Canada's Last Epishelf Lake Is Gone for Good, Study Confirms

Canada's last epishelf lake — a rare layer of freshwater trapped by the Milne Ice Shelf on northern Ellesmere Island — drained into the Arctic Ocean after the ice shelf's 2020 breakup and will not recover, a new study confirms.

Epishelf lakes form when an ice shelf acts as a dam, trapping a layer of freshwater floating above seawater connected to the ocean. The Milne Fiord epishelf lake, in Nunavut, supported freshwater microorganisms near the surface and marine species below. In July 2020, the Milne Ice Shelf broke apart, losing 45% of its area and removing the barrier that held the freshwater in place.

Drawing on a decade of ocean measurements, satellite imagery and field observations, researchers from the University of British Columbia, the University of Alberta, Université Laval and Carleton University reconstructed the lake's disappearance. The freshwater layer began escaping immediately after the collapse and had mostly vanished by autumn 2020. "The ice shelf and lake had been thinning for decades, but the 2020 breakup was the last straw. The lake drained within months," said Dr. Jérémie Bonneau of Université Laval, a study author.

By July 2022, brackish water had fully replaced the lake's freshwater layer, and annual monitoring since has found no sign of recovery. "Epishelf lakes can signal when an ice shelf is under stress, and that's what we saw here," said co-author Dr. Bernard Laval of the University of British Columbia. "The data showed the ice shelf was failing. Once the ice is gone, the ecosystem goes with it. There's no coming back."

The Milne Ice Shelf lies within the "Last Ice Area," a region expected to retain perennial sea ice longer than anywhere else in the Northern Hemisphere, and within the Tuvaijuittuq Marine Protected Area, whose name means "the place where the ice never melts" in Inuktitut.