Climate model is first to study climate effects of Arctic hurricanes

EurekAlert: Though it seems like an oxymoron, Arctic hurricanes happen, complete with a central "eye," extreme low barometric pressure and towering 30-foot waves that can sink small ships and coat metal platforms with thick ice, threatening oil and gas exploration. Now climate scientists at the University of Massachusetts Amherst and in England report the first conclusive evidence that Arctic hurricanes, also known as polar lows, play a significant role in driving ocean water circulation and climate.

Results point to potentially cooler conditions in Europe and North America in the 21st century than other models predict.

Geoscientist Alan Condron at UMass Amherst and Ian Renfrew at the University of East Anglia, U.K., write in the current issue of Nature Geoscience that every year thousands of these strong cyclones or polar lows occur over Arctic regions in the North Atlantic, but none are simulated by the latest climate prediction models, which makes it difficult to reliably forecast climate change in Europe and North America over the next couple of decades.

"Before polar lows were first seen by satellites, sailors frequently returned from the Arctic seas with stories of encounters with fierce storms that seemed to appear out of nowhere," says Condron, a physical oceanographer. "Because of their small size, these storms were often missing from their weather charts, but they are still capable of producing hurricane-force winds and waves over 11 meters high (36 feet)."

He and Renfrew say that despite the fact that literally thousands of polar lows occur over the Arctic region of the North Atlantic ocean every year, none are simulated by even the most sophisticated climate models. To understand the importance of these storms on climate, Condron and Renfrew therefore turned to a new, state-of-the-art climate model to simulate the high wind speeds associated with these "missing" storms.

"By using higher resolution modeling we can more accurately simulate the high wind speeds and influence of polar lows on the ocean," Condron says. "The lower-resolution models currently used to make climate predictions very much miss the level of detail required to accurately simulate these storms."....

This photo-like image of a subtropical storm was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on November 1, 2006. Located 900 miles off the coast of Oregon in the northwestern Pacific, this storm system looks like a hurricane, but it is located far from any of the typical hurricane formation areas. The storm originally formed from a cold-cored extratropical storm, but after sending two days over anomalously warm water, it developed a warm center and the hurricane characteristics of a cloud-free eye and an eyewall of thunderstorms circling the eye. Though the storm was strong enough to be named had it formed in one of the hurricane sectors, it is outside the regions which hurricane monitoring organizations administer, so the authority to give it a full name is not well defined. As of November 2, 2006, the Central Pacific Hurricane Center in Honolulu had not issued any information on the storm nor even applied it with a name. It was known merely as Storm 91C by the U.S. Navy.