Think Alaska is too cold for you? Well, it seems that average fall temperatures there are increasing at a rapid rate. The most northerly community in the U.S., the town of Barrow, Alaska, has recorded an incredible 12.96 degree Fahrenheit (7.2 degrees Celsius) increase in its average October temperature over the 34 years from 1979 to 2012. The team from the University of Alaska Fairbanks who made the discovery also observed that the most notable average temperature increases in summer and fall correlated with significant losses in sea ice concentrations.
During the 34-year period studied, the average annual temperature for Barrow increased by 4.86 Fahrenheit (2.7 degrees Celsius), but what was most striking was the spike in average temperatures in fall and to a lesser extent in summer. Lead author of the study Gerd Wendler told the Alaska Dispatch News, “I was actually astonished about it. I think I have never, anywhere, seen such a large increase in temperature over such a short period.” The team believes the reason for the increase in seasonal temperatures is the decreasing sea ice cover in the corresponding seasonal period, which means ocean winds are not kept cool as they blow over the ice, but instead are warmed by the water and increase the temperature on dry land as they blow onshore. “You cannot explain it by anything else,” Wendler added. The study notes that by October, the sun is already low in the sky and therefore unlikely to be a contributing factor to the warmer averages.
In their abstract, the team reports: “October displayed the greatest change; the amount of open water increased by 44% and 46% for the Beaufort and Chukchi Seas, respectively. The large amount of open water off the northern coast of Alaska in autumn was accompanied by an increase of the October temperature at Barrow by a very substantial 7.2°C over the 34 year time period. Over the same time period, Barrow’s precipitation increased, the frequency of the surface inversion decreased, the wind speed increased slightly and the atmospheric pressure decreased somewhat.”
The study period commenced in 1979 because that was when reliable satellite data for sea ice concentration became available. When the team went back further in time, they found that the 1920s were a particularly warm decade (in fact, The Washington Post published an article on 2 November 1922 entitled “Arctic Ocean getting warm, seals vanish and icebergs melt,” which shows just how warm it was). Taking the longer period into account, the average annual temperature increased by 2.72 degrees Fahrenheit (1.51 degrees Celsius) over 91 years, so the current increase is both rapid and recent. The team notes that if the trend of decreasing sea ice continues it will make the area more like the Bering Sea, but will also put the Alaskan coast at increased risk of erosion from intensified wave activity.
Photos by NASA/Kathryn Hansen via Flickr