In this marshy corner of Canada’s Northwest Territories, the continent’s second largest river system ends a thousand-mile journey that begins near Alberta. Along the way, the river acts as a conveyor belt for mineral nutrients as well as organic and inorganic matter. That material drains into the Beaufort Sea as a soup of dissolved carbon and sediment. Some of the carbon is eventually released, or outgassed, into the atmosphere by natural processes.
Scientists have thought of the southeastern Beaufort Sea as a weak-to-moderate CO2 sink, meaning it absorbs more of the greenhouse gas than it releases. But there has been great uncertainty due to a lack of data from the remote region.
To fill that void, the study team adapted a global ocean biogeochemical model called ECCO-Darwin, which was developed at NASA’s Jet Propulsion Laboratory in Southern California and the Massachusetts Institute of Technology in Cambridge. The model assimilates nearly all available ocean observations collected for more than two decades by sea- and satellite-based instruments (sea level observations from the Jason-series altimeters, for example, and ocean-bottom pressure from the GRACE and GRACE Follow-On missions).
The scientists used the model to simulate the discharge of fresh water and the elements and compounds it carries – including carbon, nitrogen, and silica – across nearly 20 years (from 2000 to 2019).
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Scientists have for decades studied how carbon cycles between the open ocean and atmosphere, a process called air-sea CO2 flux. However, the observational record is sparse along the coastal fringes of the Arctic, where the terrain, sea ice, and long polar nights can make long-term monitoring and experiments challenging.
“With our model, we are trying to explore the real contribution of the coastal peripheries and rivers to the Arctic carbon cycle,” said lead author Clément Bertin, a scientist at Littoral Environnement et Sociétés in France.
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