Canada's last epishelf lake has vanished after the 2020 breakup of the Milne Ice Shelf, according to a new study. Epishelf lakes form when an ice shelf acts as a natural dam, trapping a layer of freshwater above seawater. These unique ecosystems support freshwater microorganisms near the surface and marine species below, separated by a thin boundary of fresh and salt water. The Milne Fiord epishelf lake, located on northern Ellesmere Island in Nunavut, was one of the last of its kind. It had been thinning for decades, but the 2020 breakup marked a turning point. The ice shelf lost 45% of its area, removing the barrier that held the freshwater in place. Researchers from universities in Canada, including UBC, University of Alberta, Université Laval, and Carleton University, used a decade of ocean measurements, satellite imagery, and field observations to track the lake’s disappearance. Their findings show that the freshwater layer began escaping immediately after the ice shelf collapsed and had mostly vanished by autumn 2020. By July 2022, brackish (slightly salty) water had fully replaced the freshwater layer. Annual monitoring since then has found no sign of recovery. The ice shelf and lake had been thinning for decades, but the 2020 breakup was the last straw. Epishelf lakes are rare and ecologically significant. They serve as indicators of ice shelf stress, as noted by co-author Dr. Bernard Laval of UBC. The data showed the ice shelf was failing. Once the ice is gone, the ecosystem goes with it. There's no coming back, said Dr. Jérémie Bonneau of Université Laval, who led the study. Dr. Andrew Hamilton of the University of Alberta explained that these lakes are remarkable because they allow a freshwater ecosystem to exist directly above a marine one, separated by a thin boundary. When the ice shelf broke apart, that unique ecological structure disappeared. The research team, which included Inuit scientists from Ausuittuq (Grise Fiord), has been monitoring the region for nearly two decades. Their long-term data collection allowed them to reconstruct the lake's drainage and its transformation from a freshwater ecosystem into a marine environment. The study, published in Scientific Reports, shows that freshwater entering Milne Fiord is now flushed directly into the ocean, as the remaining ice shelf can no longer contain it. Re-establishing the lake would require the ice shelf to recover, which is not possible under the current climate trajectory. 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. It is also within the Tuvaijuittuq Marine Protected Area, whose name means "the place where the ice never melts" in Inuktitut. The loss of the lake shows that even this potential refuge for ice-dependent ecosystems is undergoing rapid change. The study emphasizes that these systems, which took thousands of years to form, were lost in months. On any human timescale, they are not coming back.