极地飓风比想象中频繁

From 2000 to 2010, about 1,900 cyclones churned across the top of the world each year, leaving warm water and air in their wakes -- and melting sea ice in the Arctic Ocean. That's about 40 percent more than previously thought, according to a new analysis of these Arctic storms.

A 40 percent difference in the number of cyclones could be important to anyone who lives north of 55 degrees latitude -- the area of the study, which includes the northern reaches of Canada, Scandinavia and Russia, along with the state of Alaska.

The finding is also important to researchers who want to get a clear picture of current weather patterns, and a better understanding of potential climate change in the future, explained David Bromwich, professor of geography at The Ohio State University and senior research scientist at the Byrd Polar Research Center.

The study was presented on Dec. 12 at the American Geophysical Union meeting, in a poster co-authored by his colleagues Natalia Tilinina and Sergey Gulev of the Russian Academy of Sciences and Moscow State University.

"We now know there were more cyclones than previously thought, simply because we've gotten better at detecting them," Bromwich said.

Cyclones are zones of low atmospheric pressure that have wind circulating around them. They can form over land or water, and go by different names depending on their size and where they are located. In Columbus, Ohio, for instance, a low-pressure system in December would simply be called a winter storm. Extreme low-pressure systems formed in the tropical waters can be called hurricanes or typhoons.

How could anyone miss a storm as big as a cyclone? You might think they are easy to detect, but as it turns out, many of the cyclones that were missed were small in size and short in duration, or occurred in unpopulated areas. Yet researchers need to know about all the storms that have occurred if they are to get a complete picture of storm trends in the region.

"We can't yet tell if the number of cyclones is increasing or decreasing, because that would take a multidecade view. We do know that, since 2000, there have been a lot of rapid changes in the Arctic -- Greenland ice melting, tundra thawing -- so we can say that we're capturing a good view of what's happening in the Arctic during the current time of rapid changes," Bromwich said.