The Maud Rise polynya has been sporadically opening up in Antarctica's ice since at least the 1970s. Now climatologists finally know why.

During the winters of 2016 and 2017, a hole the size of Switzerland opened in the middle of Antarctica's sea ice. And scientists just figured out how it came to be.

Every now and then for the last 50 years, an enormous hole opens up in the Antarctic sea ice. And by enormous, we mean truly enormous — the feature in question was twice the size of Wales last time it appeared in 2016 and 2017.