Antarctic Sea Ice Reaches Record Highs Due to Increasing Polar Winds

First Posted: Sep 18, 2013 07:36 AM EDT

While temperatures have increased across the planet, something a bit strange is happening in the Antarctic--sea ice is increasing. In fact, there's more sea ice there now than in the 1970s and there may just be a record high this year in terms of ice coverage. Now, scientists may have an explanation behind this apparently growing sea ice: polar winds.

"The overwhelming evidence is that the Southern Ocean is warming," said Jinlun Zhang, one of the researchers, in a news release. "Why would sea ice be increasing? Although the rate of increase is small, it is a puzzle to scientists."

In order to find out what might be causing Antarctic sea ice to increase, the researchers created a computer model. The computer simulation included detailed interactions between the wind and sea. They found that thick ice, which is more than six feet deep, increased by about 1 percent per year from 1979 to 2010. The amount of thin ice, in contrast, stayed fairly constant.

"You've got more thick ice, more ridged ice and at the same time you will get more ice extent because the ice just survives longer," said Zhang.

How is this possible? It turns out that the polar vortex that swirls around the South Pole isn't just stronger than it was when satellite records began in the 1970s. This vortex also has more convergence, which means that it shoves the sea ice together to cause ridging. Stronger winds also drive ice faster, which leads to more deformation and ridging and, in the end, creates thicker ice.

"People have been talking about the possible link between winds and Antarctic sea ice expansion before, but I think this is the first study that confirms this link through a model experiment," said Axel Schweiger, polar scientists at the UW Applied Physics Lab, in a news release. "This is another process by which dynamic changes in the atmosphere can make changes in sea ice that are not necessarily expected."

Currently, researchers aren't quite sure why these southern winds have been getting stronger. It could be related to global warming or to the ozone depletion in the Southern Hemisphere, or could just be due to natural cycles.

That said, this trend is likely to reverse if temperatures continue to increase. Currently, scientists are working on improving models to better reproduce the increase in sea ice and predict what the future might bring.

"If the warming continues, at some point the trend will reverse," said Zhang.

The findings are published in the Journal of Climate.

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