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Record low December Arctic ice extent
The December Arctic sea-ice extent was at its lowest level for that month since Arctic satellite observations began in 1979, the National Snow and Ice Data Center reported Jan. 5. The average area of 4.63 million square miles of sea ice was 104,000 square miles less than the previous record low for December, set in 2006, and continued a trend of December ice loss of 3.5 percent per decade.
In something of a rerun of a weather pattern seen last winter, an extreme negative phase of a weather phenomenon known as the Arctic oscillation resulted in higher-than-normal atmospheric pressures in the Arctic, causing circumpolar winds to slacken and allowing cold air to slide south into lower latitudes than normal, leading to frigid winter conditions in northern Europe and severe winter storms down the East Coast of North America.
High Arctic temperatures But this abnormal air-flow pattern in the northern hemisphere, coupled with warming from unfrozen areas of ocean, resulted in higher than normal temperatures over large areas of the Arctic, slowing and at times halting the annual freeze up of the sea ice. The ice cover is especially low in Hudson Bay, Hudson Strait and Davis Strait, on the northeast side of Canada, NSIDC said.
In the past a negative phase of the Arctic oscillation has helped preserve old sea ice during the winter, and has resulted in an increased ice cover at the end of the summer, NSIDC said. But this pattern appears to be changing, with winds resulting from the oscillation in the winter of 2009-10 shifting much old ice into the southern Beaufort and Chukchi seas, where the ice later melted during the summer thaw.
“It may be that with a warmer Arctic, old rules regarding links between the atmospheric pressure patterns and sea-ice extent no longer hold,” NSIDC said.
—Alan Bailey
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