Wednesday, 5 July 2017

Arctic sea ice update - 04/04/2017

An update from Neven Curlin of Sea Ice Blog


PIOMAS July 2017



4 July, 2017

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:

BPIOMASIceVolumeAnomalyCurrentV2.1_CY
Last month we finally received some good news from PIOMAS, and the good news continues this month. With 2017 losing a below average amount of sea ice volume during June (compared to the average of the last 10 years), while a couple of years losing a great deal of volume, such as 2010, 2011 and of course, record smasher 2012, the gap has effectively been closed. At the end of May the difference between 2012 and 2017 was 1481 km3 (a month earlier it was 2412 km3 even), and now it's just 131 km3.
Here's how the differences with previous years have evolved from last month:
Change monthly difference June 2017
And here's Wipneus' version of the PIOMAS graph that shows even more clearly how large the gap has been since the start of the year, with the 2017 trend line now finally converging with its followers:
Piomas-trnd4
And although the trend line on the PIOMAS sea ice volume anomaly graph is still extremely low, at least it hasn't completely crashed to the point where it leaves two standard deviation territory (it probably will next month):
BPIOMASIceVolumeAnomalyCurrentV2.1
So, things look a lot better than they have for quite some time, but of course, that doesn't mean it's good. The weather hasn't been extremely conducive to melting so far, but it's no 2013 or 2014 either, where clouds and low temperatures saved the Arctic from falling in the hole that 2012 had left behind. This relative slowdown in melting is probably caused by the excess snow that has kept the thin ice white enough for melt pond formation to come later than it otherwise would have (as described in this bonus blog post on melting momentum I wrote a few weeks back).
The question now is whether this will be enough to keep 2017 from a reaching a new record low sea ice volume come September. Of course, only weather can prevent this from happening, and it will probably take some cold and cloudy weather. But only if the current trend follows the 2014 scenario, can a new record be avoided, as visualised by this Jim Pettit graph, showing all possible trajectories based on historic data:
Siv_projections_from_current_date
As Jim says in the PIOMAS thread on the Arctic Sea Ice Forum: The averageJuly-through-minimum melt of the last ten seasons would render a 2017 September minimum of 3.18 thousand km3, or nearly 500 km3 below the 2012 record.
This same thread has various graphs and maps on display, such as a comparison map in which PIOMAS data wizard extraordinaire Wipneus compares where this year the ice is either thicker (red) or thinner (blue) compared to a particular year. I've taken out 2010, 2011 and 2012:
Comparison June 2017 vs 2010-2011-2012 V2
As I wrote myself on the PIOMAS thread:
Very interesting to have the gap with 2012 close, but at the same time see this huge discrepancy, an almost diametrical opposition, on the comparison map. Sure, 2012 will catch up with the dark blue in the Chukchi and ESS where the ice has disappeared quickly this year, but the same goes for 2017 with all that red on the Atlantic side, especially that big blotch north of Svalbard and of course Baffin Bay. And then there's that last zone of red, in the CAA, that has received plenty of sunshine during the past few weeks.
It implies that it should be more than possible for 2017 to keep pace with 2012.
So, if the snow no longer plays such a big role, as satellite images and theNSIDC compactness graph seem to suggest, and weather and sea surface temperatures remain around average, 2017 will end up at least second lowest on record for sea ice volume (and if it does, other metrics will follow).
We'll know more next month, keeping in mind that 2012 didn't repeat June's volume scorcher, meaning the gap could possibly widen again.
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Only now do I notice that I had forgotten to post the average thickness graphs. Here's my PIJAMAS graph (a crude calculation of PIOMAS volume numbers divided by total JAXA sea ice extent), followed by the Polar Science Center thickness plot:
PIJAMAS20170630
Bpiomas_plot_daily_heff.2sst




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