Continent surrounding the South Pole, located almost entirely within the Antarctic Circle. It is covered by an ice cap up to thirteen thousand feet thick and is characterized by extremely low temperatures.
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.
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 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).
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!
It looks like this Winters maximum sea ice extent has been reached in the Antarctic a little earlier than average. The spot value for the 12th of September was 18.023 million square kilometres was the lowest maximum in the satellite record that started in 1979, but it was a very near thing, because the 2017 figure was just 4,000 square kilometres lower than the previous lowest maximum of September 1986. The sea ice could surge again and prove me a liar, but I got it right with the Arctic minimum, so maybe I’m on some kind of roll (pardon the pun).
Here is the table sorted from lowest to highest on maximum extent (fig 2). Before you ask 1978 is top of the list because the satellite record started on the 26th of October 1978, and the maximum for that year will have occurred a month earlier and been considerably higher than that figure, blame it on the programmer.
I would say on balance that the Antarctic sea ice extent has bounced back extremely well after what was a pretty dreadful start, back on the 1st of March sea ice extent was just 69.8% of the long-term average for that date, on the 12th of September they were back up at 97.4% of the long-term average for that day. This is the latest rather interesting ice extent picture for the Antarctic from the NSIDC (fig 3), which shows another polynya in the Weddell sea similar to the one in the news item I posted earlier this month. Who knows, maybe if that polynya hadn’t opened up, 2017 might not have been the new record low year!