Having been exceptionally low for much of this year the overall extent has not declined as strongly as it might. So extent is no longer the lowest since 1979.
Comparing the 7 day extent averages for the end of April and the end of June it can be seen that whilst extent was strongly at record low levels in April, by now it has lost the lead.
Taking the average extent for the last 7 days of June 2016 is the second lowest, lower then 2012 which ended up the lowest September extent by some margin. However the lowest extent in 2010 was not a record low September extent due to survival of ice in the East Siberian Sea, something suggested by current extent data and by Slater's persistence model, both of which will be addressed shortly.
Extent in the Arctic Ocean however remains strongly lower than other recent years, which makes it the lowest since 1979.
This is a result of the ice edge in the Atlantic sector (Barents and Greenland Seas mainly). The following plot shows the anomaly from the 1981 to 2010 average extent and the Atlantic sector accounts for most of the below average extent this year.
Compactness is the ratio of Area and Extent, in the Arctic Ocean this is not exceptionally low.
In the Peripheral Seas extent loss has stalled. The ice edge must move through the Peripheral region for strong losses in the Central Arctic.
Compactness in the Peripheral Seas is within the set of recent years, not unusually low as was the case in 2007 and 2012 (record years). The title of the following graph is wrong, it is for the Peripheral Seas, not the Arctic Ocean.
The Peripheral Seas can be broken down into contributions from the Alaskan (Beaufort/Chukchi Seas) and Siberian (East Siberian/Laptev Seas) sectors.
Losses in the Alaskan Seas were above average until June, when the losses switched to being below average. This reflects a massive shift in the atmospheric regime, from a dominant high pressure state in May to a dominant low pressure state in June. The Siberian sector is not showing above average losses. This might be significant, in 2010 the end of the summer was marked by a persistent mass of ice in the East Siberian Sea, Bremen, Dr Slater's persistence predictions may be suggesting something similar. And this might be connected to wind driven export from the Beaufort and Chukchi Seas over winter.
The striking difference between the May and June pressure regimes is shown in the following two graphics from NCEP/NCAR.
May sea level pressure. (NCEP/NCAR)
June sea level pressure. (NCEP/NCAR)
So what of the rest of the summer, if we rule out a record low that still leaves interesting play for the position of September 2016 in the rankings. The weather forecast for the coming weeks remains mixed, what of predictions?
Dr Andrew Slater has been publishing a sea ice concentration persistence based predictions this year and last. The current situation suggests an extent in mid August extent similar to last year.
Along with others Dr Slater has entered the Sea Ice Prediction network which has recently reported the predictions made in early June.
Not long until September...