It’s another climate calamity. Greenpeace has said this year’s decline in the extent of Antarctic sea ice was unprecedented since measurements began.
It goes to show that some climate watchers have no idea about natural variation seeing every change as being due to creeping climate change. Such is the case with reporting of recent data from the National Sea Ice Data Center which shows that this year Antarctic sea ice reached the lowest extent on the satellite record (post 1979). The previous record was set in March 2017, of 2.1 million square kilometres, but by 20 February this year it was 1.98 million square kilometres.
The extent of Antarctic sea ice is very sensitive to atmospheric and oceanic conditions. It will grow when it’s cold enough and because there are no land barriers the ice is thin meaning it can be moved easily by winds, covering a large area. This year the record low was partly due to strong winds pushing ice away from the Ross Sea . This is not due to global warming, it’s natural variability, or in other words, weather.
This year’s record low occurred in a similar way as the 2017 low. Both times there was an earlier than average maximum sea-ice extent, followed by rapid decline. Since 2017 the sea-ice extent stayed well below average for two years, returning to near-average in 2020.
You only have to take a quick look at the data to realise that Antarctic sea ice has a lot of year-to-year variability, see figure 1 from the journal Nature. The highest Antarctic sea-ice minimums were reached in 2008 (3.69 million square kilometres) and 2013 (3.68 million square kilometres) but in 2015 and 2016 the minimum dropped considerably. With this much variability it is hardly surprising a record low has been attained this year.
Such interannual variability contradicts the predictions of some climate models that it should decrease in response to increased greenhouse-gas emissions. Global warming could have a role in this new record, but it is far too early to tell. I expect that next year the extent of sea ice reverts back to average.
For a complete view of both poles Fig 2 shows the extent and trends of sea ice for the north and south poles. Courtesy NSIDC.