Arctic Ice Extent has Reached its Limit: Lowest on Record

With winter at its end, it appears that the extent of Arctic sea ice has reached its limit. Worryingly, it's the lowest extent ever seen, reaching only about 5.61 million square miles. What's more, this is also one of the earliest maximum extents ever reached, with most seen much further into the end of the season.

Arctic sea ice is pretty self explanatory: it's frozen seawater that grows on the surface of the Arctic Ocean between fall and winter, and gradually recedes at the end of this period. For as long as NASA, the NOAA, and other organizations have been able to monitor it, they have traditionally seen the ice reach its annual maximum and start to recede right about now (March). The average date between 1981 and 2010 in particular was March 12, according to the US National Snow and Ice Data Center. That's what makes this year's extent so unusual. It had started to recede as early as February 25, from the smallest maximum ice coverage ever seen.

According to NASA, this 2015 max extent, if it remains where it is, is about 50,000 square miles below the previous lowest peak wintertime extent, which occurred in 2011 at 5.66 million square miles.

That's not a terrible difference, but the space agency is quick to point out that this could hint at a more worrying trend where the Arctic summertime ice minimum continues to shrink at an alarming rate. Currently, the record low of 2012 (~ 1.3 million sq mi) dropped by more than 18 percent since the previous minimum, seen in 2007. (Scroll to read on...)

[Credit: NASA's Goddard Space Flight Center/J. Beck]

"The winter maximum gives you a head start, but the minimum is so much more dependent on what happens in the summer that it seems to wash out anything that happens in the winter," Walt Meier, a sea ice scientist at NASA's Goddard Space Flight Center, explained in a recent statement. "If the summer is cool, the melt rate will slow down. And the opposite is true, too: even if you start from a fairly high point, warm summer conditions make ice melt fast. This was highlighted by 2012, when we had one of the later maximums on record and extent was near-normal early in the melt season, but still the 2012 minimum was by far the lowest minimum we've seen."

And while Meier calls the winter maximum not as scientifically interesting or important as the minimum, it is still an important factor for conservationists who are currently trying to predict how and when Arctic ecosystems are going to experience some radical change.

As things stand, polar bears in the Arctic are rapidly losing the sea ice that they traditionally use to hunt. If the extent of this ice continues to shrink over both key seasons, the critically endangered animals may disappear from the wild even sooner than the bleak projections that already exist indicate.

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