Factors controlling pCO2 variability in the eastern Gulf of Cádiz (SW Iberian Península).

Spatiotemporal variations of the partial pressure of CO₂ (pCO₂) were studied during 8 oceanographic cruises conducted between March 2014 and February 2016 in surface waters of the eastern shelf of the Gulf of Cádiz (SW Iberian Península) between the Guadalquivir River and Cape Trafalgar. pCO₂ presented a range of variation between 320.6 and 513.6 µatm, with highest values during summer and autumn and lowest during spring and winter, showing a linear dependence between pCO₂ and temperature. The distributions of pCO₂ were not homogeneous. Spatially, there was a general decrease from coastal to off-shore stations associated with continental inputs and presented an increase in the zones deeper than 400 m due to the influence of the eastward branch of the Azores Current. On the other side, the study area acted as source of CO₂ to the atmosphere during summer and autumn and as a sink in spring and winter, with a mean value for the study period of −0.18 ± 1.32 mmol m⁻² d⁻¹. In the Guadalquivir and Sancti Petri sections, the CO₂ fluxes decreased towards offshore, whereas in the Trafalgar section increased due to the presence of an upwelling. These results highlighted the Gulf of Cádiz as a CO₂ sink, with a capture capacity of 14.9 Gg year⁻¹. [ABSTRACT FROM AUTHOR]