Arctic sea ice, a key indicator of climate change, melted to its lowest level on record this year before beginning its autumnal freeze, US researchers say.
The extent of ice probably hit its low point on September 16, when it covered 3.42 million square kilometres of the Arctic Ocean, the smallest amount since satellite records began 33 years ago, according to the US National Snow and Ice Data Center (NSIDC).
Changing weather conditions could further shrink the extent, the centre said. A final analysis is expected next month.