The region may have experienced one of the worst floods ever recorded.
A University of Alberta-led international team was studying the ancient Glacial Lake Agassiz which occupied around 1.5 million square kilometres of what is now southern Manitoba and central Saskatchewan.
It formed after the 3 km thick Laurentide Ice Shield atop the northern half of North America began to melt about 16,000 years ago.
The team was able to determine through geomorphological evidence that the lake began to spill out around 4,000 years later.
The floodwaters are believed to have traveled along the Clearwater-Athabasca channel, which is where Fort McMurray is located, connecting with the Mackenzie River Basin before emptying out in the Arctic Ocean.
“We know that a large discharge has gone through the area but the rate of the discharge or the magnitude was pretty much unknown,” Sophie Norris, study-lead and former U of A PhD student in the Faculty of Science.
They ended up creating a model of a gradual dam failure to try and determine how much water was spilling out per second.
Through the model, they were able to estimate the flood’s peak discharge rate was around two million cubic metres of water every second which would make it one of the largest floods in the planet’s history.
To put into context, all the water in the great lakes would be gone in roughly nine months at this rate.
“What I find deeply satisfying is that modern hydraulic modelling, when applied to the evidence preserved in the landscape, shows how a phenomenal flood propagated 12,000 years ago,” added Paul Carling, study co-author from the University of Southampton, United Kingdom.
“When all the uncertainties are considered, the outcome remains pretty solid.”
The team also believes there’s a possibility this flood may have caused an ice age or at least extend it.
They determined the event happened around the same time as Younger Dryas, the most recent glacial epoch. During this time, the northern hemisphere returned to glacial conditions for hundreds of years before the last ice age, which lived on for roughly 100,000 years, ended.
“We don’t know for sure that the flood caused the Earth to slip back into the ice age, but certainly if you put that much water into the Arctic Ocean, the models show you get cooling of the northern hemisphere climate,” said Duane Froese, Norris’s PhD supervisor and Canada Research Chair in Northern Environmental Change in the Department of Earth and Atmospheric Sciences.
Moving forward, the team plans on researching whether this catastrophic discharge happened at the start of the cold reversal and whether it may have been the main cause or played a part in a series of different events.
