Air-Sea CO2 Fluxes in the Gulf of Mexico, a Data-Based Climatology

As is the case for many marginal seas, carbon measurements in the Gulf of Mexico were sparse both spatially and temporally before 2006. However, the unique bio-geographical features of the Gulf, including inflow of waters with higher alkalinity and inorganic carbon from the 10^th largest river in the world, the Mississippi River warrant determination of the total air-sea CO₂ flux and its contribution to the North American carbon balance. Within the frame of the Gulf of Mexico Coastal Carbon Synthesis effort and the NASA ROSES “Air-Sea CO₂ Flux and Carbon Budget Synthesis and Modeling in the Entire Gulf of Mexico” proposal, work has been carried out to compile and provide the most comprehensive set of surface and water column ocean carbon measurements available in the region. Building upon the surface pCO₂ data contained in SOCAT, additional data for surface pCO₂ in the region has been obtained. The dataset contains over 500K surface measurements, of which approximately 1/3 are currently not in the SOCAT or CDIAC holdings but are in the process of being submitted to both. Based on this new dataset, the Gulf is a weak sink for CO₂ on an annual scale and presents two distinct behaviors, corresponding to a dry (CO₂ sink) and a wet (CO₂ source) season. An equivalent dataset containing pCO₂, TA, pH and DIC in the water column has been compiled and will be used to create algorithms for the creation of fields of saturation state.