I think this winter is going to get studied like crazy,
for quite a while. It’s a very interesting time.
Jennifer Francis, Washington Post
The extraordinary temperature anomalies in the Arctic since the start of the year haven't gone unnoticed in quite a few media outlets, and I apologize for not having joined the fray of actuality. On the other hand, context trumps actuality, as we need to compare to previous years and get a feel for what this prelude to the melting season may mean. In that sense, I'm early with this year's winter analysis (compared to last year).
Let's start studying like crazy, shall we?
It's a lot of text and images, so if you're feeling a bit tl;dr-ish today,
skip to the conclusion at the bottom of the page.
Surface air temperature
Here are the monthly temperature graphs for November-February in the Arctic Circle, from 2005/2006 to the past winter, based on the NCEP reanalysis dataset:
Last November saw the highest average monthly temperature in the 2005-2015 record, followed by a lower December, relatively speaking. Things then get a little bit crazy after the turn of the year, with the January 2014 record getting broken by almost 3 °C! February isn't far behind either, almost 1.5 °C higher than the already 'warm' February of 2014. This is unprecedented.
To see where temps were least low, I've created average temperature maps using the Daily mean composites page from NOAA's Earth Science Research Laboratory website, comparing the 2015/2016 freezing season to those preceding the years with the lowest minimums on record (click for a larger version):
The right hand corner of this overview really jumps out at you, doesn't it? The red blob of 5+ °C temperature anomalies that covers the entire Arctic Ocean during January is simply astounding. And again, February isn't far behind. Nothing comes close to it, really.
I found this image in the 2013/2014 Winter analysis blog post that shows what January and February 2014 - number 2 on the temperature graphs - looked like, a bit closer than other years, but still not that close:
Sea level pressure and ice drift
I've also created monthly average sea level pressure maps, as these tell us something about how cloudy the Arctic has been and which way the winds have been blowing, again compared to the freezing seasons preceding the years with the lowest minimums on record:
This year's SLP maps look quite similar to those of previous years, except perhaps for February which shows a bright, red dot of high pressure, indicating an active Beaufort Gyre which should cause ice transport through Fram Strait. This seems to be confirmed by this IFREMER/CERSAT sea ice drift map for February, with arrows clearly showing a textbook example of a strong Beaufort Gyre and Transpolar Drift Stream:
This movement caused another cracking event in the Beaufort Sea that I discussed in this blog post last month. We won't know what the effect of this cracking will be, as the 2013 cracking event seemed to reinforce the ice pack on the Pacific side of the Arctic, although it happened a couple of weeks earlier, during the height of winter.
Here's a glimpse of the cracking event, an AVHRR image provided by Environment Canada:
Speaking of radar images, here's the latest ASCAT image for day 86 (March 26th), compared to those of 2012, 2013 and last year:
Here's how these images should to be interpreted, according to the NSIDC:
The ASCAT sensor measures the radar–frequency reflection brightness of the sea ice at a few kilometers resolution. Sea ice radar reflectivity is sensitive to the roughness of the ice and the presence of saltwater droplets within newer ice (and, later in the season, the presence of surface melt). Thus older and more deformed multiyear ice appears white or light grey (more reflection), whereas younger, first-year ice looks dark grey and/or black.
There's definitely less bright white compared to last year, but overall things look slightly whiter than the situation preceding and following the 2012 record setting melting season. What sets this year apart from the other years, is a large patch of whitish ice on the Atlantic side of the Arctic. If that ice is indeed thicker, it could be poised to be transported through Fram Strait, depending on the winds.
Here are the AARI ice age maps for the end of March that show the amount of multi-year ice (MYI) in the Arctic (brown colour):
I'm surprised AARI is showing so little MYI in the Beaufort Sea towards the Chukchi, but the map for this year seems to confirm there's more MYI is surrounding the North Pole, almost entirely filling the entire 85-90N region.
Unfortunately, the well-known Tschudi/Maslanik/Fowler ice age maps that are used by the NSIDC for their reports are being overhauled, so I can't make any comparison. However, I did find some images running up to the first week of 2016, and I have to say they look very appealing visually (not that the old ones didn't). Here's the animation:
So, that ice on the Atlantic side of the Arctic seems to be second-year ice, in other words first-year ice that managed to survive last year's melting season. This makes sense as the ice pack there didn't have to suffer the double whammy of clear skies and high temperatures that it did on the Pacific side of the Arctic.
Ice volume and thickness
I have some more sources of info that give an idea of the current situation, as compared to previous years. Every month Wipneus makes interesting sea ice thickness distribution maps, based on PIOMAS data, which he posts in this Arctic Sea Ice Forum thread. These maps show the difference between the most recent monthly average and that of a previous year. Below is the difference between February 2016 and the same month in 2011, 2012, 2013 and 2015 (red means there's more ice now than then, blue means there's less ice now than then):
Just like the AARI ice age maps, these thickness comparison maps seem to imply that this year's ice on the Pacific side of the Arctic is thinner than it was in previous years, which may mean there is no barrier of thicker, older ice to protect the ice in the Central Arctic Basin. At the same time the ice is thicker on the Siberian side, according to PIOMAS.
It's good to remember that this is modelled data, not observations, and so we can't be sure about regional thickness. PIOMAS volume data for the Arctic as a whole, however, has been one of our best tools over the past years to assess conditions on the Arctic, and as I wrote a few weeks back in the March PIOMAS update, the increase in sea ice volume so far this year is the lowest on record:
The only direct observations of sea ice thickness we have, is provided by ESA's CryoSat-2 satellite. Although the archive is a bit of a mess, we still should be grateful that the Centre for Polar Observation and Modelling (University College of London) provides near real-time images. This data isn't perfect either, as it's very difficult to measure sea ice thickness, but below I compare thickness for the past 28 days to that of MarApr/Spring 2012 and 2013, and Apr9-May15 2015 (mind you, the ice will get slightly thicker as the volume max is reached mid-April):
These images also seem to confirm that the ice on the Pacific side is somewhat thinner than it was in previous years (more blue spots) and a significant part of the thicker ice is positioned right in front of the Fram Strait exit.
This analysis ends with an appraisal of Northern Hemisphere snow cover conditions, as these can also play a role in how a melting season develops.
Things didn't look all that great during February, but have improved somewhat recently as can be seen on this graph provided by NOAA STAR (Global Multisensor Automated Snow and Ice mapping system):
Here are the monthly anomaly maps from Rutgers Snow Lab for December, January and February:
Spring has come, light is slowly returning to the Arctic that has just experienced its warmest or least coldest winter on record. As suggested by the latest PIOMAS data, we have returned to similar initial sea ice conditions preceding the melting seasons of 2011 and 2012. This basically means that this melting season will get a shot at the record. It isn't a sure shot, of course, as there is no (direct) correlation between winter and summer sea ice conditions.
The Pacific side of the Arctic seems to be especially vulnerable this year, but maybe/hopefully the recent cracking event can help thicken the ice some more over there by letting the heat escape from the water (as presumably happened in 2013). At the same time, over on the Atlantic side of the Arctic, a lot of the second-year ice that survived last year's melting season is perfectly positioned for export through Fram Strait. And will the Northwest Passage and Northern Sea Route open up again, as they have done so many times in the past decade?
It's a cliché, but in the end the weather will determine this melting season's outcome. We'll now observe what changes occur during the transition time between winter and spring, until in a month or so that crucial first phase of the melting season starts, when melt ponds slowly start to form, which determines how much melting momentum is built up for the remainder of the melting season.