Washington : According to a NASA study, intense carbon dioxide (CO2) emissions are being driven by an increasingly warming Arctic Ocean, which was once thought to be one of Earth’s critical carbon sinks.
Up to 180 million metric tonnes of carbon dioxide are thought to be absorbed annually by the icy waters of the Arctic, which is more than three times the amount of carbon dioxide that New York City emits annually.
However, the study revealed that a portion of the Arctic Ocean releases more CO2 than it takes in due to thawing permafrost and carbon-rich runoff from Canada’s Mackenzie River.
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 Clement Bertin, a scientist at Littoral Environnement et Societes in France.
Such insights are critical because about half of the area of the Arctic Ocean is composed of coastal waters, where land meets sea in a complex embrace. And while the study focused on a particular corner of the Arctic Ocean, it can help tell a larger story of environmental change unfolding in the region.
Using 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 study explored the Mackenzie rivers, which flows into a region of the Arctic Ocean called the Beaufort Sea.
The model incorporates almost all of the ocean observations that have been gathered over the course of more than 20 years by satellite and sea-based instruments. Throughout a nearly 20-year period (from 2000 to 2019), the scientists used the model to simulate the discharge of fresh water and the elements and compounds it carries, such as carbon, nitrogen, and silica.
Researchers from France, the US, and Canada discovered that the river discharge was causing the southeastern Beaufort Sea to experience such intense outgassing that it tipped the carbon balance, resulting in a net annual release of 0.13 million metric tonnes of CO2—roughly the same amount of emissions produced annually by 28,000 gasoline-powered cars.
Seasonal variations in river discharge and the absence of sea ice to trap and conceal the gas caused a greater release of CO2 into the atmosphere during warmer months. According to scientists, the Arctic has warmed at least three times as quickly as any other place on Earth since the 1970s, changing its waters and ecosystems.
While some of these modifications encourage the region to release more CO2, others cause the region to absorb more CO2.
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