Wind-driven lateral variations of partial pressure of carbon dioxide in a large estuary

Abstract

Abstract Estuarine carbon cycle and biogeochemical studies usually focus on along-estuary variations and neglect cross-estuary variations. In a stratified middle reach of the Chesapeake Bay, we observed a counterclockwise circulation and upwelling of subsurface water with high partial pressure of carbon dioxide (pCO2) on the eastern shoal during a down-estuary wind event from October 24 to 25, 2013. The average air-sea CO2 gas exchange flux over the eastern one-third of this cross transect was approximately 20 to 40% higher, while the flux over the western 1/3 was lower by a similar amount, compared with the middle section. A statistically strong correlation between pCO2 and salinity values was observed, suggesting the presence of a high CO2 source from the higher salinity bottom water. The observations suggest that wind-driven lateral upwelling can enhance the release of respired CO2 from subsurface water in stratified large estuaries by as much as 30% over a short time-scale of hours.