Canada’s last remaining epishelf lake is gone

Milne Fiord Fresh Water Lake on Ellesmere Island

Canada’s unique aquatic landscape has lost its final intact epishelf lake. A multi-institutional research team has confirmed that the freshwater body sitting atop the saltwater of Milne Fiord on Ellesmere Island in Nunavut has entirely vanished, taking a specialized ecosystem down with it (Mirage News). The sudden drainage follows the structural failure of the Milne Ice Shelf, which broke apart in 2020 under accelerating warming temperatures in the High Arctic.

How Milne Fiord Held Canada’s Last Epishelf Lake for 4,000 Years

Epishelf lakes form under rare geophysical conditions where glacial meltwater is trapped behind an ice shelf dam, creating a stable layer of freshwater that floats directly on top of denser ocean saltwater. Because freshwater is less dense than marine water, the two layers do not easily mix. In Milne Fiord, a layer of ice about 50 to 100 centimetres thick covered the lake year-round, protecting the freshwater and saltwater layers from winds that could have mixed them together — and making the lake invisible from the surface.

Evidence cited in the study indicate that the epishelf lake had accumulated and sustained freshwater for more than 4,000 years. When researchers first surveyed the site in 1983, the freshwater layer reached 18 meters in depth — equivalent to the height of a six-story building CBC reports.

University of Alberta and Université Laval Research Teams

An interdisciplinary team from the University of Alberta, Université Laval, the University of British Columbia, and Carleton University had monitored the ice shelf and fjord since 2011 using moorings, satellite imagery, and annual water profiles. According to Mirage News, researchers noted that while the ice shelf had been thinning for decades, the 2020 breakup removed the barrier entirely, causing the lake to drain within months.

The Vanishing of a Unique Dual Ecosystem

The ecological consequence of the drainage is severe. Biologists examining the water column discovered distinct microscopic communities separated by an invisible boundary just 20 centimeters thick. The upper freshwater layer hosted microorganisms, viruses, and phytoplankton entirely separate from the marine community living immediately below CBC notes.

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, says Dr. Andrew Hamilton, a co-author on the study and an Arctic oceanographer in the University of Alberta’s Department of Earth and Atmospheric Sciences.

Dr. Jérémie Bonneau and Marine Life in Milne Fiord

Researchers deployed remotely operated vehicles into the under-ice channels where freshwater drained into the fjord, uncovering a marine oasis of brittle stars, sea anemones, scallops, and other species all living in complete darkness in a channel at the base of the ice shelf Mirage News. That nutrient-rich drainage nourished marine life beneath the ice shelf, creating a complex food web that has now collapsed alongside the freshwater source.

Climate Realities in the Last Ice Area

The Milne Ice Shelf is situated within the Last Ice Area, a region expected to retain perennial sea ice longer than anywhere else in the Northern Hemisphere, and the Tuvaijuittuq Marine Protected Area, whose name means the place where the ice never melts in Inuktitut Mirage News. However, researchers emphasize that the current climate trajectory makes recovery impossible.

These systems took thousands of years to form and were lost in months, says Dr. Jérémie Bonneau, lead author on the study and now an engineering professor at Université Laval. On any human timescale, they are not coming back.

With the disappearance of the Milne Fiord epishelf lake, Canada no longer contains any active systems of this kind CBC reports. Scientists emphasize that while some ecological losses in the Arctic are gradual, the sudden drainage of Milne Fiord represents a permanent regime shift driven by unyielding temperature increases.