A new study has confirmed what researchers feared since the breakup of the Milne Ice Shelf in 2020: Canada’s last epishelf lake, a freshwater lake dammed by an ice shelf, has disappeared. Based on a decade of ocean measurements, satellite images and field observations collected before and after the breakup, scientists have reconstructed the lake’s disappearance. Canada’s far north lies in the Arctic Circle and serves as one of the region’s last refuges for summer sea ice and ice-dependent wildlife such as polar bears, ringed seals and Atlantic walruses. In the local Inuktitut language, these protected areas on northern Ellesmere Island in Nunavut are known as Tuvaijuittuq, “the place where the ice never melts.” Only the ice is melting. The recent loss of the Milne Fiord epishelf lake, an ancient ecosystem and the last of its kind in Canada, has shown that even this ice refuge that once seemed permanent is vulnerable to rapid changes associated with climate warming. It may seem freezing, but temperatures in the Canadian Arctic are rising rapidly. Credit: Derek Mueller In late August, a study published in Scientific Reports by a team of researchers from the University of British Columbia (UBC), the University of Alberta, Universite Laval, and Carleton University brought together many different lines of evidence and showed that Lake Epishelf began draining as soon as the Milne Ice Shelf broke up in July 2020. By fall 2020, Lake Epishelf and the unique ecosystem it supported were largely gone. “The ice shelf and lake had been thinning for decades, but the 2020 breakup was the last straw. The lake dried up within months,” said the study’s lead author, Jérémie Bonneau, who conducted some of the research during his PhD at UBC. An epishelf lake forms when an ice shelf acts as a dam, trapping a layer of freshwater that floats on top of seawater connected to the ocean. These types of lakes create multi-story habitats that allow marine and freshwater wildlife to coexist within the same water column. The last ice-dammed lake in Canada is gone, gone forever, researchers say. Credit: Adrienne White The first field measurements collected after the breakup in 2020 showed that, by July 2022, brackish water had completely replaced the lake’s distinctive freshwater layer. Since then, annual monitoring has shown no signs of recovery, suggesting the lake is gone forever. “Epishelf lakes can indicate when an ice shelf is under pressure, and that’s what we saw here,” said co-author Bernard Laval. “The data showed that the ice shelf was failing. Once the ice is gone, the ecosystem is gone with it. There is no turning back.” Studying dynamic systems like these in one of the most remote parts of the world is no easy task. To get to Milne Fiord, researchers had to take several flights to Ottawa, Iqaluit and then to Resolute Bay, via Arctic Bay. At Resolute Bay, they spent several days at the Federal Continental Polar Shelf Program Base, preparing equipment before a small plane, known as the Twin Otter, took them the rest of the way. Once there, the researchers placed thermos-sized sensor tubes, which recorded temperature, depth and conductivity, which they used to determine the salt content of the water. These instruments were left in place during the COVID-canceled 2020 field season and could not be recovered until two years later. Laval recovering a mooring in a pond on the Milne Ice Shelf. Credit: Bella Mouchet “We saw the [Milne Ice Shelf] “The instruments were there, watching. We just couldn’t reach them.” The study found that fresh water entering Milne Fiord is now being dumped directly into the ocean, as the remaining ice shelf can no longer contain it. For the lake to be restored, the ice shelf would have to recover, something researchers say is impossible given the current climate trajectory. “These systems took thousands of years to form and were lost within months,” Bonneau said. “On any human time scale, they’re not coming back.” You can read more about the study published in Scientific Reports here. Featured image: When the Milne Ice Shelf fractured, it exposed freshwater channels that were once protected beneath the surface. Credit: Cameron Fitzpatrick More stories from around the world
