I’ve waited until the NSIDC released their Arctic Sea Ice News & Analysis report for February instead of posting something one month after my last post, then waiting for the NSIDC’s report to fill in some of the blanks in my discussion. From now on, I’ll wait for their reports to come out before posting.
The state of polar sea ice in February 2010 is bad compared to climatological conditions (1979-2000). The global sea ice extent continues to track well below climatological values, as this graph demonstrates. The most recent data show that global sea ice covers ~15.5 million sq. km., compared to 16 million sq. km. normally. That’s a recovery of 500,000 sq. km. from January, but still below average conditions. As I wrote last month, the last two times the annual minimum didn’t fall below climatological norms were in 2008 and 2004. In a nutshell, the annual minimum extent has shifted in behavior in a significant way in the last decade.
The state of Arctic sea ice in January 2010 continues to be poor relative to climatological norms. The areal extent of Arctic sea ice has been below -2 standard deviations since late June 2009. Recent conditions have resulted in a late cool season surge in sea ice areal extent. During January, the Arctic Oscillation was at its most negative phase in decades. This allowed cold air to pour out from the Arctic into North America, Europe and Russia. This combined with the more southerly jet stream due to the moderate El Nino helped set up intense storm systems over the eastern U.S. as well as many countries in Europe. At the same time, warmer air than normal was found over the Arctic. Sea ice had a harder time overall developing. Wind patterns were established that prevented ice from flowing out from the Fram Strait. This is potentially good news for this year’s Arctic sea ice since its volume could grow while staying in one place for months. The older and more voluminous the ice, the better chances it has of sticking around through this year’s melt season.
The recent surge in Arctic sea ice extent has occurred in the Bering Sea. This is important because the Atlantic sector remains well below average for this time of year. This surge is likely to be the Arctic’s last for this winter season. The maximum extent will likely be reached between today and the next couple of weeks, after which the sea ice melt season begins. Today’s current extent is slightly higher than the yearly maximum reached in 2005-07 and ~500,000 sq. km. less than the maxima reached the past two winters. Again, the current areal extent isn’t necessarily this year’s maximum value – determination of that will occur in a few weeks’ time.
The average ice extent for February 2010 was 14.58 million sq. km., the fourth lowest since 1978, when satellite records began. That extent was 220,000 sq. km. more than the record low extent set in 2005. Since 1978, the Arctic sea ice extent in February has decreased at 2.9% per decade.
The state of Antarctic sea ice in February 2010 is slightly above average relative to climatological norms. The areal extent of Antarctic sea ice has been between average and +2 standard deviations in the past month. In the past week or so, the areal extent has been larger than it was in the middle of the month. This could indicate that, in a similar but reverse fashion in the Arctic, the yearly minimum might have been reached already. That should become clearer in the next week or so, as climatologically the sea ice begins to grow again starting in March.
The difference between the state of sea ice in the Arctic and Antarctic regions on an annual basis can be attributed to a couple of different physical phenomena. The Antarctic ice extent has remained within climatological norms in recent years because of the damage to the ozone layer caused by people in the 20th century. That might not make intuitive sense at first – I know it didn’t for me. Here’s what has happened: as ozone was destroyed (and has remained low each austral winter and spring) on a widespread basis, the circulation of the stratosphere was changed. These changes caused cooling to occur between the ground and the stratosphere. So near-surface temperatures over Antarctica are cooler than they would be if no damage to the ozone layer had occurred. These cooler temperatures have helped sea ice actually increase in extent.
In contrast, the Arctic region is experiencing the effects of people’s growing influence on the climate system. Atmospheric temperatures have increased faster over the Arctic than any other region on Earth. Those temperatures are expected to continue to increase since we’re not even slowing down our greenhouse gas pollution emissions. Now, denialists will interpret that to mean scientists are predicting no ice in the Arctic, even in the winter. No such claims have been made in the refereed journals. What scientists have said is that boreal (Northern Hemispheric) summers could eventually see a drastic decline in sea ice – possibly to the point where for all purposes, no sea ice could be in the Arctic Ocean in the summer. Research done in the last part of the 20th century indicated that potential date was still quite a ways off – about a century or so. More recent research has indicated there is a significant chance that a summer-time ice-free Arctic could be seen by 2030 – only 20 years away now. Such an occurrence would have significant effects on the rest of the climate system. Instead of reflecting most of the incoming summer sunlight back into space, that energy would be absorbed by a blue ocean. That would cause the heat content of the globe’s oceans would increase faster than they have to date. Winter ice would still form, but the extent would likely be less than what we’ve seen in the past 10 years. That’s significant.
Pictures and Graphs
Here is a satellite representation of Arctic sea ice conditions from yesterday:
For comparison purposes, here is the similar picture from August:
Here is the time series graph of Arctic sea ice extent with the +/- 2 standard deviations as a light-gray envelope around the climatological average through yesterday:
You can find the NSIDC’s February report here. The page is dynamic, so if you’re reading this after March 2010, that month’s report will show up first. If that’s the case, you can look for the February report on the top pull-down tab on the right-hand side of the page.
Here is a satellite representation of Antarctic sea ice conditions from yesterday:
Here is the time series graph of Antarctic sea ice extent with the +/- 2 standard deviations through yesterday:
Cross-posted at SquareState.