Scientists at NASA and the National Snow and Ice Data Center published research last week in the Journal of Geophysical Research based on satellite microwave data of seasonal Arctic ice thaw from 1970 to 2009. The study indicates the seasonal Arctic sea ice melt season is now about 20 days longer than it was 30 years ago.
The growing season of thaw is most pronounced in Arctic waters off the coasts of Alaska and Canada, including the Chukchi and Beaufort seas, where the season is 30 days longer now than in 1979. East Greenland and the Hudson Bay also share nearly a month longer of seasonal melt. The Hudson Bay exhibits one of the fastest increases in seasonal melt on the globe.
On average, seasonal melt has increased about 2.5 days per decade and lasts 3.7 days longer - an average of just under 20 days since 1979.
"With the exception of the Sea of Okhotsk, all areas in the Arctic show a trend toward earlier melt onset and also a trend toward later freezeup," researchers said in their published report.
Scientists suggest that the longer melt season creates a feedback loop further accelerating warming in the region. When the ice melts, darker ocean water absorbs more heat from the sun. With a longer melt season there is more time for these dark waters to absorb more heat, adding further to ice loss. The delayed fall freeze also means thinner ice reforms every season, leading to increased ice loss in the coming thaw next season.
NASA has recently published research showing that average thickness of Arctic sea ice shrank 2.2 feet between the winters of 2004 and 2008, with the surface area covered by multi-year ice shrinking by more than 42 percent.
As goes the ice in the Arctic waters so goes conditions on land. The National Oceanic and Atmospheric Administration said the changes observed in sea ice leads changing conditions on land. Those changes include warmer fall temperatures, making was for a northward march of trees and shrubs into areas that were once frozen tundra. The changing patterns on land and sea rise up into the atmospheric circulation patterns in northern Alaska and Canada, all the way down to mid-latitude North America.