November 14, 2012
NASA Study Looks At Increase In Antarctic Sea Ice
Alan McStravick for redOrbit.com — Your Universe Online
A new study by NASA and the British Antarctic Survey tries to explain the increase of ice cover in the Antarctic that is seemingly contrary to the effects of climate change that have been witnessed over the previous two decades.In their report, they purport they have the first direct evidence that this increase in sea ice cover is due to changing winds that have had an impact on the changes to Antarctic sea ice drift. The scientists involved believe their results will actually help explain why, unlike the sea ice recession reported in the Arctic, Antarctic sea ice cover has increased under the effects of climate change.
The team is led by research scientists Ron Kwok of NASA´s Jet Propulsion Laboratory (JPL) out of Pasadena, California, and Paul Holland of the Natural Environment Research Council´s British Antarctic Survey (BAS) in Cambridge, United Kingdom. Their study is based on JPL maps that used more than 5 million individual daily ice-motion measurements. The data for these maps were captured over a period of 19 years by four U.S. Defense Meteorological satellites. The scientists say the maps show, for the first time, long-term changes in sea ice drift around Antarctica.
"Until now, these changes in ice drift were only speculated upon, using computer models of Antarctic winds," said Holland, lead author of the study published this week in the journal Nature Geosciences. "This study of direct satellite observations shows the complexity of climate change. The total Antarctic sea ice cover is increasing slowly, but individual regions are actually experiencing much larger gains and losses that are almost offsetting each other overall.
"We now know that these regional changes are caused by changes in the winds, which, in turn, affect the ice cover through changes in both ice drift and air temperature," he continued. "The changes in ice drift also suggest large changes in the ocean surrounding Antarctica, which is very sensitive to the cold and salty water produced by sea ice growth."
According to Holland, strong northward winds are responsible for the sea ice around Antarctica being blown away from the continent. “Since 1992, this ice drift has changed,” he says. “In some areas, the export of ice away from Antarctica has doubled, while in others it has decreased significantly.”
Playing an important role in the Earth´s environment, sea ice is responsible for reflecting heat from the sun and also for providing a habitat for marine life underneath it. During their respective summer months, both poles experience sea ice cover at its minimum. But during the winter freeze in Antarctica, the sea ice cover typically expands to an area that is twice the size of Europe. This sea ice can range in thickness anywhere from 3 feet to several meters. The ice cover actually helps to insulate the warm ocean waters from the exceptionally frigid atmosphere above.
Kwok and Holland´s research also explains why the observed changes in sea ice cover are vastly different between the Arctic and Antarctic regions. While the Arctic has suffered severe ice loss in recent decades, the overall ice extent in the Antarctic has managed to increase, if even only slightly. The modest increase, though, is actually as a result of much larger regional increases and decreases. As stated above, the scientists have determined this is due to wind-driven changes in the polar environment. While increased northward winds have caused the Antarctic sea ice cover to expand ever outward, the Arctic Ocean is landlocked which prohibits a similarly styled expansion at this pole.
"The Antarctic sea ice cover interacts with the global climate system very differently than that of the Arctic, and these results highlight the sensitivity of the Antarctic ice coverage to changes in the strength of the winds around the continent," said Kwok.
The effects of climate change have had contrasting impacts across the Antarctic continent over the past few decades. The Antarctic Peninsula has seen temperature increases that mirror much of the Southern Hemisphere. By contrast, East Antarctica has shown little change and even small degrees of cooling around its coast. Kwok and Holland contend that their research helps to aid in an improved understanding of both present and future climate change.
Both Kwok and Holland feel it is especially noteworthy to point out that their study focuses on Antarctic sea ice which is frozen sea water. The Antarctic Ice Sheet, which is glacial ice, has been steadily losing volume over time.
The research was funded by NASA and the Natural Environment Research Council.