During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Because of issues with data based on the SSMIS sensor aboard DMSP satellites, I mainly focus on higher-resolution AMSR2 data from the Japan Aerospace Exploration Agency (JAXA), as reported on the Arctic Data archive System website. I also look at other things like regional sea ice area, compactness, temperature and weather forecasts, anything of particular interest.
September 10th 2016
It's that time of year when the melting season is drawing to a close and the Arctic sea ice pack is reaching its lowest size of the year, also known as the minimum.
This melting season was a strange one. After the mildest winter on record, a spectacular opening up of the Beaufort and Chukchi Seas made trend lines on graphs go extremely low even before the melting season had properly started. But then clouds moved in during the period when the Sun is at its peak, and solar radiation causes melt ponds to form on the ice pack, building up so-called melting momentum.
June and July were really cloudy, as cloudy as in rebound years 2013 and 2014, but this time around atmospheric conditions weren't accompanied by low temperatures on the ground and in the water. The warm winter, early opening up of the ice pack and the rapid melting of land snow cover, caused another kind of momentum, one of heat, that kept the melting going throughout.
And then in August, a massive storm that kept on re-intensifying (or maybe they were two separate storms), followed by a Dipole with a massive pressure gradient, battered the ice pack. Again, as in 2012, we've witnessed the detachment of one large piece of ice from the main pack. And now the 2016 melting season has reached 2nd place on almost all extent and area graphs out there.
You read it right, a melting season that saw mostly cloudy conditions during the sunniest period of the year (June-July-August) has beaten the 2007 melting season which went astonishingly low after weeks of ceaseless sunshine and a massive Beaufort Gyre, continuously compacting the ice pack, well into September.
But it looks rather unlikely that the 2016 melting season will end that late. The past few weeks have promoted massive ice dispersal, with large zones of low concentration near the Pole, and so there's a lot of compaction potential. But for compaction to happen, winds need to blow towards Greenland and the Canadian Arctic Archipelago, or else freezing temperatures start to dominate and all that open water within the ice pack and on its fringes starts to fill up with ice. The reverse is the case.
We can see that happen on this animation of Uni Bremen sea ice concentration maps of the past week:
The remnants of the now fully detached Wrangel Arm are still melting, compensating the ice growth elsewhere, but I'm pretty sure the minimum has been reached.
I will have a blog post with more images characterizing this melting season up later this week.
Sea ice extent (SIE)
These upticks in sea ice concentration are also visible on the latest JAXA SIE graph:
Wipneus is moving to a new place, and so his magical computer isn't on to provide us with the Cryosphere Today SIA replacement data, but my guess is that the minimum has been reached there as well, as the minimum usually occurs earlier on area graphs than on extent graphs.
Like I said, this daily minimum will probably be lowest on all graphs, but because it has occurred so early in the month and now moving up fast, the average September minimum - the metric used for the SIPN Sea Ice Outlooks - probably won't be 2nd lowest, as 2007 stayed really low all the way up to the end of the month. This has to do with weather, of course. High pressure kept compacting the already compact ice pack, whereas this year the ice pack was in a highly dispersed state due to the cyclones, and now that there is little compaction, below zero temperatures are taking over.
No compactness graphs either for this update, sorry.
Here's the animation of Danish Meteorological Institute SLP images showing the distribution of atmospheric pressure during the past two weeks:
You can clearly see at the start of the animation how big that Dipole was, but fortunately it didn't last all that long and conditions flipped. A weak cyclone took over the American side of the Arctic and that usually spells an early ending to the melting season. I wasn't sure if it would overcome all the heat in the water, but apparently it's doing just that.
One other sign that the melting season has ended, is when the trend line on the DMI 80N temperature graph starts shooting up, indicating that the water has started to release its heat to the atmosphere in order to freeze:
But it will probably go down a bit again, as a large part of the Arctic will continue to be cold this coming week (according to Climate Reanalyzer):
Expect that heat to come out soon, though, as SSTs are still anomalously high. Unfortunately I didn't archive the DMI SSTa images back in September 2012, as they would probably look similar to current images, but here's a comparison with SST anomalies in 2014 around this date:
It's quite amazing, really. If there had been just a few weeks of open skies when the Sun was high in the sky during June and July, I think the 2012 record low minimum would have been beaten. As it is, this melting season comes in second.
I always thought that it would take extreme weather conditions as seen in 2007 for a melting season to end really low: Lots of open skies, warm winds and continuous compaction, just weeks and weeks of the same kind of weather. But given that there's no let-up in the amount of heat flowing into the Arctic - via air and especially ocean - other set-ups can be just as destructive. It will probably be a back-and-forth of high pressure (open skies) and low pressure (dispersal, mixing) that will lead to new records, and eventually an ice-free Arctic.
That's the big lesson for this year. Things just aren't improving for the sea ice at all, and the fact that the cyclonic conditions we've seen this year, haven't prevent the second lowest minimum on record, doesn't bode well for the future at all.
Whatever it is we're doing to stop this from getting worse in decades to come, we need to do it faster.