If global warming continues unabated, humans are likely to completely remake the map of the Arctic in a few decades

The number of open water days per year — meaning days without sea ice — increases significantly in the Arctic region between 1920 and 2100, according to a new modeling study. (Individual images: Katy Barnhart. Animation: Tom Yulsman) Ice was in the news quite a lot last week. There was, for example, the news that Antarctica could be gaining, not losing, ice, at least for now. Lest you were tempted to breathe a sigh of relief, critics pointed to contrary evidence. And there were also these unsettling findings about the gigantic West Antarctic Ice Sheet. But far to the north, some equally important news unfortunately got less attention. For the long and short of it, see the animation above. I created it to portray in visual form what a study published last week has revealed: Unless we start reining in greenhouse gas emissions, "our projected impact on the climate system will change the face of Arctic sea ice," says Katy Barnhart, who led the study while she was at the University of Colorado's Institute for Arctic and Alpine Research. (Full disclosure: I'm a professor at the University of Colorado.) The animation shows computer model simulations of how Arctic sea ice is likely to respond to continued human-caused warming. More specifically, it models how the number of days of open water change each year from 1920 to 2100 under a "business-as-usual" scenario. By 2100, according to the study, much of the Arctic has greater than 150 additional days of open water as compared with the pre industrial period prior to 1850. But we won't have to wait that long to see significant changes. If greenhouse gas emissions continue to rise, the entire coastline of the Arctic, and most of the Arctic Ocean itself, will see at least 60 additional days a year of open water by mid-century. Some sites will even see 100 additional open water days. Arctic sea ice has already shrunk in geographic extent during the period of modern observations. This has been one of the significant signs and symptoms of human-caused warming. But for people and other species in the Arctic, something else is even more important than an overall, general decrease in ice extent: What's going to happen in their neck of the woods? With that in mind, Katy Barnhart, and her colleagues, sought to produce a detailed forecast of open water patterns in the Arctic. Among the questions they sought to answer were these: