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[music]

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I'm Michael Starobin on the flight deck of NASA's

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airborne science laboratory -- it's a customized DC-8.

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We're in Punta Arenas, Chile on the trail ... of a mystery.

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Kurtz: Ah, the current trend in Antarctic

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sea ice is, it's been expanding. Starobin: We know this much already

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global climate is getting warmer. Huge quantities

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of ice are disappearing from both poles, and from glaciers around

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the world. So if things are heating up? Why is

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the quantity of ice increasing around the coast of Antarctica?

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Kurtz: So it actually is very counter-intuitive that Antarctic sea ice

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would be increasing when global temperatures are also increasing because you would

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expect it to melt, such as has been happening in the Arctic.

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Starobin: But it's not. Sea ice is increasing around the southernmost continent.

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And scientists are trying to understand why. They're closing in

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on suspect causes. Kurtz: The major component that

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looks like it's contributing to the expansion of sea ice has been the increase of winds

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from the Antarctic continent. Starobin: But why those winds are increasing

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is still a matter of some debate, including an unexpected suspect.

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Kurtz: One of the prevailing thoughts on why winds have

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strengthened from the Antarctic continent outward to the sea, is because of

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the ozone hole in the Antarctic. And

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climate models have been run showing that if you have

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an ozone hole, the winds are much stronger than if you don't

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have an ozone hole. Starobin: But there are other causes too. A warmer planet

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is likely to provoke higher rates of precipitation.

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Kurtz: The increase in snowfall in particular would happen

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and put fresh water into the ocean, at which point you have

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a fresh layer that sits on top of a saltier layer.

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Starobin: Freshwater freezes faster than saltwater. A warmer planet means more

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fresh water, which is why a warmer planet means more

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ice. Does the increase in sea ice around Antarctica

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offset the decrease in sea ice in the North?

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Kurtz: The decrease in Arctic sea ice has been about three times the increase in Antarctic sea ice.

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So the actual amount of sea ice lost on the planet has been going down

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substantially. It's a very unknown problem and

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requires a lot of basically observations from scientists.

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Starobin: Which is precisely why a team of specialized investigators

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are in the field with Operation IceBridge, making vital observations

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to better understand how Earth's climate is changing, and why.

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[music]

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