Modeling pCO2 Variability in the Gulf of Mexico

Friday, 19 December 2014
Z. George Xue1, Ruoying He2, Katja Fennel3, Wei-Jun Cai4, Steven E Lohrenz5, Wei-Jen Huang4 and Hanqin Tian6, (1)Louisiana State University, Baton Rouge, LA, United States, (2)North Carolina State Univ., Raleigh, NC, United States, (3)Dalhousie University, Halifax, NS, Canada, (4)University of Delaware, Newark, DE, United States, (5)University of Massachusetts Dartmouth, New Bedford, MA, United States, (6)Auburn University at Montgomery, Auburn, AL, United States
A three-dimensional coupled physical-biogeochemical model was used to simulate and examine temporal and spatial variability of surface pCO2 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 pCO2. Based on the multi-year mean of the model results, the GoM is an overall CO2 sink with a flux of 1.34 × 1012 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 pCO2 was elevated by ~70 ppm, providing the evidence that biological uptake is a primary driver for the observed CO2 sink. The model also provided insights about factors influencing the spatial distribution of surface pCO2 and sources of uncertainty in the carbon budget.