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Carbon dissolved in rivers is damaging our planet

Two new studies are improving our understanding of the ways in which carbon is transferred between the land, ocean, and atmosphere in the Arctic. By taking into account how carbon reaches the ocean via rivers, these studies cover a significant gap in previous research, which has largely focused on how carbon passes from land into the atmosphere through burning fossil fuels, forest fires, leaking methane gas, or emissions from melting permafrost.

“There’s been a lot of research that has looked at the vertical flow of carbon from land to the atmosphere,” said study lead author Michael Rawlins, a professor of Geoscience at the University of Massachusetts Amherst and the associate director of the Climate System Research Center. “Far less attention has been paid to how carbon is transferred from land to the ocean via rivers.”

As rivers and streams flow over the land, they collect carbon and carry it towards the seas or oceans. While a small amount of this “dissolved organic carbon” (DOC) evaporates into the atmosphere as greenhouse gas, most of it flows into the ocean, where it becomes a significant part of coastal food webs. 

In order to better understand this ocean-ward, lateral flows of carbon in the Arctic, Professor Rawlins and his team have modified a numerical method that captures the annual accumulation of snow and the freezing and thawing of soils, by adding a comprehensive account of the production, storage, decomposition, and loading of DOC into streams and rivers.

By employing this model, researchers found rising amounts of freshwater and DOC exported to a lagoon in Northern Alaska. In 2019, the freshwater export of DOC was three times the amount exported in the 1980s. 

“Increased freshwater export has implications for salinity and other components of the lagoon aquatic environment,” explained Rawlins. “The largest freshwater and DOC increases occur in Autumn, which is not surprising given the significant losses in sea ice across the nearby Beaufort and Chukchi Seas, in turn connected to our warming climate.”

This new model can help scientists to better understand the complex ways in which climate change is altering the Earth’s carbon cycle, and provide new research directions about how the negative effects of global warming could be mitigated. 

The studies are published in the Journal of Geophysical Research and Environmental Research Letters.

By Andrei Ionescu, Staff Writer

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