This September, the extent of Arctic sea ice shrank to roughly 4.7 million square kilometres, as was determined by researchers at the Alfred Wegener Institute, the University of Bremen and Universität Hamburg. Though slightly larger than last year, the minimum sea ice extent 2017 is average for the past ten years and far below the numbers from 1979 to 2006. The Northeast Passage was traversable for ships without the need for icebreakers.