OTTAWA (dpa-AFX) - Runoff from one of North America's largest rivers is driving intense carbon dioxide emissions in the Arctic Ocean, a reecnt study reveales.
It has been estimated that the cold waters of the Arctic absorb as much as 180 million metric tons of carbon per year - more than three times what New York City emits annually - making it one of Earth's critical carbon sinks. But recent findings show that thawing permafrost and carbon-rich runoff from Canada's Mackenzie River trigger part of the Arctic Ocean to release more carbon dioxide than it absorbs.
The study explores how scientists are using state-of-the-art computer modeling to study rivers such as the Mackenzie, which flows into a region of the Arctic Ocean called the Beaufort Sea. Like many parts of the Arctic, the Mackenzie River and its delta have faced significantly warmer temperatures in recent years across all seasons, leading to more melting and thawing of waterways and landscapes.
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 researchers from the U.S., France, and Canada found that the river discharge was triggering such intense outgassing in the southeastern Beaufort Sea that it tipped the carbon balance, leading to a net CO2 release of 0.13 million metric tons per year. This is roughly equivalent to the annual emissions from 28,000 gasoline-powered cars. The release of CO2 into the atmosphere varied between seasons, being more pronounced in warmer months, when river discharge was high and there was less sea ice to cover and trap the gas.
'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.
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.
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