A rare freshwater-saltwater ecosystem in Canada's Arctic has disappeared following the collapse of the Milne Ice Shelf. Researchers from three universities confirmed the loss of a 4,000-year-old phenomenon on Ellesmere Island.
The 18-meter freshwater layer of Milne Fiord
For four millennia, the Milne Ice Shelf on Ellesmere Island acted as a massive frozen dam, trapping glacial meltwater to create a rare epishelf lake. According to the report, this unique structure consisted of an 18-meter-deep layer of freshwater that floated directly atop the salty waters of the ocean. This delicate balance was maintained by an ice cover ranging from 50 to 100 centimeters in thickness, which prevented wind from mixing the two distinct layers.
Data collected by researchers from Laval University, the University of Alberta, and Carleton University shows that this freshwater column remained stable from the 1980s until 2019. However, as the report indicates, the entire system was suddenly drained in 2020 once the Milne Ice Shelf fractured, effectively erasing the last remaining epishelf lake in Canada.
Distinct microbial taxa separated by 20 centimeters
The collapse of the Milne Ice Shelf allowed scientists to analyze a biological boundary that had been hidden for thousands of years. DNA sequencing revealed that the freshwater upper layer and the saltwater below hosted entirely different biological communities, despite being separated by a gap of only 20 centimeters. The freshwater habitat contained microbial species and benthic bacteria that had never previously been documented in the Arctic region.
Beyond the microbes, the researchers utilized a remotely operated vehicle (ROV) to explore sub-ice channels. The ROV documented a thriving community of sea stars, scallops,and ghostly sea anemones living in depths that are typically devoid of food. These organisms survived by feeding on nutrients that surged upward when the freshwater from the Milne Fiord lake rushed into the ocean during the shelf's collapse.
A global pattern of ice shelf breakup
The disappearance of the Milne Fiord ecosystem is not an isolated incident but part of a broader, accelerating trend of Arctic transformation. The study's authors note that similar ice shelf breakups are occurring worldwide, driven by climate warming. This specific loss represents a "regime shift," where the fundamental environmental conditions of the Canadian Arctic are changing in ways that may be irreversible.
This pattern echoes the wider instability seen across polar regions, where the loss of floating ice shelves removes critical buffers for land-based glaciers. As these shelves vanih, the rate of glacial melt into the sea often accelerates, further altering the salinity and temperature of coastal waters and disrupting the habitats of species adapted to these precise conditions.
The downstream effects on Arctic marine food webs
While the immediate biological census of the Milne Fiord is complete, several critical questions remain regarding the long-term ecological fallout.. It is currently unknown how the sudden injection of 4,000 years of trapped freshwater and nutrients will alter the local marine food web over the next decade. Additionally, the report does not specify how the loss of this specific ice shelf will impact the flow and stability of the glaciers that previously fed the lake.
The researchers emphasize a pressing need for continuous monitoring of meltwater pathways and ice shelf integrity across the Arctic. Without this data, scientists cannot fully anticipate which other unique habitats are on the brink of collapse or how to mitigate the resulting loss of biodiversity.
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