Highlights
• The pCO2 and salinity were repeatedly measured in the cross-channel section.
• Down-estuary winds drove the upwelling of high-salinity subsurface water.
• Higher pCO2 values were observed on the eastern than those on the western shoal.
• Air-sea CO2 exchange fluxes were 20–40% higher on the eastern shoal.
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.
Huang W.-J., Cai W.-J., Xie X. & Li M., in press. Wind-driven lateral variations of partial pressure of carbon dioxide in a large estuary. Journal of Marine Systems. Article (subscription required).
