While it is true that the overall sea ice extent surrounding Antarctica has been trending slightly upward since 1979 it is not all that unexpected despite global warming.
I have been getting a number of comments within this blog and even in the office asking why there was a recent daily record high sea ice area in the Antarctic despite the warming climate.
Image below courtesy of the Polar Research Group from the University of Illinois-Urbana-Champaign.
August trend of sea ice extent in the northern Hemisphere summer.
August trend of sea ice extent in the southern hemisphere winter.
Image courtesy of the NSIDC.
According to the experts at the National Snow and Ice Data Center...........
1. The main reason that Antarctica and the Arctic are reacting differently to climate change is partly due to significant geographical differences. Antarctica is a continent surrounded by water, while the Arctic is basically ocean surrounded by land.
2. Wind and ocean currents surrounding Antarctica isolate the continent from global weather patterns, thus keeping it cold. The Arctic Ocean is much more linked with the climate systems around it, making it much more sensitive to climate change.
3. Almost all of the sea ice that forms around the Antarctic in the winter melts out each year as the sea ice is free to float northward into warmer waters.
Nice explanation from the NSIDC........
Is wintertime Antarctic sea ice increasing or decreasing?
Wintertime Antarctic sea ice is increasing at a small rate and with substantial natural year-to-year variability. Specifically, the months of May, June, July, September and October show trends of increasing sea ice extent that are just slightly above the mean year-to-year variability. In more technical terms, the trends are statistically significant at the 95% level, although small.
Climate model projections of Antarctic sea ice extent are in reasonable agreement with the observations to date. The dominant change in the climate pattern of Antarctica has been a gradual increase in the westerly circumpolar winds. Models suggest that both the loss of ozone (the ozone hole that occurs in September/October every year) and increases in greenhouse gases lead to an increase in this climate pattern.
When winds push on sea ice, they tend to move it in the direction they are blowing, but the Coriolis effect adds an apparent push to the left. In the unconfined system of Antarctic sea ice, this pushes the ice northward away from the continent. By spreading sea ice westward and a little northward (and since we measure extent with a 15% cut-off) the gradual trend towards faster mean winds means a gradual trend toward spreading of the ice cover.
Even if wintertime Antarctic sea ice were to increase or decrease significantly in the future, it would not have a huge impact on the climate system. This is because during the Antarctic winter energy from the sun is at its weakest point; its ability or inability to reflect the sun's energy back into space has little affect on regulating the planet's temperature.
Also from the September 21st Christian Science Monitor article.......
"Antarctic sea ice hasn't seen these big reductions we've seen in the Arctic. This is not a surprise to us," said climate scientist Mark Serreze, director of the NSIDC. "Some of the skeptics say 'Well, everything is OK because the big changes in the Arctic are essentially balanced by what's happening in the Antarctic.' This is simply not true."
"Another reason why the sea-ice extent in the Antarctic is remaining fairly high is, interestingly, the ozone hole," Serreze told Life's Little Mysteries. This hole was carved out over time by chlorofluorocarbons, toxic chemicals formerly that were used in air conditioners and solvents before being banned. "The ozone hole affects the circulation of the atmosphere down there. Because of the ozone hole, the stratosphere above Antarctica is quite cold. Ozone in the stratosphere absorbs UV light, and less absorption [by] ozone makes the stratosphere really cold. This cold air propagates down to the surface by influencing the atmospheric circulation in the Antarctic, and that keeps the sea ice extensive."
But these effects are very small, and Antarctic sea-ice levels have increased only marginally. In the coming decades, climate models suggest rising global temperatures will overwhelm the other influences and cause Antarctic sea ice to scale back, too.
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