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article imageArctic winter sea ice extent is seventh lowest on record

By Karen Graham     Mar 21, 2019 in Environment
Arctic sea ice has reached its maximum extent for the year, peaking at 14.78 million square kilometers on March 13. It is the joint seventh smallest winter maximum in the 40-year satellite record – tied with 2007.
The announcement came from the NASA-supported University of Colorado's National Snow and Ice Data Center (NSIDC) and NASA on Wednesday.
"While this is not a record low for the Arctic sea ice maximum extent, the last four years have been the lowest in our record, reflecting a downward trend in winter sea ice extent," NSIDC senior research scientist Walt Meier said in a statement.
Sea ice extent on March 13  2019
Sea ice extent on March 13, 2019
The Arctic sea ice cover is an expanse of frozen seawater floating on top of the Arctic Ocean and its surrounding seas. It thickens and expands during the fall and winter months. The Arctic's sea ice reaches its maximum yearly extent during a period between late February and early April.
The sea ice then thins and shrinks during the spring and summer months until it reaches its annual minimum extent in September.
Despite these seasonal changes in the Arctic sea ice, the extent of the sea ice has been dropping during both the growing and melting seasons over the last 40 years. This year's low extent was not as low as the preceding four years that started in 2015, but this does not mean the Arctic is recovering.
"The temperatures in the Arctic were a bit higher than average and we saw a lot of ice loss in the Bering Sea, but nothing this winter was as extreme or dramatic compared to recent years and the record lows," Meier said.
The loss of Arctic sea ice is not only a consequence of global warming  but also an accelerant when ...
The loss of Arctic sea ice is not only a consequence of global warming, but also an accelerant when millions of square kilometres of snow reflecting the Sun's radiation back into space are replaced with dark blue ocean that absorbs it instead
One problem that has persisted is the melting of multiyear ice, the older and thicker ice that acts as a wall against melting for the rest of the sea ice cover. This wall has essentially disappeared.
A 2018 study led by Ron Kwok, a sea ice researcher with NASA's Jet Propulsion Laboratory in Pasadena, California, found that 70 percent of the sea ice pack consists of "seasonal" ice that melts during the following summer.
"The large changes in ice coverage associated with the loss of the multiyear ice pack have already occurred," Kwok said. "The seasonal ice now represents a larger fraction of the Arctic sea ice cover."
"Because this young ice is thinner and grows faster in the winter, it is more responsive to weather and makes the sea ice cover respond differently than before. It's not that we won't see new wintertime or summertime record lows in the next years—it's just that the variability is going to be higher."
More about Arctic, sea ice extent, winter 2019, seventh lowest on record, Climate change
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