Since 1992 it has averaged a net loss of 65 million metric tons of ice a year. All maps by JASON TREAT, MATTHEW TWOMBLY, WEB BARR, MAGGIE SMITH, NGM STAFF. ART: KEES VEENENBOS.

The loss of sea ice in the Arctic has been one of the most visible signs of climate change on the planet over the past four decades. According to the Intergovernmental Panel on Climate Change ...