In a predictable yet mildly troubling reminder of the Arctic’s continued ice melt, researchers say yet another massive ice chunk has broken off from an ice shelf in Canada. The Serson Ice Shelf just saw its mass more than halved when two large sections broke off recently, leaving it about 47 square miles smaller. For those of you keeping track at home, this summer has seen 19 square miles of the Markham Ice Shelf break off and float into the sea, as well as an 8.5-mile section of the Ward Hunt shelf. “These changes are irreversible under the present climate and indicate that the environmental conditions that have kept these ice shelves in balance for 4,000 years are no longer present,” said Trent University’s Derek Mueller. Ice shelves are made of very old floating sea ice that’s still attached to land; the surrounding sea ice usually acts to brace the shelves against wind and waves, but this year’s and last year’s were not much help. “We have now reached a threshold where [the environment] is too warm for these ice shelves to exist anymore,” said Luke Copland of Ottawa University.