River Discharge Influences on Particulate Organic Carbon Age Structure in the Mississippi/Atchafalaya River System

Brad Rosenheim has recently published an article in the journal Global Biogeochemical Cycles which summarizes how the large Mississippi-Atchafalaya River system is involved in the carbon cycle and how this involvement changes when water levels rise.  The major analyses were performed by EES M.S. alumna, Kimberly White (née Roe) '12, using a novel technique developed by Rosenheim.  The work demonstrates that the large river system carries a significantly increased load of older carbon within the suspended load during high discharge, indicating that a decrease in the river system's efficiency in bringing recent atmospheric carbon to potentially long-term sedimentary sinks.  The river system still transports a lot more of this carbon, an important driver in anthropogenic climate change, toward sedimentary deposits during high discharge but its efficiency would be even greater without inclusion of aged carbon from older deposits in the watershed.  The approach used in this work allows river system's roles in the carbon cycle to be better defined at many time scales and provides an important first estimate of cycling processes in a large river.  In the near future, when we may ask whether building river diversions to increase our wetlands can garner carbon credits, this work will be important to obtaining an answer.


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