Scientists have estimated that the Arctic Ocean absorbs as much as 180 million metric tons of carbon every year – making it one of Earth’s most important carbon sinks. Now, a new study shows that thawing permafrost and carbon-rich runoff from Canada’s Mackenzie river is causing a part of the Arctic Ocean to release more carbon than it can absorb.
The study examines the use of state-of-the-art computer modelling to study rivers such as the Mackenzie, which flows into a region of the Arctic Ocean called the Beaufort Sea, US space agency Nasa explains in a press statement.
Similar to how many regions of the Arctic are experiencing the effects of global warming, the Mackenzie river and its delta have faced significantly warmer temperatures in recent years, which has caused melting and thawing of waterways and landscapes.
For this study, the researchers used 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. Using this model, the researchers simulated the discharge of fresh water and the elements in it such as carbon, nitrogen, and silica – from 2000 to 2019.
The researchers found that carbon dioxide discharge by Mackenzie river was triggering significant outgassing in the southeastern Beaufort Sea. This tipped the carbon balance, leading to a net carbon dioxide release of 0.13 million metric tons per year, the statement explained. This is almost equivalent to the annual emissions from 28,000 gasoline-powered cars. The release of carbon dioxide was more during warmer months, when river discharge was high and there was less sea ice to absorb the gas, the statement adds.
According to Nasa, such findings are important as half of the area of the Arctic Ocean is made of coastal waters, where land meets sea. While the study focused on one region, it can help better understand the environmental changes occurring in the ocean.
"With our model, we are trying to explore the real contribution of the coastal peripheries and rivers to the Arctic carbon cycle,” lead author Clément Bertin said in the statement.