So-called "Storm Frank" over Iceland in December 2015. (Credit: Icelandic Met Office) The height of last winter – from December through February – was the warmest on record, shattering monthly marks for the least Arctic ice seen since satellite observations began in the 1970s. And now a new study in an American Meteorological Society journal shows how those temperatures combined with an unusual storm system to wreak havoc on the Arctic sea ice pack. As seasons change and Earth’s northern axis tilts away from sun, ocean water freezes into sea ice around the pole. But many regions remained ice-free later than normal last winter. And for the Barents and Kara Seas, the region north of Scandinavia and Russia, the freeze-up came some two months late, leaving a brittle ice pack. Then, as people were celebrating holidays in the final moments of 2015, a cyclone started forming in the North Atlantic Ocean. The cyclone pushed its way toward the United Kingdom, then intensified as it moved passed Iceland and along Greenland’s east coast, reaching the central Arctic on New Year’s Eve. This Arctic cyclone brought freakishly warm and moist air around the North Pole, pushing winter temperatures above freezing.