Arctic sea ice melting faster than expected
If the pattern continues, warming effects could reach up to 900 miles inland, melting permafrost
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He and colleagues published an analysis last week showing that ice in the Beaufort Sea – which stretches from Barrow, Alaska, east to Canada’s islands in the high Arctic – underwent what he terms an extraordinary amount of melting from underneath due to warm water. Some of that water may have flowed into the Beaufort Sea from the Pacific or via the Atlantic, he acknowledges. But buoy measurements locally point to “enough solar heat to easily be responsible for this huge amount of bottom melting and still have heat left over.”Skip to next paragraph
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The seawater retained enough residual heat, in fact, to significantly slow the freeze-up of sea ice heading into last winter. The intensity of this classic “ice-albedo feedback” may be one reason why the Arctic is responding so much faster to global warming than many climate models had projected, he says. The results appeared in the June 3 issue of Geophysical Research Letters.
The question now: “We see this big drop; are we going to hit a plateau and bounce around for a while or are we in free-fall?” he asks.
It’s a question whose answer may have implications well below the Arctic Circle. High-latitude warming – when reinforced by a five- to 10-year period of sudden, deep sea-ice meltbacks – could be 3.5 times higher than climate models typically project, according to a study published this week and prompted by last year’s sea-ice meltdown. Moreover, the added warmth extends as far as 900 miles deep into the North American and Eurasian continents.
“That was one of the real interesting aspects of this study – just how broad the impact can be,” says David Lawrence, a scientist at the National Center for Atmospheric Research who led the group. The earlier these extended periods of low-ice summers appear during this century, the study shows, the sooner the most vulnerable forms of permafrost melt, and the more vulnerable colder forms of permafrost become to later climate warming. His group’s study appears in the June 13 issue of Geophysical Research Letters.
The long-term climate implications of melting permafrost are unclear. Much depends on what happens to the hydrology of the region, Dr. Lawrence says. Carbon dioxide or methane could be the predominant gas vented as permafrost melts, depending on how wet or dry the region becomes. And as woodier vegetation migrates north, soaking up some of that CO2 in the process, the region still could emit enough methane – a far more potent greenhouse gas than CO2 – to offset the CO2 plants take up.
“The Arctic is a real challenge; it’s a complicated place up there,” he says.