Harsher Winters Related to Arctic Sea Ice Loss

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PRI Living on Earth
Air Date: Week of October 31, 2014

A new study published in Nature Geoscience found that the likelihood of unusually cold winters in parts of Eurasia doubles as the Arctic warms and sea ice declines. Host Steve Curwood discusses the findings with Rutgers University climate researcher Jennifer Francis, who also explains how rising temperatures in the far north are changing world weather.

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2014 is on track to be the warmest year on record, but if you think the trend might bring a mild winter, you could be out of luck. A new study from Tokyo indicates that the increased melting of Arctic sea ice is linked to colder winters, at least in parts of Europe, Asia, and North America.

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there's only about half as much sea ice coverage in the Arctic now as there was only 30 years ago. It's just been disappearing at an amazing rate. One of those regions where the ice is disappearing the fastest is just north of Scandinavia and western Russia, an area called the Barents-Kara Sea area. What we're learning about this area is that it's very important for the atmosphere.

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When we lose that ice there, the dark ocean underneath during the summertime absorbs a lot of extra energy from the sun, and so that water warms up a lot more than it used to. When fall comes along and the cold air starts to move in again, all that energy that was absorbed through the summer in that region then gets re-emitted back to the atmosphere and that causes the air above this region to warm up a lot. This has the effect of actually bulging the jetstream northward. The jetstream is this fast-moving river of air high over our heads that generates the weather that we experience down here on the surface, and when it is forced to bulge northward like that it compensates by bulging southward just downstream, which would be to the east. When that happens, it allows the cold air from the Arctic to plunge farther south, and so what we're seeing is; during summers when there's less ice than normal in this Barents-Kara Sea area we're finding the jet stream taking this wavier path with the bulge up north of Scandinavia and then a big dip south over Asia allowing that cold air to plunge southward and creating those colder winters.

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Yes, natural variability is alive and well.

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these cold...extra cold winters in Asia were twice as likely to occur when they put reduced sea ice in this Barents- Kara Sea area as compared to when there was lots of ice in that area. [So the computer models match what has actually been happening]

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What happened this past winter that kind of got misnamed the polar vortex, really was that we had one of these big southward dips in the jetstream in combination with the big northward swing over California and the Eastern Pacific. Because we had this big southward dip in the jet stream, a very wavy pattern, it allowed the Arctic air to plunge southward over much of the eastern half of the country. And because the waves were so big in the jet stream that made that pattern very persistent so it hung around for a long time.

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Over the last few decades, however, that ice has been thinning and it's been thinning because of increasing greenhouse gases, so that when it does melt back in the summer as it normally does, a lot more of that sun's energy gets absorbed into the Arctic Ocean, which then contributes to even more melting, so we've gotten into this vicious cycle that means that the more ice we lose the more ice we melt and the warmer it gets in the Arctic, and so we're in the situation now where it really can't recover.

CURWOOD: What does that mean?

FRANCIS: Well it means that we are in for a lot more evidence of climate change. We're already seeing an increase in heat waves. We're seeing an increase in the occurrence of heavy downpours and heavy precipitation events. These are completely expected as a result of the effects of global warming because a warmer atmosphere can hold more water vapor and more moisture, and so when it does rain, it rains harder. We're seeing an increase in drought in certain areas, so we are changing the climate system in fundamental ways. People just need to start realizing that and realizing that we're not going to turn this thing around unless we can really come to grips with figuring out ways to put less greenhouse gases into the atmosphere.

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