of scientists that includes a NOAA oceanographer. While the Arctic is warming, most of Antarctica is not, largely because of the ozone hole, but projections indicate that is likely to change.
“While some people would say this is a paradox, these different responses are mostly consistent with what we know about how the climate system works,” said James Overland, lead author and an oceanographer at NOAA’s Pacific Marine Environmental Laboratory in Seattle.
The findings, based on an October 2007 polar climate workshop, will be published in the May 6 issue of EOS, a publication of the American Geophysical Union. Co-authors are John Turner and Gareth Marshall of the British Antarctic Survey, Jennifer Francis of Rutgers University, Nathan Gillett of the University of East Anglia, and Michael Tjernstrom of Stockholm University.
Thirty scientists attended the Seattle workshop that looked at the Polar Regions from 1987 to 2007. The scientists concluded, based on new research since the 2007 Intergovernmental Panel on Climate Change Report, that a combination of factors is responsible for the recent dramatic sea ice loss in the Arctic as well as masking some of the effects in the Antarctic.
“In the Arctic, there is a combination of factors, such as warming of the air because of more greenhouse gases, an unusual wind pattern, and warming of the ocean water in regions with reduced sea ice,” said Overland.
Gillett, a climate dynamics scientist, said, “In the Antarctic, the changes in winds and temperatures are consistent with how we would expect them to respond to increased greenhouse gases and depletion of stratospheric ozone.”
The depletion of ozone has strengthened the atmospheric circulation, called the Southern Annual Mode, or SAM. As the ozone hole recovers, the winds that currently whiz around Antarctica and block air masses from crossing into the continent’s interior would weaken, and Antarctica would no longer be so isolated from global warming patterns.
“Additional warming of the ocean and an overall thinning of the sea ice makes it difficult for the Arctic to now return to earlier conditions,” says Overland.