Coasts containing frozen soil called permafrost make up about one third of the Earth's total coastline, and as these melt in the Arctic under global warming, large quantities of carbon dioxide is being released into the atmosphere, according to a study.
The researchers, including those from GFZ Helmholtz Centre Potsdam in Germany, simulated the effects of permafrost erosion in a lab experiment to find out how much carbon is released into the atmosphere along eroding Arctic coasts.
They collected permafrost samples from Herschel Island off the northern coast of the Yukon in northwest Canada, and mixed them with seawater from offshore.
The research team took periodic measurements of greenhouse gases this mixture emitted over the course of four months -- the average length of open-water season in the Arctic.
The results of the study, published in the journal Geophysical Research Letters, revealed that carbon dioxide was released as rapidly from thawing permafrost in seawater as it is from thawing permafrost on land.
"Our research found that the erosion of permafrost coastlines can lead to the rapid release of significant quantities of carbon dioxide, which can be expected to increase as coastal erosion accelerates, temperatures increase, sea ice diminishes, and stronger storms batter Arctic coasts," said George Tanski, lead author of the study from Vrije Universiteit Amsterdam in the Netherlands.
While earlier research showed that thawing permafrost on land caused significant releases of greenhouse gases, the current study indicated that eroding coasts and nearshore waters were also significant sources of carbon dioxide emissions.
The study, according to the researchers, questions the long held role of coastal zones as a main point of passage for carbon from land to sea, neglecting how in these regions carbon is also transported into the atmosphere.
"Carbon budgets and climate simulations have so far missed coastal erosion in their equations even though it might be a substantial source of carbon dioxide," Tanski said.
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