Canada’s last remaining epishelf lake has completely and permanently drained into the Arctic Ocean following the breakup of the Milne Ice Shelf, according to a new scientific study published in Scientific Reports. Located on northern Ellesmere Island in Nunavut within the Milne Fiord, the body of water was the last large epishelf lake still standing in the Canadian Arctic.
Collapse of Canada’s Last Epishelf Lake
In July 2020, the Milne Ice Shelf collapsed, losing between 40% and 45% of its surface area in just two days and shrinking by approximately 30 square miles (80 square kilometers). The floating ice sheet had previously acted as a natural dam blocking the mouth of the fjord, trapping freshwater runoff from glaciers above the denser saltwater of the ocean.
When the ice barrier failed, the trapped freshwater began escaping immediately. Field measurements showed that the freshwater layer had mostly vanished by autumn 2020. By July 2022, brackish water had fully replaced the lake’s distinct freshwater layer, and annual monitoring since then has confirmed no sign of recovery.
Unique Ecosystem Lost
Epishelf lakes are rare polar formations that support distinct ecological structures. In the Milne Fiord lake, freshwater microorganisms thrived near the surface while marine species lived in the ocean below, separated by a sharp salinity boundary known as a halocline.
Researchers who drilled into the outflow channel beneath the ice shelf in 2017 previously observed a robust marine ecosystem in complete darkness, featuring brittle stars, sea anemones, and scallops. 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,
Dr. Andrew Hamilton, an arctic oceanographer and research scientist at the University of Alberta who completed his PhD research at Milne Fiord, said in a statement. When the ice shelf broke apart, that unique ecological structure disappeared. It was the last of its kind in Canada.
With the structural integrity of the remaining ice shelf gone, freshwater entering Milne Fiord is now flushed directly into the ocean. Researchers note that the ecosystem cannot return under current climate conditions. These systems took thousands of years to form and were lost in months,
said study author Dr. Jérémie Bonneau, a professor of civil and water engineering at Université Laval. On any human timescale, they are not coming back.
A Decade of Data and Ongoing Changes
To reconstruct the collapse, an interdisciplinary team of researchers from the University of British Columbia (UBC), the University of Alberta, Université Laval, and Carleton University drew on a decade of ocean measurements, satellite imagery, and field observations. The team had monitored changes to the ice sheet since 2011, tracking its transformation amidst warming temperatures.
Dr. Bernard Laval, a professor of civil engineering at UBC who leads its environmental fluid mechanics research group, noted that the data consistently demonstrated the failure of the ice shelf. Once the ice is gone, the ecosystem goes with it.
There’s no coming back.
The research team also included co-authors Silas Pijamini and Joseph Shoapik from Ausuittuq (Grise Fiord), who have participated in fieldwork in the region since 2022.
Implications for the Last Ice Area
The Milne Ice Shelf is situated within the Last Ice Area, a region of the Northern Hemisphere expected to retain perennial sea ice longer than anywhere else, and lies inside the Tuvaijuittuq Marine Protected Area—whose Inuktitut name translates to the place where the ice never melts.
The rapid drainage of the epishelf lake demonstrates that even these expected long-term ice refuges are vulnerable to climate warming. Scientists designed the monitoring project to track the transition of the fiord from a system with an active ice shelf and epishelf lake into one that is seasonally ice-free, anticipating further profound changes in the fjord ecosystem in the coming years.