Influence of terrestrial inputs on continental shelf carbon dioxide

[摘要] The US South Atlantic Bight (SAB) is a low-latitudeshallow continental shelf bordered landward by abundant salt marshes andrivers. Based on previously published data on sea surface partial pressureof carbon dioxide (pCO₂) and new dissolved inorganic carbon (DIC) anddissolved organic carbon (DOC) data, a model analysis is presented toidentify and quantify the contributions of various terrestrial carbon inputson SAB sea surface pCO₂. After removal of pCO₂ variations due toannual temperature variability and air–sea gas exchange from the in situpCO₂, the temperature- and gas-exchange-corrected pCO₂ (TG-correctedpCO₂) is derived. Contributions from rivers, salt marshes, and thecontinental shelf to the TG-corrected pCO₂ are then calculated. Ourfindings demonstrate that although additions of CO₂ from within shelf waters (i.e., ΔpCO₂(shelf)) were thegreatest of the three components and underwent the largest seasonal changes,ΔpCO₂(shelf) showed smaller onshore–offshore gradients thanrivers and marshes. In contrast, CO₂ contributions from river (ΔpCO₂(river)) and salt marsh (ΔpCO₂(marsh)) components weregreatest closest to the coast and decreased with distance offshore. Inaddition, the magnitude of ΔpCO₂(marsh) was about three-foldgreater than ΔpCO₂(river). Our findings also revealed thatdecomposition of terrestrial organic carbon was an important factorregulating the seasonal pattern of pCO₂ on the inner shelf. Despitelarge uncertainties, this study demonstrates the importance of terrestrialinputs, in particular those from coastal wetlands, on coastal ocean CO₂distributions.

[学科分类] 地球化学与岩石