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Crew looks for clues on coastline erosion on Beaufort Sea floor

For some, it was another research voyage. But for Lisa Broder, it was a once-in-a-lifetime opportunity.
The route of the CCGS Amundsen this last September. To avoid exposure to Covid-19, the crew did not make landfall during the month-long voyage. Photo courtesy of PeCaBeau 2021

For some, it was another research voyage. But for Lisa Broder, it was a once-in-a-lifetime opportunity.

Resuming its annual trek through the Northwest Passage, the CCGS Amundsen set out from Resolute Bay early September and made its way towards Inuvialuit Settlement Region waters. Carrying 36 researchers from around the world, the ship was manned by a crew of 24 for the month-long mission.

“For us, this was an amazing opportunity,” said Broder, who led the expedition. “Many of us have worked in Canada and in the North before, but none of us have been on this ship. It was a great opportunity to come here and see this first-hand.”

“The general objective has to do with thawing permafrost, both on land and the sub-sea. We just want to see where all those eroding coastlines and the Mackenzie River plume goes and what happens to that material in the ocean.

“It can have a large impact on the coastal community and marine ecosystem, but also on a global scale. We have a diverse team of scientists on board with their own objectives.”

Broder was one of several European Union scientists who was along for the trip for the first time. Historically, the missions have been mainly funded by Canada, but this time around the E.U. helped with the bill.

Examining how thawing permafrost affects the water table, Broder said team was examining the environment from multiple angles, cross referencing data collected from water samples with satellite imagery and other sources of information.

When permafrost thaws, run-off carries the soil into the river systems. Those rivers carry the sediment further down, eventually discharging it into the Beaufort Sea. The amount of sediment discharged is so large it can be seen from space. In fact, scientists can analyze the colour of the water in satellite imagery and determine how much sediment is floating in the water table.

Carbon- and nitrogen-rich sediments in the water column produce a surge in nutrients serves as a great feast for microscopic organisms such as phytoplankton and algae, but limit the amount of sunlight that can penetrate the water, which affects breeding. One focus of Broder’s research is how much degradation is occurring in organic substances.

Change is coming to the Arctic at a rapid pace — the coastline along the Beaufort Sea is among the fastest transforming coastlines in the world, eroding away at a rate of 40 metres per year in some areas, notably Kelly Island, located near Richard’s Island.

“What’s neat about this cruise is it is taking the accumulation of all the erosion,” Natural Resources Canada (NRCan) physical scientist Dustin Whalen said. “We can’t really identify a source such as Kelly Island, but we’re hopeful to identify the total amount of erosion altogether.”

Broder said traces of coastal erosion have been tracked as far out as 24 kilometres out to sea, though the distance it could travel depended on wind, current and a number of other factors.

Drilling into the past

To understand what lies in the future for the Beaufort Sea, researchers need to understand its history. Fortunately, all the sediment flowing into the ocean eventually settles at the bottom, where it is buried by more sediment flowing in. Over time, the buried sediments are compacted into layers, which can be distinguished by the environmental factors that surrounded the sediment at the time it was deposited.

With this knowledge in mind, scientists can drill out core samples showing a cross-section of each layer. From the differences in the chemistry of each layer of sediment, researchers can then determine a slew of environmental factors present when the soil was first deposited, including water temperature, salinity and nutrient content, going back thousands of years.

Broder added scientists were able to determine ocean conditions as far back as the last ice age, when ocean levels were up to 120 metres lower in much of the world and the coastline of the Arctic ocean extended much further out. She noted the amount of soil that could be bored out depended on a number of conditions.

“We’re happy if we get five metres of sediment,” she said. “Depending on where you are in the Beaufort Sea, that can correspond to a thousand, maybe two thousand years, or it can go back to the last ice age and beyond.

“Depending on how much sediment you get per year or per thousand years, that corresponds to how far you can look back in time.”


Mapping the ocean floor

A third mission on the CCGS Amundsen this fall was a cartographic effort — taking higher quality images of the Arctic sea floor.

The Arctic Ocean is notable for its continental shelves — shallow tracts of land that was above sea level during the ice age. In fact, 53 per cent of the ocean’s surface area consists of shelf.

Whalen said determining how that shelf transitions to the seafloor is a big focus of the research.

“The mapping component just adds another component to where we want to look for these samples,” he said. “In some cases, we’re looking for areas where the sediment coming from the coast is going to get trapped — if we don’t see small little basins or areas where sediment can sink in, we’ll move on.

“That way, when we put in the larger instruments, we’re maximizing their potential.”

Broder added the mapping process also was able to determine the contents of the underlying sediment, also showing where to drill.

To map the floor, sonar is used to bounce sounds off the ocean floor. Faster the signal returns to the ship, the closer the bottom. With this, scientists are able to create a 3-Dimensional map of the Arctic Ocean.

While the mission was focused on the Beaufort Sea in the ISR, the CCGS Amudsen did not drop anchor, instead returning to its origin at Resolute Bay.

Though he noted he would have liked to have visited his friends on the mainland, having had to miss his trip to the Arctic last year, Whalen noted it was good to be back in his element and tasting the Arctic air.

“It’s real nice to get out in field,” he said. “Even though it’s not the usual location, it’s still good to be back out in the ISR finally.”

About the Author: Eric Bowling

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