Modeling p CO 2 variability in the Gulf of Mexico

Abstract

A three-dimensional coupled physical–biogeochemical model was used to simulate and examine temporal and spatial variability of surface p CO 2 in the Gulf of Mexico (GoM). The model is driven by realistic atmospheric forcing, open boundary conditions from a data-assimilative global ocean circulation model, and observed freshwater and terrestrial nutrient and carbon input from major rivers. A seven-year model hindcast (2004–2010) was performed and was validated against in situ measurements. The model revealed clear seasonality in surface p CO 2. Based on the multi-year mean of the model results, the GoM is an overall CO 2 sink with a flux of 1.34 × 10 12 mol C yr −1, which, together with the enormous fluvial carbon input, is balanced by the carbon export through the Loop Current. A sensitivity experiment was performed where all biological sources and sinks of carbon were disabled. In this simulation surface p CO 2 was elevated by ~ 70 ppm, providing the evidence that biological uptake is a primary driver for the observed CO 2 sink. The model also provided insights about factors influencing the spatial distribution of surface p CO 2 and sources of uncertainty in the carbon budget.