The reason it is a mystery is because that increase in sea ice coverage is contrary to the theory of global warming. (theinconvenientskeptic.com)
But turning imagery of floating ice into reliable estimates of ice coverage remains a challenge. (dotearth.blogs.nytimes.com)
Scientists explain the heat wave by pointing to a string of record - breaking hot months earlier this year, coupled with little ice coverage during the summer. (buzzfeed.com)