Canada’s sole remaining epishelf lake, characterized by freshwater floating atop saltwater, has vanished, along with the distinctive ecosystem it sustained, according to a recent study. Jérémie Bonneau, the study’s lead author and an assistant professor at Laval University in Quebec City, expressed sorrow over the loss of the Milne Fiord epishelf lake on Ellesmere Island in Nunavut, emphasizing that it was the final occurrence of its kind in Canada. The disappearance of this unique feature underscores the impact of a warming climate on the Arctic.
Although the demise of the lake had been previously documented, the latest study, recently published in the journal Scientific Reports, provides a detailed account of the lake’s disappearance, describing it as an irreversible loss that signifies a significant shift in the ecosystem after a 4000-year era came to an end.
Epishelf lakes form due to glaciers, which typically release meltwater into the sea. In the case of the Milne Fiord, the mouth of the fiord had been obstructed for millennia by the Milne Ice Shelf, preventing freshwater from mixing with the ocean water. This led to the accumulation of freshwater on top of the Arctic Ocean’s saltwater, creating a distinctive floating layer due to the lower density of freshwater compared to saltwater. The lake was shielded by a layer of ice year-round, preserving the separation of the freshwater and saltwater layers.
The Milne Fiord epishelf lake had been accumulating freshwater for over 4,000 years, with its freshwater layer measuring 18 meters deep when first measured in 1983. Despite being an epishelf lake connected to the ocean through an under-ice channel in the ice shelf, the lake’s thinning ice shelf contributed to its eventual disappearance.
The lake’s unique ecosystem, characterized by distinct communities of bacteria, viruses, and phytoplankton in the freshwater and saltwater layers, highlighted the remarkable biodiversity within the lake. The disappearance of the lake following the collapse of the Milne Ice Shelf in 2020 led to the immediate demise of the freshwater organisms, as the saltwater fiord replaced the once isolated freshwater environment.
While epishelf lakes have vanished from Canada, a few such lakes still exist in Greenland and Antarctica. Scientists warn that these ecosystems are at risk, emphasizing the urgent need to address climate change to preserve Earth’s diverse natural wonders.