Canada's last epishelf lake permanently lost after 2020 ice shelf collapse

In July 2020, an ice shelf on northern Ellesmere Island fractured and lost nearly half its mass. Within months, Canada's last epishelf lake—a rare freshwater ecosystem that had persisted for thousands of years—drained entirely into the Arctic Ocean. A decade of research now confirms what scientists feared: it will not return.

Epishelf lakes are geological oddities. They form when a floating ice shelf acts as a dam, trapping a layer of fresh water above the ocean's salt water. The Milne Fiord epishelf lake, located in Nunavut, was home to freshwater microorganisms near its surface and marine species below—two distinct ecosystems separated by a thin boundary between fresh and salt. When the Milne Ice Shelf broke apart in 2020, losing 45 percent of its area, that barrier vanished.

Researchers from UBC, the University of Alberta, Université Laval, and Carleton University spent a decade collecting ocean measurements, satellite imagery, and field observations before and after the collapse. What they found was stark: the freshwater layer began escaping immediately after the ice shelf fractured and had mostly disappeared by autumn of that same year. Instruments left in place during the 2020 field season—which was cancelled due to COVID-19—recorded the lake's rapid transformation into brackish water, though researchers could not retrieve the data until two years later. By July 2022, when field measurements resumed, the lake's distinct freshwater layer had been completely replaced by marine water. Annual monitoring since has found no sign of recovery.

Dr. Jérémie Bonneau, a professor of civil and water engineering at Université Laval who conducted part of the research during his PhD at UBC, described the collapse as inevitable. "The ice shelf and lake had been thinning for decades, but the 2020 breakup was the last straw. The lake drained within months," he said. The research, published in Scientific Reports, represents the first complete reconstruction of the lake's drainage and its shift from a freshwater ecosystem into a marine environment.

The loss carries particular weight because 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 situated within the Tuvaijuittuq Marine Protected Area, whose name means "the place where the ice never melts" in Inuktitut. Even this potential refuge for ice-dependent ecosystems is undergoing rapid change. Dr. Bernard Laval, a professor of civil engineering at UBC, noted that epishelf lakes serve as early warning systems. "The data showed the ice shelf was failing. Once the ice is gone, the ecosystem goes with it. There's no coming back," he said.

Re-establishing the lake would require the ice shelf to recover—something that is not possible under the current climate trajectory. Dr. Derek Mueller, a professor of geography and environmental studies at Carleton University who established the research program tracking the ice shelf and lake, emphasized the commitment required to document Arctic change. "There are much easier places to conduct research, but understanding change in the High Arctic requires returning year after year," he said. The research team included co-authors Silas Pijamini and Joseph Shoapik from Ausuittuq (Grise Fiord), who have participated in fieldwork since 2022.

Dr. Andrew Hamilton, a research scientist at the University of Alberta who completed his PhD research at Milne Fiord, reflected on what was lost. "Epishelf lakes are remarkable because a freshwater ecosystem sits directly above a marine one, separated only by a thin boundary between fresh water and salt water. When the ice shelf broke apart, that unique ecological structure disappeared." Bonneau offered a final measure of the loss: "These systems took thousands of years to form and were lost in months. On any human timescale, they are not coming back." The research team anticipates further profound changes in the coming years as Arctic warming continues to reshape the region.