The state of global polar sea ice area at the end of February 2011 is troublesome: well below climatological conditions continue to persist (1979-2009). Sea ice in the Arctic continues to track significantly below average, setting a record minimum for the month in the modern era. Antarctic sea ice continued to hover near record low extent values during February. Just as it did during early 2006, global sea ice area has double-dipped during the yearly minimum. Instead of clearly rebounding from that low, as it usually has in the past 40 years, global sea ice is clearly characterized yet again by new conditions. As of this writing, the global area is -1.4 million sq. km. below average.
According to the National Snow and Ice Data Center, Arctic sea ice extent set a record low again in February. Averaged over February 2010, Arctic sea ice extent was only 14.36 million sq. km., tying the record low set in 2005. The NSIDC notes, “Every year since 2004 has had a mean February extent below 15 million square kilometers”. That’s a new state for the Arctic; a state which is looking increasingly permanent. Large areas of the Okhotsk Sea, Greenland Sea, Newfoundland Sea, Baffin Bay and St. Lawrence River remain unfrozen, which is decidedly abnormal for the end of February.
In February, daily Arctic ice extent values remained about 1.1 million sq. km. less than the normal value. This continued the trend that I noted in my post about January conditions. This is the first time on record that the extent has been so low for the first two calendar months of the year. The extent was >500,000 sq. km. lower than during the same period in 2008-2010. Moreover, the last 2 times a calendar year started out anywhere near this negative was in 2006 and 2007. In 2007, the all-time record low ice extent was set. By this time in 2006 and 2007, the ice extent was ~200,000 sq. km. higher than it is during 2011. Does that mean that a new record low extent will be set this year? Not necessarily. 2007 witnessed weather conditions that helped ice flow out of the upper Arctic and into warmer waters, where it melted. That hadn’t happened prior to 2007 in the satellite era, nor has it happened since. I will say this, however: the longer the extent remains so abnormally low, the less extreme weather conditions will have to be during this upcoming summer to generate record low conditions again. A lot of young, thin ice currently resides in the Arctic. It won’t take as much as it did in the past to melt the ice this year.
The change in February ice extent has been measured at -3.0% per decade by the NSIDC. What that means is as of the end of February 2011, the Arctic has only 14.36 million sq. km. of sea ice extent, while as of the end of January1978, the Arctic had 16.4 million sq. km. of sea ice. That difference is real and it is significant.
Arctic Pictures and Graphs
Here is a satellite representation of Arctic sea ice conditions from March 2nd centered on Hudson Bay:
And here is a satellite representation of Arctic sea ice conditions from March 2nd centered on the Bering Sea:
Compare these with February 7th’s satellite representation, centered on the North Pole:
It’s easy to see where shorter-term climatic oscillations and this season’s weather conditions have worked to prevent sea ice from forming on this month’s satellite representations. That being said, the Arctic Oscillation has switched from being extremely negative to positive in the past few weeks. What this means is cold air is being bottled up near the Arctic Circle instead of rushing south over the eastern U.S. and Europe. This could allow for a late season freeze-up of ice around the periphery of the current ice pack. Next month’s post will take another look at those conditions.
As a whole, here is what the Arctic ice extent looks like in time-series form through March 2nd:
The NSIDC has included the 2006-2007 time-series line as a useful comparative measure for this year’s extent. 2007 witnessed the smallest areal extent covered by Arctic sea ice in the modern era. It obviously remains unknown at this time whether this September’s extent will challenge 2007′s for the record low. But I’ll mention this again: a lot of the ice in those satellite representations are only a few months old. They face warmer conditions in the ocean and in the lower atmosphere than any Arctic sea ice has in tens of thousands of years. As each year passes, that becomes more evident as these time-series lines track far, far below average conditions of just a few decades ago.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from March 2nd:
For comparison purposes, here is the similar picture from February 7th:
Sea ice conditions haven’t changed that much in the past month. I haven’t seen anything yet regarding the ice shelves ringing the continent. The longer there is no news, the better, since those shelves keep the land-based ice on land and not allowing it to escape to the sea.
Here is the time series graph of Antarctic sea ice extent with the +/- 2 standard deviations in light gray and the climatological mean in dark gray through March 2nd:
After a torrid pace of ice melting in January, little ice was left to melt in February. That combined with continued cooler than normal conditions on the east side of the Antarctic Peninsula and off the coast of West Antarctica meant melting drastically slowed down through February. In fact, during the last week of February, conditions have shifted and now ice is refreezing. After hugging the bottom of the 2 standard deviation envelope for over a month, Antarctic sea ice extent is slowly edging back toward the mean extent value.
You can find the NSIDC’s March report here. The page is dynamic, so if you’re reading this after March 2011, that month’s report will show up first. If that’s the case, you can look for any report in their archive on the top pull-down tab on the right-hand side of the page.
Cross-posted at SquareState.