Canada's Last Arctic Epishelf Lake Is Gone Forever and It's Not Coming Back

A One-of-a-Kind Ecosystem Erased in Months

A lake that had survived for thousands of years in the Canadian Arctic is now gone. A new study published in the journal Scientific Reports has confirmed what scientists feared: Canada's last epishelf lake drained into the Arctic Ocean following the 2020 breakup of the Milne Ice Shelf and will not recover. The loss marks the end of a geological and ecological era — one that took millennia to build and just months to destroy.

Epishelf lakes form when an ice shelf acts as a dam, trapping a layer of freshwater floating above seawater connected to the ocean. "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," said Andrew Hamilton, an arctic oceanographer at the University of Alberta and a co-author of the study. "When the ice shelf broke apart, that unique ecological structure disappeared. It was the last of its kind in Canada."

How the Collapse Unfolded

In July 2020, the Milne Ice Shelf broke apart, losing 45 per cent of its area and removing the barrier that held the freshwater in place. The speed of the collapse was staggering. The ice shelf, which had been thinning for decades due to warming Arctic temperatures, lost approximately 45 percent of its surface area in just two days. Findings show that the freshwater layer began escaping immediately after the collapse and had mostly vanished by autumn 2020.

Within two months of the ice shelf breaking up, the freshwater had drained and none was left in the fiord. The first field measurements collected after the breakup showed that by July 2022, brackish water had fully replaced the lake's distinct freshwater layer. Annual monitoring since then has found no sign of recovery. The lead researcher put it plainly: "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, a professor of civil and water engineering at Université Laval.

What Was Lost Beneath the Ice

The Milne Fiord epishelf lake, located on northern Ellesmere Island in Nunavut, supported freshwater microorganisms near the surface and marine species below. When researchers drilled into the lake's outflow channel in 2017, they were stunned by what they found. "We found a robust marine ecosystem with brittle stars, sea anemones, scallops, etc., all living in complete darkness in a channel at the base of the ice shelf." Freshwater organisms living there would have died more or less instantly when mixed with seawater.

Within months, the freshwater layer drained into the Arctic Ocean, effectively ending a 4,000-year-old ecological era. The scale of that loss is difficult to overstate. As lead author Bonneau said, "These systems took thousands of years to form and were lost in months. On any human timescale, they are not coming back."

A Warning Sign the Arctic Is Sending

Bonneau noted that the complete disappearance of a once common phenomenon shows how a warming climate is transforming the Arctic. "Epishelf lakes can signal when an ice shelf is under stress, and that's what we saw here," said co-author Dr. Bernard Laval, a professor of civil engineering at UBC who leads its environmental fluid mechanics research group. The Milne Fiord lake wasn't just a curiosity — it was a canary in the coal mine, and that canary is now silent.

Researchers say the loss of the epishelf lake cannot simply be reversed. For the lake to return, the ice shelf would need to rebuild itself and recreate the barrier that once separated freshwater from seawater. Under current climate trajectories, that is not a realistic prospect. The disappearance of Milne Fiord's lake is a stark reminder that some things lost to climate change don't come back on any timeline that matters to human civilization — and that the Arctic is changing faster than even scientists expected.