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:
Volume increases for December in the last 10 years aren't all that far apart, ranging from 3500 to 4000 km3 (rounded off). This year was on the lower side of that range, with 3547 km3. Only 2010 and 2014 were lower than that, just barely. This means that 2017 ends the year in third spot. The gap with 2012 has been reduced some more, from 733 to 497 km3, and the quickly widening gap with 2016 has stopped widening for now, going from 1482 to 1340 km3.
Here's how the differences with previous years have evolved from last month:
On Wipneus' version of the PIOMAS graph you can see how that difference with 2012 has become smaller again since September (red is 2017, purple is 2012):
And the trend line on the PIOMAS sea ice volume anomaly graph climbs up some more into the positive standard deviation territory:
As for average thickness (crudely calculated by dividing PIOMAS numbers with JAXA sea ice extent numbers), 2017 has ended the year in 4th position, with 2011 edging past in the final week of the year:
The same goes for the thickness graph from the Polar Science Centre:
So much for PIOMAS, which is a model. But there's also a satellite up there in the sky, called CryoSat-2, with a sensor on it that provides sea ice thickness observations. And this month Stefan Hendricks of the Alfred Wegener Institute was so kind as to tweet some information regarding the December numbers:
The tweet was accompanied by a map and a couple of graphs, which are reproduced below. The first graph shows this December had the third lowest volume gain since 2010. The middle graph shows growth for OND (October, November, December) with trend lines and ranking numbers for total volume at the end of each respective month, and just below that are blue bars showing total winter cumulative gains for previous years, and this year so far (at 3 million km3). The lowest graph shows winter cumulative gain for all years for OND, with this year clearly being lowest:
All of this isn't surprising, of course, as JAXA sea ice extent finished the year lowest on record, for the first time staying under 12 million km2:
This is also reflected in air temperatures. The Arctic is experiencing another mild winter so far. As the NSIDC's latest monthly summary has it:
December air temperatures at the 925 hPa level (about 2,500 feet above sea level) throughout the Arctic Ocean were 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) above average. Prominent warm spots were found over north Central Asia and Central Alaska (more than 10 degrees Celsius, or 18 degrees Fahrenheit above average), as well as over Svalbard and Central Siberia (nearly 6 degrees Celsius or 11 degrees Fahrenheit above average). Temperatures were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) below average in Eastern Siberia.
I borrowed their temperature map and combined it with my NCEP reanalysis temperature graph (courtesy of ESRL, Physical Sciences Division). December 2017 is least coldest on record by far. Below it are temperatures from the four Arctic quadrants, and the Pacific is clearly contributing most of the mild temperatures, while Siberian and Canadian are also up from last year (click for a larger version):
Last year the heat came in through the Atlantic, bringing with it snow that fooled CryoSat into 'thinking' that the ice was thicker than it actually was. That snow, both on land and the ice, eventually slowed down the first stage of melting (or preconditioning of the ice pack via melt ponds) enough to prevent records from being broken further than they had already been up to that point. This year the heat is being supplied from the Pacific side of the Arctic, but I'm not sure whether it's being accompanied by vast amounts of snow again. Maybe CryoSat would have picked it up, like it did last year.
Either way, on land, snow extent has been slow to grow this year, showing another lowest on record for this time of year (total Northern Hemisphere on top, Eurasia below, from NOAA's multisensor snow cover maps):
This is mainly caused by a lack of snow in Eastern Europe according to Rutgers University Global Snow Lab, so no need to speculate about possible effects for the upcoming melting season, as of yet:
Finally, to return to PIOMAS. Here's a graph showing volume export through Fram Strait into the North Atlantic, according to the Polar Science Centre's model (courtesy of the prolific Wipneus on the Arctic Sea Ice Forum). As you can see things were amazingly slow during the 2017 melting season, but things have picked up again in recent weeks:
So, that's it for now. Another winter where things aren't looking so great for the Arctic, with records being broken all around. Still, we're only halfway through the winter, so maybe there's still some cold to come. And as we've seen the past two melting seasons a mild winter doesn't necessarily make a record summer a done deal. Hope dies last.