Arctic sea-ice cover following this summer’s melt was the sixth lowest on record, the US National Snow and Ice Data Center in Boulder, Colorado, announced on 27 September.

Sea-ice extent bottomed out for the season at 4.59 million square kilometres, tying levels seen in 2008 and 2010. The sea ice reached its last minimum this year on 23 September, which is one of the latest dates observed for this annual occurrence.

The most recent calculations, from 2017, show that Arctic sea-ice coverage each September has declined by 13.2% per decade. A relatively cool July helped to slow this year’s rate of loss.

Since satellite records began in 1979, the 12 lowest extents have all happened in the past 12 years. The record low came in 2012, at 3.39 million square kilometres.