The sea ice in the Arctic Ocean grows and shrinks with the seasons. From September to March, it expands in the darkness, locking water into island-sized solids. During the summer months, it recedes, as the water rejoins the atmosphere and sea.On September 11 of this year, the sea ice in the Arctic Ocean reached its annual minimum. 2015’s minimum was the fourth-smallest ever recorded, and it nearly tied with the third-smallest on record. Which makes a certain amount of sense: In the satellite era, the ten worst years for Arctic sea ice have been the last ten.

In some maps, it can sometimes be hard to discern the northern sea ice. In satellite images—often the best representation available—the oceanic ice melds into the larger Arctic ice cap, which includes glaciers and ice sheets in Greenland, Canada, and Russia. That’s why I like this visualization, from developers at Mapbox, a mapping and data startup based here in D.C. It shows how the sea ice has changed—not the entire ice cap—through the satellite record. In particular, I think it reveals how bad things have gotten recently—and how small the oceanic ice was in 2012, the lowest ever recorded.