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.
July 20th 2016
Three weeks have passed since the previous ASI update, but I must say that I haven't become much wiser since then. I was expecting this year to start falling behind on the extent and area graphs, as weather conditions that aren't really conducive to melting, have continued to dominate the Arctic.
More than one month and a half of cloudy weather, not exceptional warm, little compaction, hardly any Fram Strait export, but this year somehow still manages to stay among the lowest on record. Such circumstances would have inevitably led to a major stalling on the graphs in previous years, but not this year. It would seem the lack of melting momentum is being compensated by another kind of momentum, brought on by the mild winter, early melt onset/opening up, extreme low snow cover and anomalously high sea surface temperatures.
The question still is whether this year has the oomph to end up in the top 3 September minimums, but whereas three weeks ago I thought it probably wouldn't, I'm not so sure anymore.
Which is strange in a way because the 2016 trend line on the JAXA SIE graph - based on data provided by ADS-NIPR - has slowed down to the point that 2016 is now in third position:
But given weather in the past two weeks I had expected it to be somewhere between 2014 and 2010. If it now somehow manages to end the month between 2011 and 2015, there's still room for August weather to keep the race exciting.
In the meantime 2016 is still second lowest on the Cryosphere Today sea ice area graph. CT hasn't updated their data since the SSMIS satellite sensor abord the DSMP F17 satellite started relaying faulty measurements, but over on the Forum Wipneus keeps calculating what the numbers would be, based on his reverse engineering of CT's method to calculate SIA:
It makes sense that area is lower than extent, because there has hardly been any compaction in the past few weeks. The ice pack has been spread out by a couple of cyclones too, as can be seen on the latest satellite images. The effect is clear on compactness graphs as well (for a more thorough explanation on what compactness is, read the Melting momentum part 2 blog post).
Here's the CAMAS compactness graph (CT SIA divided by MASIE) as interannual differences are more distinct:
2016 was lowest for a while, but has shot up somewhat. On Wipneus' compactness graph, based Uni Hamburg's AMSR2 data with the highest resolution (3.125 km), this year is lowest by a large margin after a steep drop (original here):
Here's the animation of Danish Meteorological Institute SLP images showing the distribution of atmospheric pressure during the past two weeks:
The animation starts and ends with a cyclone, a continuation of the story since the start of June. Both cyclones were of reasonable strength, but not very long-lasting. Enough to stir up the ice pack, though.
As the compactness graphs showed, there is quite a bit of compaction potential, and the Sun is still high up enough to assist bottom melting and hurt the ice pack some more. But this requires sunny skies, and thus high pressure areas. Here's what the ECMWF weather forecast model has in store for the coming 6 days (click for a larger version, and go to the ASIG Forecasts page for daily forecasts):
There will be clear skies for another day or two over the East Siberian and Laptev Seas where the supposedly thicker ice is lingering longer than we've become accustomed in the past decade. After that high pressure gets squeezed by low pressure on both sides, not becoming intense and dominant enough to increase compaction and Fram export.
As for air temperatures, the Atlantic side remains anomalously warm, but colder temperatures take over all around the Arctic coasts, according to the GFS weather model temperature anomaly forecast maps for the coming week (provided by Climate Reanalyzer):
So, it's all up to sea surface temperatures to keep the train moving. Here's how yesterday's DMI SST anomaly map compares to those of July 28th 2012 and July 29th 2015:
2016 looks slightly hotter than 2015, and not that much behind 2012 either. Mind you, there's still 9-10 days to go before we can make a one-on-one comparison.
I've always said that as soon 2007 weather conditions happen again during a future melting season, records will be broken and the Arctic might even go ice-free. During the summer of 2007 persistent high pressure led to sunny skies, increased Fram export, and lots of compaction.
This year's lessons have changed the way I think about this. Compaction may cause extent to go very low, but at the same time a lot of ice is pushed together towards higher latitudes, which makes it much harder melt. The first year of ice-free conditions will inevitably entail some dispersal as well.
All it takes, is relatively thin ice after a mild winter and early melt onset (similar to what we saw this year), followed by clear skies and high temperatures during May and June to get that melting momentum going. Then a bit of high-pressure-low-pressure ping-pong during July, followed by a big cyclone during August, et voilà: ice-free conditions. The question is not if, but when all these conditions will line up.
In the meantime, we wait to see if 2016 can stay close to the top 3 years. This may very well be decided in the coming period. A breaking point.