Another late update. Apologies. It must be because winter is a-coming.
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:
The October sea ice volume increase of 2592 km3, according to the PIOMAS model, was pretty much run of the mill. However, two years in the past decade do not fit that bill/mill, as they showed very muted growth during October: 2007 (1637 km3) and, of course, last year with 1648 km3 (things would get even crazier during November). 2017 is still fourth lowest on record, but the difference with 2012, 2016 and 2011 has grown and 2017 is now practically on a par with 2010.
Here's how the differences with previous years have evolved from last month:
And here's Wipneus' version of the PIOMAS graph (including 2007):
And as I suspected last month, trend line broke through the linear trend (straight blue line) and has entered positive standard deviation territory:
And here are the average thickness maps. The first is made by me and is a crude calculation of PIOMAS volume numbers divided by total JAXA sea ice extent, the second is from the the Polar Science Center itself. The 2017 trend line has shot up a bit and is now on a par with 2016:
To close off, I'd like to share two more images related to air temperatures in the Arctic. Here's a graph I made using NCEP reanalysis data (provided by ESRL) that shows air temperature at the 925 hPa level during October since 2005. This past October wasn't quite as 'less cold' as last year's, but still second highest on record:
The other comes from commenter Tealight's CryosphereComputing website and shows the cumulative FDD (freezing degree days) anomaly since the start of the freezing season. Here too this year is second after 2016:
And one more bonus from the PIOMAS team at the University of Washington Polar Science Center, showing how PIOMAS model data and CryoSat-2 observational data are tracking relative to each other. During the previous freezing season there was a large discrepancy that developed around this time, with PIOMAS showing the trend line going down steeply compared to the previous year, while CryoSat-2 showed the trend going up (see this graph and the PIOMAS March update blog post for an explanation). It turned out that this told us something about the amount of snow on the ice pack, as CryoSat-2 has difficulties separating the two (hence the volume trend line going up), and this probably had a large influence at the start of the melting season, when melt ponding preconditions the ice pack for the remainder of the melting season.
So far, both trend lines are tracking in the same direction:
That's it for the time being. We now await next month's data, and I'll make sure to post the update on time next month.