During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Because of the demise of AMSR-E the IJIS sea ice extent (SIE) numbers are no longer central to these updates. Instead I now use Cryosphere Today sea ice area (SIA) numbers and compare them to the SIA numbers in the 2005-2011 period. NSIDC has a good explanation of sea ice extent and area in their FAQ. I also look at other things like regional sea ice area, sea ice extent, temperature and weather forecasts, anything that can be of particular interest. Check out the Arctic sea ice graphs webpage for daily updated graphs, maps and live webcam images.
April 22nd 2012
A new year, a new spring, a new melting season. After a very deceptive/instructive end of the winter season the Arctic sea ice is off to an extremely slow start. Of course there already were above average conditions in regions like the Bering Sea and Baffin Bay, and when two weeks ago a big high pressure system in the middle of the Arctic got a huge clockwise gyre going,the ice pack was pushed into the big, empty expanse on the Atlantic side of the Arctic (see Novaya Zemlya April 2012). But because temperatures are still quite low at this time of the year, the ice pushed southwards didn't melt and the leads that were created elsewhere quickly froze over.
Conditions have turned this year into a copy of 2010, worse even, with extent and area numbers approaching the long-term averages. Whether the situation remains like this, or whether trend lines start falling of a cliff like they did in 2010, is the first big question of the melting season.
Without further ado, let's have a look at the numbers.
Sea Ice Area (SIA)
Here's the current SIA graph based on CT data:
The 2012 trend line is clearly jutting out. SIA had been going down very hard in the first week of April, but since then we have seen a substantial slowdown, with lots of days of SIA increase. The numbers make it more than clear that 2012 is behind all the other years in the 2005-2012 period, and thus 8th out of 8 years.
The current difference between 2012 and the other years is as follows:
- 2005: +472K (-31,277)
- 2006: +488K (-37,327)
- 2007: +903K (-30,747)
- 2008: +699K (-41,979)
- 2009: +121K (-37,793)
- 2010: +236K (-48,659)
- 2011: +416K (-44,019)
Between brackets is the average daily area decrease for the month of April. 2012's average daily area decrease for April is currently -33,816 square kilometers.
On the Cryosphere Today SIA anomaly graph we clearly see how close 2012 is brushing against the long-term average:
The regional SIA graphs confirm the reasons for the total SIA number being so high. The Arctic Basin, Kara Sea and Greenland Sea saw a late extra increase, whereas especially the Bering Sea is still anomalously high.
Sea Level Pressure (SLP)
During the melting season and the freezing season looking at weather maps and forecasts can be a big help in determining what is going on up north. However, it becomes a tad more difficult in the transition periods between the two seasons. Winds blowing the ice away somewhere that leave an open patch of sea water during the melting season can still get frozen over in the transition period. But that doesn't mean we can't have a look to see if we can make sense of what has happened and will happen in the short-term.
So here's an animation of SLP images from the DMI Centre for Ocean and Ice of the past three weeks. DMI has improved these SLP images by showing the isobars over land as well, which is very helpful:
This underscores my point: that huge high pressure system over the central Arctic would have caused substantial decreases in summer, but in the current transition period it actually slowed down SIA/SIE decrease.
So even though it doesn't tell us much, I've made this animation of the ECMWF forecast for the coming 5 days (click for a larger version):
There's a low moving near the Bering Sea, which will push the ice southwards, but as we have been seeing in the past couple of days on the Uni Bremen sea ice concentration maps the patches of open water aren't freezing up as fast as they did this past winter. A low near Baffin Bay should start compacting the ice there, and I'm not sure what the effect of the high forming over the Kara Sea will be. But all in all I would expect a faster decrease than witnessed in the past 10 days.
This year the melting season will be covered for the third time on the Arctic Sea Ice blog. I hope everyone will enjoy watching, analyzing, forecasting and speculating together, and frankly, I don't see how we won't.
PS These (bi-)weekly updates of course take over the function of the winter open threads.