PIOMAS data came in a bit later this month, and I'm a bit later still, but this gives us an opportunity to look at what may happen during the second half of the month.
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:
Given the heat on the Siberian side of the Arctic and extensive melting in the Kara and Laptev Seas I had expected a larger drop. Nevertheless, a loss of 6229 km3 of sea ice volume is well above the 2007-2017 average of 6020 km3. This essentially means that 2018 has caught up some more with the years in front of it, and even slipped below 2016 (the difference is a mere 17 km3), which means it's in 5th position as of July 31. The difference with 2012 has been reduced with 610 km3, and is now 907 km3.
Here's how the differences with previous years have evolved from last month:
And here's Wipneus' visual representation of the PIOMAS data. If you look closely you'll see the 2018 trend line veer off slightly to the right, and that's where I expected it would continue to go down:
Something funny has happened on the PIJAMAS graph, showing average thickness for the entire Arctic ocean (a crude calculation where you divide PIOMAS volume with JAXA extent). It seems that extent has gone down relatively faster than volume, and so the average thickness has flatlined instead of going down. Basically, it means that more volume is spread over a smaller expansion of sea ice. This too, perhaps, explains why I expected volume to have gone down more during July. I expected volume to follow extent, and thus thickness to continue to go down some more:
We see the exact same thing happening on the Polar Science Centre thickness graph:
I'm convinced this has everything to do with the sea ice in the East Siberian Sea. This is where the big difference with other years originates, according to PIOMAS, as can be seen on these comparison maps that Wipneus posts every month on the PIOMAS thread on the Arctic Sea Ice Forum (red means thicker now than back then, blue the opposite):
When that ice melts out, I expect 2018 to creep some closer to the 4-5 years that are lower right now. The average drop for August in the 2007-2017 period is 2578 km3. 2018 should be able to top that this month. Because here's how the ice in the ESS is looking right now (source: NASA EOSDIS Worldview):
The ice in the East Siberian Sea has been subjected to some late heat and sunshine, and right now some warm southerly winds are blowing over it, projected to continue for two more days, which should significantly melt/compact it. At least that's what the ECMWF weather model is forecasting (images from Tropical Tidbits):
It looks like a high pressure area will move in again over this vulnerable zone after D3, which might disperse the ice again, but at the same time subject it to some very late sunshine. Either way, this will in a large part determine the outcome of this melting season, because, together with the Central Arctic Basin, the East Siberian Sea is where the most can be gained/lost, as Wipneus' regional AMSR2 sea ice area graphs show:
I've added the CAB graph to show that 2018 almost certainly won't be able to keep up with 2012. If there's a cliff of sea ice loss in the ESS, and the 2018 trend line can somewhat keep up with 2016 on the CAB graph, this year's minimum may end up in or close to the top 3. Personally, I think it will be a top 5 position. But this, as always, will also depend on the weather.
This excellent visualisation by commenter Hautbois shows the final stretch: