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.
June 29th 2016
The run-up to this melting season was really special, with an unprecedentedly warm winter season and early opening of the Beaufort Sea. Sea ice extent and area numbers went extremely low for the time of year, and sea ice volume reached the depths it was at before the 2013-2015 post-record rebound. But events in the Arctic don't behave like a straight arrow. Not in the short term, at least.
Weather conditions switched around the start of this month (see previous update) and prevented a large-scale soaking up of solar radiation through leads and melt ponds that would've increased the chances of a new record low September minimum even more. The lack of melting momentum has in fact decreased the chances to the point that I'd bet against it. If you want more details, read these two posts, or this blog post by Chris Reynolds that is hot off the press.
Mind you, this is not a melting season like 2013 or 2014 where persistent cloudiness and low temperatures caused relatively high September minimums (compared to top 3 years like 2007, 2011 and 2012, of course; they were well below the long-term average). 2016 still has many aspects going for it, like all that open water in the Beaufort Sea, low volume and snow cover that vanished at record speed. But it will take more to beat 2012, or 2007 and 2011 for that matter.
So, that's the question I will focus on in weeks to come: Can 2016 still make the top 3?
Sea ice extent (SIE)
2016 is no longer number 1 on the JAXA SIE graph:2016 went lowest on March 28th and stayed lowest all through April and May, a full three months. This tells us something about how amazing the melting season has been so far. But after a low daily average of just 48K this month (2010 and 2012 had 77K and 78K respectively) and zero century breaks so far, the trend line has re-joined the pack.
By dividing sea ice area numbers with sea ice extent numbers we get an idea of how compact the ice pack is. Are the ice floes huddled together, or is the ice pack riddled with leads and melt ponds? The lower the percentage is, the more 'holes' there are within the pack (for a more thorough explanation on compactness read the Melting momentum part 2 blog post).
I use Cryosphere Today sea ice area data (as calculated by Wipneus over on the forum) and divide them by JAXA SIE data, resulting in the CAJAX graph:
2016 is smack in the middle of the pack of trend lines, indicating this is an average melting season (for now).
No regional graphs in this update. I'll be using them for a separate blog post to keep this one shorter.
Here's the animation of Danish Meteorological Institute SLP images showing the distribution of atmospheric pressure during the past two weeks:
Blue and green, representing low pressure, have been dominating the Arctic. For a very short period 973 hPa was reached last week, which is quite low, but the cyclone was too short-lived to do any real damage (like we saw in August 2012). This low pressure dominance is the sole reason that extent decrease has slowed down and melting momentum is (below) average. It isn't very low though and has dispersed the ice pack somewhat, which may play a role later on.
If you want extent to go down fast, you want open skies and compacting winds, in other words high pressure, preferably somewhere between the Central Arctic and the American coast. Let's see if the ECMWF weather forecast model has any of that in store for the coming 6 days (click for a larger version, and go to the ASIG Forecasts page for daily forecasts):
Low pressure remains dominant over the Central Arctic, but high pressure is getting a firmer grip on the American side of the Arctic. This set-up may not be ideal for rapid decreases in sea ice extent, but could have quite a negative effect on the thicker ice in the Canadian Arctic Archipelago (Northwest Passage central route opening up?) and Beaufort Sea where the multi-year ice floes are in a rout.
Unlike the first few months of this year and the start of melting season, temperatures haven't been out of the ordinary during the past few weeks, just slightly above average. Here's an animation showing the GFS weather model temperature anomaly forecast maps for the coming week, as provided by Climate Reanalyzer:
There is one more trick up 2016's sleeve I forgot to mention though, and that's sea surface temperatures. Below you can see current SST anomalies in the Arctic, according to DMI, followed by a comparison to the situation on July 1st 2012, June 28th 2014 and July 7th 2015:
This year is looking almost as hot as 2012 - much hotter near the North Pacific - with a few more days to go until July 1st. Comparable too to 2015, but hotter in the North Atlantic, with more than a week left to go until July 7th.
This is another aspect that speaks in favour of 2016 still going low this year. But SSTs alone won't suffice.
It's difficult to assess where 2016 stands exactly at the moment. Conventional wisdom will say that current weather conditions and lack of melting momentum are precluding a new record low September minimum, and I tend to agree, based on what I have learned over the past few years. I expect 2016 to be overtaken by 2012 on the JAXA SIE graph in the coming two weeks, and then when August comes 2012 will be out of reach.
However, Arctic sea ice wouldn't be such an interesting phenomenon to watch if it didn't behave as unexpected as it often does. As said, certain aspects of this melting season suggest more could be going on than meets the eye. But it will take a July like last year (see here), with plenty of open skies and record high temperatures, for this year to go really low and end up in the top 3. 2015 almost managed to do that, despite a relatively high amount of volume at the start of the melting season and a serious lack of melting momentum during May and June.
It's crunch time, but no signs of open skies and high temps as of yet.