This may look like leftover spaghetti but it is a picture of the ups and downs, peaks and troughs, of the annual cycles of Arctic sea ice cover over the past 40+ years based on satellite data – courtesy of NSIDC.
What I would like you to pick from this is the blue line which represents the data for 2020. That’s the blue line which stands out from most of the others near the bottom of the image across the months of July to November.
As well as being the second lowest year for sea ice extent in modern times, at a little under 4 million square kilometres, this year also holds the absolute record for the longest period where there has been less than 6 million square kilometres of sea ice – almost three months – a quarter of the year. The previous such record being set last year, 2019 (dark green line). Is that significant? Damn right it is. The longer the time spent with lower levels of ice cover obviously means the more warmth the ocean is going to accumulate, making it more difficult for fresh ice to build up over the following colder part of the year. You can see the importance of that I hope.
One more point. While 6 million square kilometres of ice, trending down to 4 million at the annual low point (from now about 14 million at winter peak) may seem like a lot of ice, it needs to be recognised that to qualify as being ice-covered, a square kilometre of ocean needs only to have 15% cover of ice – that’s one eighth of the surface water. So a sizeable number of those total square kilometres of ocean waters are going to be much less than half covered by ice. Makes you stop and think, doesn’t it?