Canada loses its final epishelf lake ecosystem

Canada's last documented epishelf lake has vanished following the collapse of a surrounding ice shelf in Nunavut, ending a four-thousand-year-old polar habitat. According to findings published in Scientific Reports, the unique reservoir at Milne Fjord emptied completely into the ocean after the Milne Ice Shelf fractured in 2020.

Epishelf lakes form when coastal glacial shelves trap liquid meltwater above heavier seawater. This unusual stratification previously allowed both freshwater organisms and saltwater species to survive together within separate vertical zones. Earlier underwater surveys had even recorded fish, brittle stars, and sea anemones thriving in deep darkness beneath the floating ice, nourished by outflow from the lake.

Researchers from Carleton University and the University of Alberta had monitored the site since 2011 using automated sensor moorings. Field data collected in 2022 confirmed that the ten-meter freshwater cap drained away within several months after roughly half of the ice shelf broke free. Scientists noted that the lost ecosystem will not recover on any realistic human timeline.

The collapse stemmed from a combination of elevated air and sea temperatures during exceptionally warm summers in 2019 and 2020. Melting caused channels to carve into the shelf, while warm marine waters degraded the structure from below and open waves pounded the exposed outer edge. Ellesmere Island was historically bordered by up to seventeen similar lakes during the twentieth century, but warming has progressively eliminated them.

The fjord sits within the Arctic's Last Ice Area, an expanse long expected to preserve perennial sea ice against rising global temperatures. Although parts of the broader sector were protected in 2019 through the Tuvaijuittuk Marine Protected Area to safeguard ice-dependent animals such as ringed seals and polar bears, recent climate projections indicate the territory remains increasingly susceptible to seasonal melting.