Arctic sea ice has been in the media quite a bit this month and we looked at the issue in a blog a couple of weeks ago.
Figures from the NSIDC show this year extent fell to 5.10 million square kilometres on 13 September, and the ice cover is now increasing as we head into the northern hemisphere winter.
It’s possible that a shift in wind patterns or a late season melt could push ice extent lower, but – assuming the current figure remains – this year’s minimum extent is the sixth smallest since satellite records began in late 1970s.
The five lower seasonal minimum ice extents all happened from 2007 onwards, with the record set last year. That record low was just 3.41 million square kilometres, a notably low figure that was likely to have been influenced by weather conditions over the region which accelerated ice loss.
While a detailed analysis is required to understand the exact causes of the seasonal minimum this year, the weather conditions during the summer have been less conducive to ice loss than those experienced last year.
From late May to late June a stream of storms entered the Arctic Ocean, creating cloudy conditions at the time when the sun was at its strongest.
Relatively high ice cover during June and July (compared to recent years) was likely to have delayed the warming of the upper ocean and reduced melting at the base of the ice towards the end of the melt season.
We do expect a year to year variability in sea ice extent precisely because it can be so heavily influenced by weather patterns, but there is a long-term picture of decline – as you can see in the graph of August ice extents below.
New ice thickness data from the Cryosat satellite has also been released recently, and this shows a continuing shrinkage of winter ice volume. This provides a timely reminder that despite the modest recovery in seasonal minimum ice extent this year, the ice continues to thin and the volume of sea ice continues to shrink.