Warming temperatures possibly increased the frequency of extreme Arctic cyclones between the 19th and 21st centuries, a finding that highlights concerns about climate impacts in the future and coastal erosion in the polar north, according to new research.
The paper in Geophysical Research Letters used climate models to peer back in the past and found that there was a statistically significant change in both sea-level pressure and extreme Arctic cyclone activity between the mid-1800s and 2005. Because warming temperatures can lower sea-level pressure, a factor associated with cyclones, there is a good probability that there is a climate change link with the storms, said Stephen Vavrus, a scientist at the University of Wisconsin, Madison, and author of the study.
"What is unique about this study is that it goes all the way back to the 1850s," said Vavrus. Most prior research on the response of cyclones has not focused on polar regions, as well, the study added.
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Vavrus found that extreme cyclones increased by roughly two to three per decade at maximum, starting around the 1850s. There was a simultaneous significant drop in sea-level pressure -- or atmospheric pressure at sea level -- during the same time frame through 2005.
For the most sensitive Arctic locations, that would mean roughly an increase from about 10 extreme cyclones per decade in the 1850s to about 40 per decade by the end of the 20th century, he said.
Warming can cause a decline in sea-level pressure, as warmer air is lighter, explained Vavrus. While the future remains uncertain, it is possible that ongoing warming temperatures in the Arctic could continue to boost the frequency of very large cyclones in the region, he said.
If that happened, it could create problems for coastal erosion, in particular, near Arctic communities.
"This is a problem already. As we lose ice cover along the coast, you would expect to see higher waves. On top of that, with more intense cyclones, then you have a double whammy," he said.
How stronger storms increase ice loss
Massive Arctic storms also can exacerbate ice loss spurred by warming, if they hit at the right time and location. Scientists partially attribute record ice lows in 2012, for instance, to a powerful storm in August that helped disperse warm water around the Arctic.
The Arctic has warmed by as much as 2 to 3 degrees Celsius per decade since 1960 in areas of high warming, according to the National Oceanic and Atmospheric Administration. An important consideration is that the research does not document changes after 2005, when sea ice loss reached record proportions, the study said.
However, two scientists not involved with the research cautioned that it is too early to make definitive conclusions about the frequency of Arctic cyclones in the future amid a warming climate.
The paper concludes "maybe" about the link between climate change and the frequency of big storms, said Eric Steig, a professor at University of Washington. He said the research is distinctive in showing that climate models -- as opposed to weather forecast models -- can simulate cyclones in the past.
Real-world data about Arctic cyclones became available around the 1950s, and even then, there is some disagreement about storm frequency, noted David Bromwich, senior research scientist at the Byrd Polar Research Center at Ohio State University.
Models peer backward in time
It's quite possible that the detected cyclone activity in the past is too conservative, considering that climate models tend to underestimate the level of actual ice loss in the Arctic, said Bromwich. A similar dynamic could be going on with the cyclones, he said. He co-authored research this year finding that there were 40 percent more Arctic small and large cyclones than previously believed between 2000 and 2010.
"We need more effort on understanding precisely what's been happening as far as the real world goes, so we have a better basis for comparing with the climate models," he said.
Still, Vavrus said his study offers a warning about the future, as scientists predict that climate change will cause Arctic-wide decreases in sea-level pressure. Low sea-level pressure is a side effect of cyclones, much in the same way that increases in average summer temperature are linked with more extreme heat waves, said Vavrus.
"Although it's possible to get a decrease in average sea-level pressure without an increase in extreme cyclones, just as it's possible for the average summer temperature to increase without more extreme heat waves; in both cases, the response of the average and the extremes is more likely to go hand in hand," Vavrus said.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
