I've waited an extra week with this post because I was on a holiday and because the minimum is about to get hit. More on that below, but first a short discussion of the PIOMAS August data.
Another month has passed and so here is the updated Arctic sea ice volume graph as calculated by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the Polar Science Center:
Just like last month, I had expected perhaps a larger drop. But whereas last month the volume loss was still above average, this month's isn't. The 2007-2017 average volume decrease for August is 2578 km3, and this year it was 2347 km3, more than 200 km3 lower. This means that 2018 is back in 6th position again, as the difference with lower years (except last year) has grown again.
Here's how the differences with previous years have evolved from last month:
On Wipneus' version of the PIOMAS graph we can see how the trend line made a slight drop towards the end of the month, veering away from 2013:
On the PIOMAS volume anomaly graph, the anomaly trend line has crossed the linear trend line again, and it might very well stay there until next year:
As for average thickness (crudely calculated by dividing PIOMAS volume with JAXA sea ice extent numbers), the trend line continued to flatline, as is usual for this time of year, but here too we see a small drop towards the end of the month:
Not much different on the Polar Science Centre thickness graph:
Now, the main reason volume didn't drop as much as I expected (not just last month, but perhaps the entire melting season), is that the regions where PIOMAS showed thicker ice since at least the start of the melting season, on the Siberian side of the Arctic mainly, didn't melt out completely. As I wrote last month, the situation in the Eastern Siberian Sea was going to be crucial for the position this year's melting season will end at. If we compare the situation at the end of August with the same date in 2012, 2016 and 2017, for instance, we'll see that the red is where the big difference lies (red means thicker now than back then, blue the reverse):
As we've seen before throughout the years, some ice will stubbornly refuse to melt out completely, no matter how fragile and vulnerable it looks:
And it's not just the dispersed ice in the big red circle, but also the ice in the other two red circles that tells the tale of this melting season. On the Atlantic side of the Arctic, the ice edge has retreated North like we haven't seen before for a comparison (see here), especially if you consider the fact that the Greenland Sea is practically ice-free. This has been due to the fact that there has hardly been any transport of ice through Fram Strait, which in turn means there has been almost zero movement towards the Atlantic, and this means that there was very little, consistent high pressure over the region of which the Beaufort Sea could be considered the centre.
For this very same reason there has been relatively little action on the Pacific side of the Arctic this year. Combine that with not too spectacular surface air and sea surface temperatures, lingering land snow, not enough preconditioning to build up serious melting momentum, and somewhat thicker ice on the Pacific/ESS side due to the freezing season, and it's only logical that the 2018 minimum will end up outside of the top 5 for most datasets. Still low, but not as low as we've seen a couple of times this past decade.
So, even though 2018 has been a somewhat boring melting season (though the unprecedented retreat off of Greenland a few weeks ago was quite a treat), there is one last exciting thing that may keep me up tonight. On the ASIF poll for the JAXA SIE minimum I voted '4.0-4.5 million km2', and according to the latest data it's 4.514 million km2:
And it could happen, given the current weather forecast, with a massive high pressure system staying put over the Beaufort Sea for another 4-5 days:
Maybe peripheral refreeze can offset late melt and compaction to the point that the minimum has already be reached, but I think it will take a few more days. It's safe to call it next week. Here's how things look, compared to previous years (hat-tip to Hautbois):
And so we've seen three extremely mild winters in a row, with record low volume and sea ice extent/area maximums, but no follow-up during summer. Maybe there's a pattern there, some negative feedback...