Climate: Ice-free Arctic ahead?

A warming Arctic is changing the configuration of the jet stream, which affects mid-latitude weather. GRAPHIC COURTESY NOAA.

Researchers cautious about predicting the demise of Arctic ice

By Bob Berwyn

SUMMIT COUNTY — Despite a steady trend of melting Arctic sea ice, experts with the National Oceanic and Atmospheric Administration aren’t yet willing to make any predictions as to when the region will be completely ice-free during the summers.

The National Snow and Ice Data Center earlier this week said that the melt bottomed out in mid-September at new record low extent, but lingering thick, multi-year ice along the north coast of Greenland may persist for decades to come, preventing a total melt-out, said  NSIDC ice researcher Walt Meier, speaking during a Sept. 20 teleconference.

That may lead to a plateau at some during what’s been somewhat sensationally described as the Arctic ice death spiral, Meier said, adding that conditions are so variable from year to year that it’s hard to predict the timing.

Other climate researchers have speculated that, based on current trends, Arctic summer sea ice is likely to disappear within a few decades.

Meier said that, in addition to the low sea ice extent, the other big story is the overall loss of ice mass, with the majority of Arctic sea ice now just one or two years old and only a few feet thick.

In the past, much of the ice was older, and up to 10 or 15-feet thick, he said. The trend toward thinner ice has obvious implications — it’s not likely to last as long when temperatures start to warm up in the spring and is huge factor in the total volume of Arctic sea ice.

Meier also addressed the trend of increasing sea ice around Antarctica, which recently hit a high mark for this time of year.

Meier said the processes driving sea ice formation and melt are quite different. Around Antarctica, the extent of the ice is driven primarily by winds; in the Arctic, the ice is more influenced by air temperatures, he explained, adding that there is very little thick multi-year ice around Antarctica.

Most climate researchers expect that, as temperatures increase around Antarctica, the sea ice there will also melt away. Some current research shows that increasing sea temperatures in the region are already melting coastal ice from underneath, leading to collapsing shelves and potentially, accelerated loss of ice from the continent.

But this year’s record low extent may play out with some impacts on mid-latitude weather, especially in the fall and early winter, when the large expanse of open, dark-colored (relative to ice) water releases heat back into the atmosphere.

“You don’t want to overplay the impacts on precipitation,” Meier cautioned, then went on to explain some of the potential impacts, including more precipitation in coastal areas surrounding the Arctic due to a super-sized version of lake-effect snows familiar to residents of the northeast.

The increased energy being released from the water could also lead to stronger storms, resulting in bigger waves and more erosion, which is already a significant issue in some coastal areas of Alaska, he said.

Other research has suggested that generally warmer temperatures in the Arctic lead to a smaller pressure gradient between the high- and mid-latitudes, which may slow the jet stream and alter weather patterns. Studies by Jennifer Francis, with the Rutgers University Institute of Marine and Coastal Sciences show a direct link between changes over the Arctic and mid-latitude weather patterns driven by the jet stream.

“I expect to see two main effects,” Francis said during a weather conference in Breckenridge, Colorado last winter, explaining that north-to-south temperature gradient drive the jet stream, and in the past several  decades, there’s been a 20 percent drop in the zonal west-to-east wind speeds.

As that zonal flow slows down, it leads to those bigger kinks in the jet stream. That amplification is associated with persistent weather patterns that lead to “extremes” like drought, flooding and heat waves.

“Look at 20 coldest days in Tampa — you can see the patterns — A big ridge in the West, a big trough in East … It’s the same if you look at the wettest days in Chicago,” she said, explaining that a persistent trough of low pressure over the high plains brings moist air into the upper Midwest.

Those slow-moving, persistent waves of weather energy may have played a role in the across the West last winter, as well as some of the extreme winter weather that hit Europe.


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