Influence of terrestrial inputs on continental shelf carbon dioxide.

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 re- moving pCO₂ variations due to the annual temperature cycle and air-sea gas ex- change 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 off-shore. 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 CO₂ distribution. [ABSTRACT FROM AUTHOR]