Imagine a lake the size of Alberta's Wabamun Lake draining away in just a few months, taking its dependent ecosystem down with it, never to return.
It's similar to what happened to a lake in Ellesmere Island's Milne Fiord in Nunavut in 2020, according to a new study published in Scientific Reports.
The "epishelf" lake was formed when the Milne Ice Sheet created a dam at the mouth of the fjord, trapping a layer of freshwater over the Arctic ocean water below.
Six years ago, that ice shelf broke apart, and the water drained into the ocean - a direct consequence of warming temperatures, says Dr. Andrew Hamilton, an Arctic oceanographer in the University of Alberta's Department of Earth and Atmospheric Sciences.
"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," says Hamilton, a co-author on the study.
"When the ice shelf broke apart, that unique ecological structure disappeared. It was the last of its kind in Canada."
The study is the first complete reconstruction of the lake's drainage and its transformation from a freshwater ecosystem into a marine environment. Although scientists knew the ice sheet had collapsed in 2020, it took another two or three years to determine what happened to the lake, partly because of the cancelled field season due to COVID in 2020.
Dr. Derek Mueller, a professor of geography and environmental studies at Carleton University, established the research program that tracked the ice shelf and lake through years of accelerating change.
"The ice shelf and lake had been thinning for decades, but the 2020 breakup was the last straw," adds co-author Dr. Jérémie Bonneau, a professor of civil and water engineering at Université Laval. "The lake drained within months."
The interdisciplinary team from the U of A, the University of British Columbia, Laval and Carleton have been monitoring changes in the ice sheet since 2011, when Hamilton first set up a "mooring" of sensors and other instruments to record changes in the temperature and salt content of the fjord.
"Many of the ice shelves along northern Ellesmere Island had broken up before we began the research program," says Hamilton. "Some of my colleagues had recorded the loss of other epishelf lakes in other fjords prior to that time. The Milne Fiord was unique in that it was the last intact system. It had a fully integral ice shelf that spanned the entire width of the fiord, and a deep epishelf lake."
In addition to Hamilton's oceanographic mooring, the team also used annual water profiles, satellite imagery and field observations.
Hamilton describes the lost ecosystem as "phenomenal." In 2017, the team drilled into the lake's outflow channel below the ice shelf and were "astounded by what was there," says Hamilton, who captured the exploration on video.
"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."
That ecosystem has vanished, and it is now impossible for the ice shelf that contained it to recover under the current climate trajectory, say the study's authors.
The Milne Ice Shelf lies within the Last Ice Area, a region expected to retain perennial sea ice longer than anywhere else in the Northern Hemisphere. It is also part of the Tuvaijuittuq Marine Protected Area, whose name means "the place where the ice never melts" in Inuktitut.
"These systems took thousands of years to form and were lost in months," says Bonneau. "On any human timescale, they are not coming back."
Hamilton calls the warming trend in the region "inevitable."
"We're not going to be able to prevent some of these changes, and some result in extinction events like this one, where there is no turning back. The best we can do as humanity and society is limit their extent by acting now.
"My kids are never going to see that kind of ice shelf and lake system in their lifetime. It's the end of an era."
