In the last week CT Area anomalies have shown two substantial drops, followed by a suggestion of a downward slope. The prediction I previously made, link, is shown in dark blue, it lies between the central and lower bounds. Following the early August storm of 2012 CT Area anomalies fell throughout August, it had seemed that this year the gap between 2012 and 2013 would widen due to 2012 moving ahead with a higher August loss rate, however this may not be the case, we could see exceptional losses in August this year.
The US Navy's HYCOM sea ice modelling system suggests things may just be about to get very interesting.
There is a reduction of thickness in Beaufort, lower left quadrant, this was caused by a strong low pressure system. However it also seems to lead to a rapid drop of thickness in Chukchi and the East Siberian Sea (upper left quadrant).
This low pressure system has driven strong ice movement in the Alaskan sector.
The low pressure system itself is seen on the plot below. It's the third of three successive cyclones in the same region, eg Neven's Blog, but this seems to be the one that will have impact, if HYCOM is correct.
For context it's worth looking at what HYCOM shows for past years on the current date.
The pack as modelled in HYCOM is shown to be in a far poorer state than the other available years. PIOMAS shows that by August volume losses are far below their peak in early July, but with ice as thin as HYCOM suggests it won't take much volume loss to reveal a lot of open water.
The following table is of July CT Area losses so far, in million km^2:
| 1992 | -2.92954 |
| 1987 | -2.92471 |
| 2013 | -2.87922 |
| 2009 | -2.83418 |
| 1985 | -2.72614 |
| 2007 | -2.68295 |
| 1981 | -2.64814 |
| 2002 | -2.63538 |
| 2011 | -2.62251 |
| 1990 | -2.57034 |
2013 is in the top three losses and well ahead of 2012 for July loss, 2012 is at 24th place with a loss of -2.36M km^2. If HYCOM is getting it right at present than we could see 2013 make a good running, if not for a new record, for a solid second place.
With regards my prediction method of early this month, the question now becomes how big a sigma deviation this year will be. Will the lack of trend of CT Area losses from 20 June to minimum reveal 2013 to be a black swan year? And given that 2013's atmospheric set up has not been as conducive to ice melt as the strong dipole anomaly patterns of 2007 to 2012, is the only interpretation that the ice really is on the threshold of an exciting crash. Is the ice critically thin and does 2013 show this despite the weird* weather this year?
*weird in the context of the other post 2007 years, link.
3 comments:
Go to IARC-JAXA and look at the "RGB(36V,36H,18V)" map for today. The ice looks like Swiss cheese in the Alaska sector up to 80N or so. I don't expect it to make it past mid-August.
Much of the rest of the pack has been low-concentration < 75% on CT since the 17th of this month, if not before. I expect it to be gone this year too, though it may make it to the end of August.
Chris,
I've thought for some weeks now that the race would begin on or around August 1st; that's when I thought 2013 would catch up to 2012. But I'm less confident now than I have been anytime this season that 2013 *will* actually pass 2012.
I agree that qualitatively the ice-pack overall is in worse shape, I'm just not sure if that will show up in the final SIE or SIA numbers. What I'd really like to see are comparable ocean temperatures for the Marginal Ice Zones. This might help tell us if the melt season will extend longer and/or if refreeze will take longer to kick in.
The decimation of the Beaufort/CAA MYI first began showing up on HYCOM Thickness & Concentration projections run on the 19th or 20th and became more noticeable with each passing day. If this leads to SIE losses this season then a new record could yet be set. Otherwise we'll have another 'recovery' where the ice is worse off than the year before continuing the downward spiral by preconditioning it for the 2014 melt season. Either way it's just a continuation of the 'Bye, Bye Arctic Sea-Ice' story.
Nightvid,
I've got no experience of handling and reading those plots, so I stick to Bremen visual plots. Those show a lot of low concentration out there.
Kevin,
I'm not totally convinced that we'll beat 2011 and begin to approach 2012 (CT Area). But it now seems like there is a realistic prospect of unusually large losses in the coming weeks, which opens up that possibility.
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