The median prediction for the mean sea ice extent during the month of September 2021 is 4.39 million km2. According to ARCUS:
As of 22 August 2021, the Arctic sea-ice extent was 5.58 (compared with 25 August 2020 value of 4.43) million square kilometers. Arctic sea-ice extent in 2021 remains well below the climatological median and has closely followed the 2012 values for much of the summer but has diverged to higher sea-ice extent starting in early August. The forecasts continue to support September 2021 mean sea-ice extent being well above the September 2020 value. July sea-ice retreat has been greatest in the Eurasian seas, particularly in the East Siberian Sea, making the 2021 ice edge well north of the long-term median edge in Eurasia. Sea ice retreated since the end of July along the northern coast of Alaska, although the ice edge is near its climatological position, which makes the Beaufort and Chukchi sea ice extent the largest at this time of year since 2006. A tongue of sea ice that has been present all summer continues to extend close to land in the Kara Sea, making the northeast passage likely to remain blocked for the first time in several years. Half the models which provide spatial data to the SIO predict that the tongue is likely to survive.
Now let’s take a look at a range of assorted extent measurements. Here’s the NSIDC’s 5 day average extent:
Next here’s JAXA/ViSHOP extent, generally assumed to be a “2 day average”:
Then there’s the EUMETSAT OSI-SAF version:
and finally, for the moment at least, here is the Alfred Wegener Institute / University of Bremen version:
With September 1st only 3 days away all the assorted extent metrics are above the 5 million km2 level. Will one or more of them manage to get below the SIPN predicted 4.39 million km2 monthly average by September 30th? Will the current “tongue of sea ice” in the Kara Sea survive the summer? How about the multi-year ice still surviving in the Beaufort and Chukchi Seas?[Edit – September 1st]
Here are the end of August numbers for the “high resolution” AMSR2 metrics:
Extent on August 31st is 4.55 million km2. Unlike JAXA’s AMSR2 extent metric, which has been almost flat for the last couple of days, this one has taken a bit of a tumble. Compaction is currently lowest for the date in the AMSR2 record. Unlike extent![Edit – September 15th]
A very tentative minimum is now visible on the JAXA/ViSHOP extent graph. Barring any further declines minimum extent for 2021 was 4.61 million km2 on September 12th.[Edit – September 17th]
In the continuing Google enforced absence of our favourite UH derived metrics I’ve grafted the newly available AWI high resolution AMSR2 area/extent data onto the existing UH numbers. Here is the result:
The join is invisible, and the high resolution AWI AMSR2 minimum Arctic sea ice extent for 2021 currently stands at 4.38 million km2 on September 13th.
Watch this space!