The regional PIOMAS Data and Thickness Plots that I produce are now updated. See the top right panel on the blog for links.
In my last update on PIOMAS I showed how despite 2014 having a spring melt, the spring melt had been curtailed. This suggested that volume by the end of July would be high because after each spring melt anomalies rise.
However the rise of anomalies has been rapid this July (more so than I had expected), implying seriously below average losses of volume, this may continue into August and the final August volume figure may show an even greater August volume when compared to other years in August. Failure of melt against a climatological background of melt could result in a surprisingly high minimum volume at minimum, even give the surprise of July's volume. No, I am not making any guesses, at this stage I'll just wait to see what happens.
The above plot of regional volume shows that in the PIOMAS model the volume increase has been limited to the Central Arctic region, it is hard to make a case for increased volume in other regions. Notably the Central Arctic volume is now back to levels last seen in 2009, before the volume loss of 2010. Taking the gain of volume from 2012, most of this is accounted for by the increased volume in the Central region.
Turning to average thickness for the regions of the Arctic Ocean, from Beaufort through to Kara, and Greenland, thickness is only of the same order as the post 2007, or post 2010 average. Barents is above average for recent periods but the extent in Barents is low and this accounts for very little of the overall volume increase. It is in the largest region in the sense of both volume and extent, Central Arctic, that we see a marked increase in thickness, the Canadian Arctic Archipelago (CAA) also contributes to this.
It is worth pointing out that Central Arctic thickness in July 2014 is 2.051m, in July 2009 it was 2.052m, the law of large numbers (or large sets of numbers) continues to amuse.
Looking at map-plots of thickness July 2014 is seen to be more similar to July 2009, than to July 2011 (for example).
However note that the thickness outside the Central Arctic was higher in 2009 than in July of this year. Note also - those are plots of thickness down to zero, so even tiny grid box thicknesses implying dispersed ice are included in the plots above, hence the unrealistic ice edge.
Before I move on to the regions, what has really surprised me is in the rate of change of PIOMAS volume, which I calculate in ten day increments.
The changes for 2014 are shown in red, note that the decline from the 1 July to 10 July is virtually the same as the decline in volume for the period 11 July to 20 July, when the overall shape of the curve suggests that typically the earlier period should show a greater decline in volume than the later. It looks like something was happening in early July that seriously reduced the volume loss one would expect for that period. At that time high pressure dominated and temperatures were about average for the 1981 to 2010 baseline used by NCEP/NCAR, in other words, cold for recent years.
Now for the regional breakdown.
Whole PIOMAS Domain.
Volumes in ice from grid boxes with thickness of 0 to 2.9m shows little change from previous years, the longer term patterns of change are preserved in such ice. However the same pattern seen in Central Arctic volume in the first graph of this post is repeated here in the 3 to 3.9m thick band. Volume from the thickest ice, >4m thick, has risen slightly but remains very low in the long term context.
The progressive change of volume/thickness profiles shows the sort of collapse typically expected in July, however in comparison to other post 2010 years (see below) there is a lot of volume above 2.7m thick that does not decline significantly as the melt season passes.
Comparing July 2014 with other post 2010 years shows a similar distribution below around 1.6m thick, with an increasingly unusual amount of volume for thicker ice.
In Beaufort the PIOMAS data shows that conditions are fairly typical for recent years. Certainly this is not like July 2013 in Beaufort.
The progression of melt is normal from April to July, as is to be expected for July the mono-modal peaks of first year ice in April, May and June collapse as thinning occurs at different rates smearing the distribution of volume with thickness.
Comparing thickness distributions with other post 2010 years reveals that 2013 was very different to the other years and that in Beaufort PIOMAS finds conditions relatively normal for recent years.
East Siberian Sea (ESS).
Once again the ESS shows no indication of increased volume or thicker ice. Volume in the 1 to 1.9m band is similar to recent years while volume in the 0 to 0.9m band continues to increase as summer ice thins.
The progression of thinning in the ESS - normal, yada yada. ;)
Thickness distribution normal compared to recent years, no big slug of thick ice.
However at this point it is worth noting that PIOMAS doesn't explicitly model first year and multi year ice categories. I still think there is multi year ice in Beaufort, Chukchi and the ESS, I still think that will delay melt. It's just that PIOMAS doesn't pick it up and models ice properties based on the effect of thermodynamic and mechanical growth of thickness on the thickness distribution.
While the rest of the Arctic Ocean is fairly normal for recent years the Central region is not. Ice thickness of 1 to 1.9m and 2m to 2.9 continue to mirror each other, when ice is thinner it falls in to the former band, when thicker it falls into the latter band, and as ice moves between the two bands their progression of volume mirrors each other. This year more thinner ice volume is thicker and has fallen into the 2m to 2.9m band.
Looking at ice of 3 to 3.9m thick, once again we see the 'bucket' of 2010 to 2013, delineated by higher volume in 2009 and 2014. Note that the 'bucket' in the Central region is about 2k km^3 deep, similar to the depth of the 'bucket' in the 3 to 3.9m ice of the first graph of the 'Whole PIOMAS Domain' section above.
Taking the overall volume difference between July 2012 and July 2014, in the Central Arctic the overall volume difference between those two months is 2.072k km^3, for the Arctic Ocean the overall volume difference is 2.633k km^3. Therefore the Central Arctic accounts for 79% of the volume increase since July 2012 for the whole Arctic. Of the 2.072k km^3 increase between July 2012 and July 2014 in the Central Arctic, 88% is from ice between 3 and 3.9m thick. Taking the Central Arctic's balance of 79% of the total gain in volume between July 2012 and 2014, Central Arctic ice between 3 and 3.9m thick accounts for 70% of the total volume increase between those two years. The volume increase is not only confined to a specific region, but within that region it is confined to a specific thickness band.
The July collapse of thickness profile is never as marked in the Central region as in the peripheral seas of the Arctic Ocean, however this month it is clear that a large amount of thicker ice holds volume up.
This is even more clear comparing July 2014 to the other post 2010 years, above 3m the difference is striking.
The cool weather and poor melt seasons of 2013 an 2014 have put us back to pre 2010 total volume. However it is far from clear that the overall state of the pack has reverted to pre-2009.
This does present a nuisance to me. I recently posted that I had changed my mind and that for specific reasons unrelated to this increase in volume I now expect a seasonally sea ice free state not to occur until later in the 2020s, possibly later. The events of this year and the last make no difference to that expectation. But it looks like I will have to wait several more years before I can again start counting down the years that April volume floors at the level I expect. However another way to look at it is this: We've seen volume around 19k km^3 (that which would be expected for a mostly FYI pack) from April 2011 to 2014, if this volume pulse takes several years to work through the system and then we see a new levelling of April volume to around 19k km^3, with the intervening disturbance it should be a strong indicator that we don't face a fast crash, but that we face a slow transition.