An Arctic hurricane?

This satellite image from November 8 shows the hurricane-like storm that hit Western Alaska earlier this month. Credit: NASA Earth Observatory image created by Jesse Allen, using data obtained from the Land Atmosphere Near real-time Capability for EOS (LANCE).

On November 8 and 9, a strong storm hit the Western Alaska coast, bringing blizzard conditions, storm surge of up to 10 feet and wind gusts as fast as 93 miles per hour. Along the Western Alaskan coastline, towns and villages prepared for the worst. “Up here, cities are much more sparse, but a storm like this still impacts the people that live there,” said Kathleen Cole, an ice forecaster at the National Weather Service. Damage reports after the storm indicated extensive flooding, wind damage to buildings, as well as power outages, which led to many evacuations to higher ground and to shelters with generator power. Some reports referred to the storm as a “blizzicane,” or an Arctic hurricane. What was unusual about this storm—and was there any connection to changes in the Arctic climate?

The November storm was a strong low-pressure system that brought heavy rain, snow, and wind up from the north Pacific into the Bering Sea, said James Nelson, of the National Weather Service in Anchorage, Alaska. Winds were comparable to a Category 1 hurricane, and storm surge equal to a Category 3 hurricane, Nelson said. But although the storm resembled a hurricane, it did not meet the criteria of an “Arctic Hurricane,” technically called a polar low, a storm type that forms and remains within the Arctic, and usually lasts less than a day.

This map shows the peak wind speeds recorded during the November 8th storm that hit Western Alaska. Credit: James Nelson, NOAA National Weather Service

Storms, climate, and sea ice

The storm was unusual because it occurred so early in the winter, before sea ice had formed into a thick covering that can dampen waves. Some media coverage of the storm suggested that less sea ice covering the ocean left the coastal areas more vulnerable to the storm than they would have been otherwise. But in the region where the storm hit, Cole said, sea ice extent was actually pretty close to average for that time of year.

So while sea ice continues to trend strongly downward on average, this did not play a role in the storm’s force. It was the timing of the storm that made it so destructive. “Storms this strong don’t typically happen this early in winter,” Nelson said. Such storms may form three or four times in a winter, but the Bering Sea coast has not seen one in November for almost 40 years. This system was one of the more powerful storms to affect western Alaska since 2004, though the storm in October of that year had a track that was farther west over Russia. The track of the 2011 storm was similar to a major storm in November 1974 which moved north over the central Bering Sea, across the Bering Strait to the Lisburne Peninsula.

While the damage from this particular storm was not intensified by a lack of sea ice, researchers say that declining sea ice cover is already adding to coastal erosion in the Arctic. A recent study by Irina Overeem and colleagues at the University of Colorado showed that as the period of open water along the coast of the Beaufort Sea has grown longer, the rate of coastal erosion has sped up. For more on coastal erosion, see the Icelights article, Sea ice and the Arctic coast.

References

http://www.washingtonpost.com/blogs/capital-weather-gang/post/historic-alaska-storm-to-produce-hurricane-conditions/2011/11/08/gIQAaiqy0M_blog.html

Earth Observatory: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=76382

Overeem, I., R.S. Anderson, C.W. Wobus, G.D. Clow, F.E. Urban, and N. Matell. 2011: Sea ice loss enhances wave action at the Arctic coast. Geophysical Research Letters, 38, L17503, doi:10.1029/2011GL048681.

 

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