Even though the entire globe has warmed over the last few decades, the Arctic has seen the greatest changes in temperatures. One of the clearest readouts of that change has been the sea ice that fills the Arctic ocean each winter. Although the exact extent of its summer time melting varies from year to year, there's been a sharp downward trend in the amount of ice left each September. But, as the Arctic enters all-day darkness in the winter, most of the ocean freezes over again—all the excitement's in the summer.
This year, however, unusual winter warmth at the fringes of the icepack have led to a very odd freeze-up, and a record low for the maximal ice extent. The largest extent of ice coverage, 14.54 million square kilometers, was over a million square kilometers below the long-term average. Normally, the peak of the freeze-up occurs in March; this year, ice extent started dropping in late February before stabilizing over the last two weeks. That excursion took it outside of two standard deviations of the 1980-2010 average ice extent.
The National Snow and Ice Data Center, which tracks these things, says that there may be further freezing at this time of year. But, unless that freeze is extreme, ice levels are unlikely to get back to where they were in February.
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