A last-minute surge of sea ice in the Arctic has saved the 2017-18 season from being the record lowest minimum (fig 1). The figure for the 13th of March of 14.453 was 6,000 square kilometres higher than last years record lowest of 14.447 million square kilometres on the 5th of March 2017 (fig 2). There is a possibility that this surge could go on for a little longer, although we have now passed the average date of the maximum in the Arctic.
Of course the NSIDC have changed how they do their statistics recently, and now use a moving average of the extent over a number of days, rather than the highest value for a single day that I use, so I don’t know what they’ll finally decide.
I’ve been watching polar sea ice extents for almost 10 years now, and download, parse and visualise the data using a Windows application that I’ve developed. I still think of all the various ways to visualise sea ice extent data in both Arctic and Antarctic is by means of a 365 day rolling average chart, which of course removes any seasonality out of the data series. I’ve done quite a bit of research in those 10 years to write the various articles I publish in this blog but never come across a chart like this. Here are the latest charts for both poles that I’ve generated using that application.
The steady decline in Arctic sea ice is still very much in evidence in the 365 day moving average, but recently the sharp fall that started in 2014, has been arrested (fig 1).
Meanwhile in the Antarctic the sharp rise that started at the beginning of 2012 is clearly visible, as is the even sharper fall in extents that began in the summer of 2015, but it’s interesting to see that since last Autumn that fall has also been arrested as well (fig 2).
Not a lot of people know that
You might have noticed that I’ve added an average line to both charts for the last 39 years. They show how well-balanced the annual average ice extent are between Arctic and Antarctic in that time, at 11.238 and 11.764 million square kilometres respectively – not a lot of people know that.
It’s still neck and neck as far as the lowest maximum sea ice extent is concerned in the Arctic. The 2017-18 season has it all to do if its to exceed the 14.447 million square kilometres of the record lowest set only last season. On the 1st of March, the two season were tied at 14.358 million square kilometres (fig 1). I calculate the average date of maximums in the Arctic is the 8th of March, so the question is can this season can keep this late surge going and make up that 89,000 square kilometres during the next week? I apologise for the articles I write about sea ice extent, which invariably end up sounding like a commentary on a horse race!
Minimum Antarctic sea ice this season just finished a smidgen above last year (fig 1). This season didn’t hang around like last season and has pulled up rather sharply in the last week. As far as I can see the minimum of 2.15 million square kilometres occurred on the 18th of February, slightly higher than 2.075 of last season (fig 2). It’s still far from a rosy picture though on the 1st of March the extent was just 77.8% of average for that day.
The Arctic Sea ice has rallied since my last report 10 days ago, and it’s finally made it through the 14 million square kilometre extent barrier (fig 1). It’s a shade higher for the 22nd of February than it was on the same day in the 2015-16 season, and although there’s a chance for a little more growth, it still looks highly likely that it will snatch the title of lowest maximum from last season.
Meanwhile, in the Antarctic this season may well have escaped the title of lowest minimum this season. The total extent for the 22nd was marginally a little higher than it was in last years record low season for the same day, and the minimum may have already occurred, which on the average occurs on the 20th of February down there (fig 2).
It looks very like the 2017/18 Arctic sea ice maximum will beat the record low set only last year. At the moment (14th Feb) the anomaly stands at just 90.4% of the average for this day of the year, that’s 2.3% lower than it was this time last year, and equates to a massive 352,000 square kilometre less of sea ice (fig 1).
The fact that we are now in the grips of a SSW event doesn’t bode well for a late surge in sea ice as we approach the time of maximum in the Arctic. The mean date for the maximum is the 8th of March, and although unlikely, the maximum may have already occurred! The maximum so far this season occurred over a week ago now on the 5th (13.979 million square kilometres) which would make it extremely early, because the earliest maxima on record in the last 40 years occurred on the 21st of February in the years 1987, 1994 and 1996 (fig 2).
The Arctic Sea Ice extent is currently the lowest on record for any January 2nd since the satellite series started forty years ago. To be fair this season has been playing nip and tuck with last season (fig 2), but at the moment the 12.542 million square kilometers, which is 90.6% of the average for this day, is slightly lower than the 12.614 at the same time last year (fig 1). This news caught me out a little, because the last time I looked sea ice extent in the Arctic was holding up quite well. The reason behind this is probably down to the fact that the Arctic has been even milder than usual and had a bad Christmas, a bit like the sales figures at Debenhams.
It might be thinner than ever, but Arctic sea ice this Autumn is doing much better than it did last year, with the sea ice extents up by around 800,000 square kilometres at 88.2% of the 1981-2010 long-term average, compared with being only 81.0% of average in November 2016 (fig 1).
In the Antarctic things are also not quite as dire as they were last Autumn, and although this Autumns sea ice extent is tracking well below the x 2 standard deviation area (light grey) at 91.6% of the 1981-2010 long-term average, it’s almost a million square kilometres higher than at the same time last year (fig 2).
There’s the usual ring of abnormally high positive temperature anomalies around the Arctic at the start of November (fig 1). I had a theory that the largest anomalies were located in areas of open water where no sea ice had formed, but this theory doesn’t look too plausible judging by the latest sea ice extent chart (fig 2). I notice that the recent cold weather in Canada has encouraged early ice formation around the coast of the Hudson Bay, but the area to the north of the Chukchi sea look severely depleted of any sea ice again for this time of the year.
The National Geographic magazine have just noticed a large increase in the Weddell Sea polynya (south of south America) that I brought to your attention earlier last month in an article that I found on the phys.org website. I can confidently predict that the polynya will continue to increase in size till it totally disappears later in the Antarctic summer!