Canada’s sole remaining epishelf lake, characterized by freshwater floating atop saltwater, has vanished, along with the distinctive ecosystem it sustained, as per findings in a recent study by scientists. Jérémie Bonneau, the study’s primary author and an assistant professor at Laval University in Quebec City, expressed sadness over the loss, highlighting the significance of the Milne Fiord epishelf lake on Ellesmere Island in Nunavut as the final occurrence of its kind in Canada.
The disappearance of this once common phenomenon underscores the impact of a warming climate on the Arctic. While previous reports had indicated the demise of the lake, the new study, recently featured in the journal Scientific Reports, delves into the details of its disappearance, stating that the irreversible loss represents a significant shift and the conclusion of a 4000-year era.
The formation of epishelf lakes is unique, with glaciers typically flowing into the sea along with any surface meltwater. However, the Milne Fiord’s mouth had been obstructed for millennia by the Milne Ice Shelf, preventing freshwater from entering the ocean and allowing it to accumulate above the Arctic Ocean’s saltwater. This resulted in a floating freshwater layer due to the lower density of freshwater compared to saltwater.
Moreover, the lake had been amassing freshwater for over 4,000 years, with its freshwater layer measuring 18 meters deep in 1983, akin to the height of a six-story building. Although most epishelf lakes are entirely situated atop an ice shelf, the Milne Fiord epishelf lake was connected to the ocean via an under-ice channel in the ice shelf, which had been thinning for about a century.
The lake supported two distinct ecosystems within its layers, with researchers observing minimal overlap between the freshwater and saltwater communities residing just 20 centimeters apart. The lake housed various microbes, including species not previously documented in the Arctic, creating a unique ecological balance.
Tragically, the lake met its demise in 2020 when the Milne Ice Shelf disintegrated, allowing the lake’s freshwater to drain into the ocean. The loss of the lake led to an immediate impact on the organisms living within it, as the freshwater organisms could not survive in the saltwater environment that replaced it.
While epishelf lakes have disappeared from Canada, a few still exist in Greenland and Antarctica. However, researchers warn that these ecosystems are also at risk, emphasizing the irreversible changes occurring due to climate shifts.