Study: Alaska got colder from 2000-2010
01/07/2013 5:55 AM
01/07/2013 7:02 AM
The overwhelming majority of Alaska is getting colder and has been since 2000, according to a study by researchers with the Geophysical Institute at the University of Alaska Fairbanks. But the authors stop short of saying the lower temperatures contradict that idea that the earth, and Alaska in particular, is warming. Instead, they conclude that the findings show a temporary variation.
The scientists with the Geophysical Institute's Alaska Climate Research Center looked at temperatures recorded at 20 "first-order meteorological stations" in Alaska from 2000 to 2010. The stations were spread from Annette in Southeast to Barrow on the Arctic Ocean to Cold Bay at the southwest tip of the Alaska Peninsula. All are operated by professional meteorologists with the National Weather Service, use similar or identical equipment and follow uniform operating procedures.
Every station pointed to a cooling trend, except Barrow.
The mean cooling for the average of all 20 stations was 2.34 degrees Fahrenheit. The chilling trend was most pronounced in the Bering Sea region, with King Salmon recording a drop of 4.42 degrees in the first decade of the new century.
The Anchorage average went down by 2.7 degrees over the 10 years, Fairbanks lost about 1.8 degrees and Southeast stations dropped by a degree or less.
The report, produced by a team headed by professor emeritus of geophysics Gerd Wendler, is titled "The First Decade of the New Century: A Cooling Trend for Most of Alaska." It was published in The Open Atmospheric Science Journal, 2012.
A map in the report traces a line across the top of Alaska, starting at Point Hope and generally running across the crest of the Brooks Mountain Range to Canada. All portions of the state south of that line recorded colder temperatures and all places north recorded warmer.
The authors looked into sunspot activity and determined that it was not related to the trend. They did find a correlation with the Pacific Decadal Oscillation, or PDO, a shift in warm waters from the eastern to the western side of the Pacific Ocean not unlike the El Nino warming pattern. But while El Nino shifts over months, the PDO moves much more slowly, staying put for years or decades.
Wendler has previously taken part in research that showed that a long warming period in Alaska, starting in 1977, was influenced by the PDO.
The PDO affects the ongoing low pressure system -- or "semi-permanent cyclone" -- in the Aleutians. In the present configuration, the PDO is causing the Aleutian Low to weaken. That means decreased wind speeds, resulting in less warm air from south of the Aleutians mixing with colder air in the Bering Sea, which leads to chillier temperatures on the west coast of the state.
The Arctic Ocean coast, far from the Aleutians, is not significantly affected by this phenomenon. Barrow showed an increase of 3.04 degrees over the decade, which the authors called substantial.
The report notes previous cooling periods, including a span of some 30 years that began in the 1940s, and says it is too early to decide whether the widespread Alaska cooling trend "is a climatic shift" or merely a blip. Its summary reads: "The long term observed warming of Alaska of about twice the global value. . . . is sometimes temporarily modified or even reversed by natural decadal variations."
The authors acknowledge, however, that the overall statewide drop of 2.34 degrees is a lot for one decade.
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