I've been increasingly quiet on this blog over the back end of last month, I must admit I've been finding it hard to be bothered to post, other interests have been taking precedent. Anyway, as I feel compelled, here is a quick last blog of of the summer.
2015 daily minimum extent looks likely to be the second or third lowest on record, not bad after two years when we have been assured by some that the Arctic sea ice is recovering.
And zooming in to the minimum, it is clear why 2015 may be the third lowest daily extent. If the current levelling persists it will be third place, but a further drop may still happen.
And what of PIOMAS volume?
The volume increase of the last few years persists, is still restricted to the Central Arctic.
June was average melt weather but July saw a very strong Arctic Dipole and strong losses off Siberia, overall this compounded low compactness leading to strong losses through August. This is seen in the August extent losses.
Using anomalies with a baseline of 1981 to 2010 during the period of the Arctic Dipole above average losses were seen in the East Siberian Sea and Laptev Sea (red). Once this lead had been established it persisted through the summer. But this set up conditions for above average losses to start in the Central Arctic and Canadian Arctic Archipelago (where the Arctic Dipole was less of a factor).
The pattern of losses from outside the Central Arctic opening that region up for encroachment of the ice edge is a relatively recent development since 2007. Looking at a seven day average of extent centred on 31 August the Central Arctic (blue) remains resilient to extent losses outside that region, until 2007.
Using the same 7 day average centred on 31 August it is possible to see the behaviour close enough to the minimum to reflect the behaviour of the daily minimum extent (without needing to wait for the actual 2015 minimum!)
There is a clear downward trend. However what happens after 2007? Now in 2015 we have 9 years of data, which is heading towards a dataset worth saying something about, and allows us to make some tentative suggestions about the emerging nature of the post 2007 environment.
As of 2012 one would reasonably have concluded that the new regime was one of a rapid loss. 2013 and 2014 may be considered to confuse the issue however they are aspects of weather impacting the ice in the post 2007 period. The trend so far may be flat, but there is the emerging picture of greater volatility. Note that by leaving out the 2013/2014 data points the trend is similar to the pre 2007 period due to the overwhelming effect of the minimum of 2012.
We need a lot more years to see whether there will be an inflection from the previous loss rate to a new more level loss rate. However the increasing volatility is to be expected from thinner ice yielding increasing response to weather due to increasing open water formation efficiency.
Both my SIPN extent prediction, and my informal Crysosphere Today area prediction (more) look likely to be marginal fails on the low side, which isn't a bad performance. I won't argue the point but a marginal low fail given that both methods are only designed to be 80% successful isn't too bad a performance. I need to wait for the SIPN extent prediction as that is based on September NSIDC extent, but as things stand, without large losses over the next week or so, if I had reported the bound to 1 least significant digit (4.5) instead of 4.51 million kmsq, it would probably be successful. Maybe that's a lesson for next year...
It is possible I will be moved to post on the SIPN prediction in early October. It is also possible I will post on things that occur to me through the autumn. However as things stand I do not intend to post again until April 2016.
That's in part because my first order of electronic components since the 1990s is being delivered this week. And in part because I have a few measurements to make, with my new Picoscope....
At the rate I am going I have some 100 hours of such measurements (just evenings and weekends) before I have the dataset I need to the accuracy I need.