The time has arrived to start taking a close look at the assorted different Arctic sea ice extent metrics, in order to ascertain their respective maxima for 2025. To begin with here’s Zack Labe’s overview of previous years’ maxima:
It now seems highly likely that 2025’s maximum extent will ultimately prove to be the lowest in the satellite era. The remaining question is when this year’s maximum will occur.
My speculation yesterday that AWI’s flavour of Arctic sea ice extent had already achieved its maximum value for 2025 has been negated today:
The NSIDC 5 day average and JAXA extent metrics are also currently at their maximum levels for the year so far, so let’s wait and see which one is the first to take a downward turn.
On March 22, Arctic sea ice likely reached its maximum extent for the year, at 14.33 million square kilometers, the lowest in the 47-year satellite record. This year’s maximum extent is 1.31 million square kilometers below the 1981 to 2010 average maximum of 15.64 million square kilometers and 80,000 square kilometers below the previous lowest maximum that occurred on March 7, 2017.
After spending several weeks in the unfortunate position of lowest for the date, JAXA/ViSHOP Arctic sea ice extent has just risen above 2015. By a mere 10,000 km²:
Despite the fact that JAXA extent is still rising, AWI extent has potentially already achieved its maximum value for 2025:
Somewhat belatedly, here is the PIOMAS sea ice thickness map for February 28th 2025:
At the end of February Arctic sea ice volume had increased to 19.32 thousand km³, still 2nd lowest for the date in the PIOMAS record:
AWI have also released a new version of their thickness product, incorporating additional data from the two Sentinel 3 satellites. The thickness data for February 28th, looks slightly different:
The New Year began with JAXA/ViSHOP extent lowest for the date in the satellite era, just below 2018 . Since then extent has reduced, and there is now a large gap:
The primary reason for this is the remaining open water in Hudson Bay:
In previous years Hudson Bay has been covered by sea ice by this time of year, but in 2025 a large area remains unfrozen in early January!
Due to the way PIOMAS handles the leap years the last gridded thickness data of 2024 is dated December 30th:
By December 30th Arctic sea ice volume had increased to 13.61 thousand km³, 2nd lowest for the date in the PIOMAS record:
Christmas is coming, and even as we speak Snow White is heading for the geographical North Pole to assist Santa’s little helpers in their annual gift delivery mission:
Santa at the North Pole in August 2016
We’ll start the festive season with a graph of JAXA/ViSHOP extent, which is in a “statistical tie” with 2020 for 2nd lowest for the date in the satellite era:
The Laptev and East Siberian Seas have now refrozen. Consequently Arctic sea ice extent is now increasing more slowly, and JAXA/ViSHOP extent is 3rd lowest for the date in the satellite era:
Note the change in scale from previous months, to allow for easier comparison with the “near real time” CryoSat-2/SMOS merged thickness data from the Alfred Wegener Institute:
The JAXA extent graph is currently not updating, so let’s begin this month with the latest AMSR2 sea ice concentration map from the Alfred Wegener Institute. Click the image to see a ~10 Mb animation of the last four weeks:
Note in particular the restart of export into the East Greenland Sea via the Fram Strait:
and the movement of ice within the Canadian Arctic Archipelago:
The PIOMAS gridded thickness data for September 2024 has been released:
Earlier today the National Snow and Ice Data Center announced that:
On September 11, Arctic sea ice likely reached its annual minimum extent of 4.28 million square kilometers (1.65 million square miles). The 2024 minimum is the seventh lowest in the nearly 46-year satellite record. The last 18 years, from 2007 to 2024, are the lowest 18 sea ice extents in the satellite record…
Note that this is a preliminary announcement. Changing winds or late-season melt could still reduce the Arctic ice extent, as happened in 2005 and 2010. NSIDC scientists will release a full analysis of the Arctic melt season, and discuss the Antarctic winter sea ice growth, in early October.
Consequently several of the usual cryodenialospheric suspects have been frantically spinning their webs of deceit around the announcement.
First up was Javier Vinós, who beat the NSIDC’s starting gun by firing a broadside on X (formerly Twitter) on Sunday. If you’re unfamiliar with the name, Javier frequently pontificates about Arctic sea ice, amongst other things, on Judith Curry’s “Climate Etc.” blog. He confidently announced that:
Arctic sea ice reaches its annual minimum with an extent greater than in 2007, 2012, 2016, 2019, 2020 and 2023.
The two warmest years in a row at > +1.5°C have ZERO IMPACT on the 17-year resilience of Arctic sea ice.
Needless to say, “Snow White” felt compelled to quibble:
On several previous occasions “Snow White” and I have documented Ron Clutz’s misuse of MASIE Arctic sea ice extent data on his “Science Matters” blog. We agree with Ron that science matters, so on several occasions we have attempted to direct his attention to my interview with NASA/NSIDC scientist Walt Meier. Walt’s words of wisdom included:
Year-to-year comparisons and trend estimates will be more accurate in the passive microwave data than in MASIE.
It will probably not surprise you to learn that Ron has not learned anything from our repeated efforts. In his article entitled “2024 Arctic Ice Beats 2007 by Half a Wadham” earlier today Ron proudly displays this graph:
You will note that Ron does not provide details of his data source. However I have recently noted a sudden lack of SSMIS passive microwave data emanating from NOAA. The OSI SAF reported it this way on September 12th:
Dear OSI SAF Sea Ice Concentration User,
Due to missing input data, we have not been able to generate L2 products, corresponding to F-16 / F-17 / F-18 since Sep 11 19:36 UTC.
We apologize for any inconvenience.
The NSIDC’s sea ice home page puts it this way today:
Now day 260 of 2024 is September 16th, so it seems safe to assume that Ron is erroneously using his favourite MASIE metric for year to year comparisons yet again. In his article Ron states that:
SII was reporting deficits as high as 0.5M km2 (half a Wadham) compared to MASIE early in September. For some reason, that dataset has not been updated for the last five days.
It appears as though Ron has also not yet learned how to find NSIDC’s sea ice home page on the world wide interweb!
I added this hopefully helpful comment below Ron’s article. For some strange reason it is yet to emerge from his moderation queue:
[Update – September 18th]
Our regular reader(s) will not be surprised to learn that my helpful comment yesterday is no longer in Ron’s moderation queue, but is now languishing underfoot on his cutting room floor.
Ron has written another Arctic article using the graph reproduced above. This one is entitled: “2024 Arctic Ice Abounds at Average Daily Minimum“. In it Ron assures his flock of faithful followers that:
We are close to the annual Arctic ice extent minimum, which typically occurs on or about day 260 (mid September). Some take any year’s slightly lower minimum as proof that Arctic ice is dying, but the image above shows the Arctic heart is beating clear and strong.
Over this decade, the Arctic ice minimum has not declined, but since 2007 looks like fluctuations around a plateau.
Ron has also changed his phraseology regarding the recent SSMIS data outage. This time it reads:
For some reason, apparently data access issues, that dataset has not been updated for the last five days.
“Snow White” felt compelled to leave Ron another helpful comment concerning his new words of Arctic wisdom:
Watch this space!
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