The Big Arctic

By Kathy A SvitilNov 1, 2000 6:00 AM


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This summer the Russian icebreaker Yamal braved the frozen wasteland of the north pole— only to find, in place of the expected cap of 10-foot-thick ice, a broad swath of open sea. Was this a portent of global warming, coastal flooding, and ecological devastation, as many news reports maintained?

Impossible to say, until now. Using a Canadian satellite called RADARSAT, research scientist Ronald Kwok at NASA's Jet Propulsion Laboratory is creating comprehensive maps of the Arctic that will reveal whether things are really heating up. "For the first time, we can track all the cracks in the Arctic's ice cover. We can watch them form and then freeze over with thin ice, which will help us understand the Arctic Ocean as part of the global climate system," Kwok says. The satellite's synthetic-aperture radar can peer through persistent polar clouds and reveal features as small as a few hundred feet across, a resolution 100 times better than previously available.

The initial word from RADARSAT is reassuring. After sifting through one full season's worth of images, Kwok and his colleagues have found that huge rifts in the sea ice, which can measure a few miles wide and more than 1,000 miles long, are quite common. "Seeing open water at the north pole is not a remarkable thing. We see these cracks open and close all the time, and in the summer there are a lot of them," he says. So ice-free water is not, by itself, a reason to panic.

But there are other warning signs. Naval submarine data, for instance, hint that the thickness of sea ice over the Arctic Ocean has declined sharply in the past 40 years. RADARSAT could quantify the warming by monitoring the size and number of sea-ice cracks. Kwok is working on that, but it will take time. "Right now, we have a very short record of climate data in the Arctic, so it will be at least five to 10 years before we could have confirming evidence for warming," Kwok says.

RADARSAT snapshots of winter sea ice atop the Beaufort Sea (above) show tremendous changes over just nine days. Thick ice (light) rifts apart, exposing warmer water that quickly freezes in the cold air (dark). The ice cover both influences and responds to the Arctic climate.Photo by CSA/ Processed at the Alaskan SAR Facility

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