All Earth’s water contains naturally occurring organic molecules, from dissolved sugars to the decay products of more complex plant polymers and other biomolecules. And all carbon entering surface waters, whether from soils and vegetation, must pass through and interact with the dissolved organic carbon (DOC) pool as it is respired to CO2 and released to the atmosphere, or transformed to other forms of carbon. Dr. Rose Cory, an assistant professor in the Department of Environmental Sciences and Engineering at the University of North Carolina at Chapel Hill, studies how the chemistry of dissolved organic carbon (DOC) controls how and how fast it can be returned to the atmosphere as CO2 by sunlight and microbes.
Cory works in the Arctic where climate change is progressing rapidly thawing permafrost that contain nearly half of the world’s soil organic carbon. When permafrost thaws, frozen soil carbon becomes accessible to decomposition by bacteria and fungi. These organisms respire defrosted carbon to methane or carbon dioxide and release it to the atmosphere. Conversion of this currently frozen carbon pool to greenhouse gases has the potential to double the amount of CO2 in the atmosphere on a timescale that is similar to human inputs. New research on the North Slope of Alaska is showing that permafrost soils are not “thawing quietly” in place. Instead, thawing of ground ice is causing massive land-surface subsidence called “thermokarst failures”. These catastrophic failures release ancient carbon and bacteria that have been frozen for thousands of years, and thus are hotspots for conversion of organic carbon to CO2. Cory investigates specifically how sunlight affects DOC and in turn controls the transformation and fate of DOC as it moves from land to water. Cory finds that exposure to sunlight accelerates the return of this DOC to the atmosphere as CO2, which may further increase the rate of global warming. Because climate change is influencing our planet’s evolution, understanding the fate of newly released carbon will help predict our future and thus benefit society.