Influence of terrestrial inputs on continental shelf carbon dioxide
1Department of Marine Sciences, The University of Georgia, Athens, Georgia 30602, USA
2Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Columbus, Ohio 43212, USA
*current address: Cooperative Institute for Climate and Satellites, Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
Abstract. Air-sea carbon dioxide (CO2) fluxes have recently been reported for the US South Atlantic Bight (SAB), a low-latitude shallow continental shelf bordered landward by abundant salt marshes and rivers. In this study, influences of terrestrial inputs on sea surface partial pressure of CO2 (pCO2) in the SAB are quantified. After removing pCO2 variations due to the annual temperature cycle and air-sea gas exchange from the in situ pCO2, temperature and gas exchange corrected (TG-corrected) pCO2 is derived. Contributions from the river, marsh, and continental shelf to the TG-corrected pCO2 are then calculated. Findings show that CO2 contributions from the river [ΔpCO2(river)] are highest close to the coast and decrease with distance offshore. For example, ΔpCO2(river) was up to 30 μatm on the inner shelf but averaged only 0–3 μatm on the outer shelf during January and March 2005. CO2 contributions from salt marshes [ΔpCO2(marsh)] show similar spatial and seasonal distributions as ΔpCO2(river), with the magnitude of ΔpCO2(marsh) being about three times as high as that of ΔpCO2(river). CO2 contributions from within the shelf [ΔpCO2(shelf)] are highest among the three components. Compared to ΔpCO2(river) and ΔpCO2(marsh), ΔpCO2(shelf) show the smallest onshore-offshore gradients. Despite large uncertainties, this study clearly demonstrates the importance of terrestrial impacts on coastal ocean CO2distribution.