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Environment

Arctic Sea Ice Could be Heading for a New Low

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The extent of Arctic sea ice has been particularly low in the Sea of Okhotsk. In the animation above, the pink indicates areas where NASA's Terra satellite detected sea ice on March 5, 2015. The orange line shows the long-term median extent of the ice in this region. I've removed the overlays in the animation's second frame so you can see what the ice looks like from space. (Images: NASA Worldview. Animation: Tom Yulsman) |Note:See updates below.| In the ten days between February 25th and March 7th, swaths of sea ice floating across an area of the Arctic the size of Washington state simply vanished. This sharp drop in Arctic sea ice, following on from a particularly low extent in February, may be a harbinger of a new record: the lowest maximum winter extent for Arctic sea ice in the satellite era. Each year at the end of the warm season, falling temperatures cause ice to form atop Arctic waters and spread ever more widely during winter. The geographic extent of this ice typically reaches a maximum in the first or second week of March. After that, warming temperatures inexorably cause it to shrink until a minimum is reached, typically in September. Thanks to human-caused global warming — which has affected the Arctic strongly — both the maximum winter extent of sea ice, and the minimum extent at the end of the warm season, have been getting smaller and smaller over the years.

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Source: NSIDC February saw the third lowest extent of Arctic sea ice for the month. On February 25th, the ice actually stopped growing and began shrinking — two or three weeks before the long-term average peak. (Click on the thumbnail image at right for the details.) In fact, between the 25th and March 7th, sea ice coverage shrank by 175,000 square kilometers, or 67,568 square miles. That's slightly smaller than Washington state. One caveat is in order: In 2012, and 2014, Arctic sea ice rallied during much of March, growing in extent past the usual peak. And it's entirely possible that this will happen over the next few weeks. We'll just have to wait and see.

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But it's already clear that particularly warm temperatures in some parts of the Arctic have had significant effects. One of those areas is the Sea of Okhotsk, in Russia's far northwest. (Update 3/9/15: Click on the thumbnail at left for a graphic showing abnormally warm temperatures in that part of the world.) The animation at the top of this post shows sea ice coverage in the region on March 5th, as detected by NASA's Terra satellite. That's the pink area in one frame of the animation. I've also drawn an orange line indicating the long-term average edge of the sea ice for this time of year. So as you can see, the ice coverage in the Sea of Okhotsk is particularly low. (I also included a second frame in the animation so you can see more clearly what the sea ice itself looks like from space.) This is not the only area of low extent. In its February report, the National Snow and Ice Data Center noted this:

While low extent for the Arctic as a whole was largely driven by conditions in the Sea of Okhotsk and the Bering Sea, extent was also slightly below average along the Barents Sea and parts of the East Greenland Sea.

To my non-expert eyes (and that's an important caveat), things are not looking so promising for a rebound:

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This animation shows how the extent of Arctic sea ice has changed between late February and March 7th. I created the animation above to provide a broader overview of what has happened to sea ice in the past 10 or so days. On one of the frames, I've circled the Bering Sea to the left, and the Barents Sea to the right. (Caveat: The Barents Sea circle does extend somewhat into the Arctic Ocean.) Keep an eye on what happens in those regions between February and March 7th. It's pretty obvious, right? Dramatic shrinkage of sea ice in those areas — when it should still be growing. True, it does grow in some other places. But that doesn't make up for the losses. | Update 3/9/15: Bob Henson has an excellent post up at Weather Underground on what's happening to Arctic sea ice right now. Check it out here| Whenever I write about Arctic sea ice, I usually get comments from people who point out that while this is happening in the Arctic, sea ice coverage in the Antarctic is actually expanding. These comments reflect claims by prominent climate change doubters like Christopher Monckton, who has written this:

In fact, the global sea-ice record shows virtually no change throughout the past 30 years, because the quite rapid loss of Arctic sea ice since the satellites were watching has been matched by a near-equally rapid gain of Antarctic sea ice. Indeed, when the summer extent of Arctic sea ice reached its lowest point in the 30-year record in mid-September 2007, just three weeks later the Antarctic sea extent reached a 30-year record high. The record low was widely reported; the corresponding record high was almost entirely unreported.

It should be noted that in 2012, the summer extent of Arctic sea ice reached an even lower point. But regardless, Monckton's point is that the overall amount of sea ice has remained the same. And he is wrong:

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Arctic and Antarctic Sea Ice Extent Anomalies, 1979-2012. Thick solid lines indicate 12-month running means, the dashed lines indicate the trends. Thin lines indicate monthly anomalies, meaning departures from the long-term mean. (Source: NSIDC) As this graphic shows, Arctic sea ice extent declined sharply from 1979 to 2012. It's true that in the Antarctic, sea ice did increase — but only slightly, and not enough to offset the losses in the Arctic. Recent research shows that the global extent of sea ice — taking into account both hemispheres — has been declining at a rate of 1.47% per decade (± 0.25% decade). Moreover, despite the increases in Antarctic sea ice extent, the overall decline globally is actually speeding up. We'll know in a few weeks whether the Arctic has set a new record. I'll post an update when the verdict is in.

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