A lake near Sachs Harbour has drained after a section of permafrost surrounding it gave way, government officials suspect.
Angus Lake was a popular fishing spot near the community. But over the course of June, it drained rapidly and is now a large crater.
"The lake was named after my dad, Angus Elias," said Angus Irvin Elias. "When I seen the video, it was heartbreaking, probably just because it was named after him."
Satellite imagery of the lake shows it quickly losing water after surface ice thawed in June. A image taken on June 30 shows the lake nearly full, but by July 4 the lake looks half empty. By July 7 it is nearly completely empty.
A spokesperson for Industry, Tourism and Investment confirmed the most likely cause of the lake draining out was permafrost degradation.
"The terrain in the photo looks like polygonal terrain. When this type of terrain degrades, ponds can form that increase permafrost degradation and potentially creating channels for water to flow," said ITI communications officer Wesley Cook. "In this case, the result was enough of a change in the terrain for water to flow out of the lake an into the Sachs River until the lake was drained.
"We donSA国际影视传媒檛 know what the long-term effects of the lake drainage will be at this time," Cook added.
Angus Lake near Sachs Harbour is not to be confused with the Angus Lake in the North Slave region, which is an unrelated body of water.
Residents of Sachs Harbour lamented the loss of the nearby lake.
Veronica Dezelak moved to Aklavik with her husband Trevor in 2018. The pair owned a tent on the lakeside SA国际影视传媒� a popular stopover for hunters, fishers and other travellers on Banks Island.
Dezelak said the lake was a popular place to swim and was large enough to boat in. But now it's been reduced to two ponds.
"Even in the winter, people would stop at the tent to warm up," she said. "It was used by many people to warm up and for goose hunting. Kids used to go swim there. We drank from the lake too.
"We saw the lake gone within a week."
Northwest Territories Geological Survey permafrost geohazard scientist Ashley Rudy said water that is sitting on or flowing over permafrost terrain can speed up thawing. When ice wedges in tundra polygons break down, they can direct water flow, causing more erosion. If a lake starts draining through a break in its side, it can rapidly melt frozen ground, leading to fast erosion and turning the lake into a crater in a short time.
"Permafrost is variable in the amount of ice it has," she said. "In certain years, you can have ponds sitting on the landscape (without degrading permafrost), but if you combine that with a wet year or a lot of melting snow increasing water levels, it's more water that can flow and accelerate degradation."
While a channel remains the most likely cause of Angus Lake's demise, it's not the only way a lake can drain in the North.
Rudy noted lake levels in the NWT have been trending lower overall, in part, due to drier conditions. In the High Arctic, lakes sit on top of permafrost which can also slowly degrade beneath them. In some cases, the permafrost thaws enough that it begins to absorb the water above it and the lake seeps into groundwater.
Thaw slumps can also create openings that will drain a lake in short order. But, as so many lakes in the North are remote and out of the public eye, Rudy added it's difficult to say how often sudden changes similar to Angus Lake are happening.
"Some of the research shows that water levels are going down quicker than had first been expected due to climate change, however, these catastrophic lake drainage events, there's not a lot of evidence that those have increased in frequency," she said. "This was a lake that was used by the community. Using satellite imagery, you'll see lakes which have drained, but you don't always know the time in which they drained.
"There's not a predictive tool to say which lakes are more susceptible to drainage at this moment," Rudy added.
While she said she would miss the lake, Dezelak said she was trying to remain optimistic.
She noted that the lake's sandy bottom could be used for other things.
"I feel it would be really fun for a dirt bike," she said. "There's two dirt bikes in the community SA国际影视传媒� the lake's the perfect spot now. It's all sand. It's beautiful."
