Seasonal air–sea CO2 fluxes in the southern California Current off the Baja California Peninsula (Mexico)

Abstract

Seasonal climatology of air–sea CO₂ exchange was estimated from in situ sea surface CO₂ partial pressure, temperature, salinity, and satellite wind data obtained from 2004 to 2011 in the southern region of the California Current, off the Baja California Peninsula (Mexico). The average annual CO₂ flux indicates that the study area is a source of CO₂ to the atmosphere (0.65 mmol m^–2 d^–1). It changes from being a source in summer (2.33 mmol m^–2 d^–1) and autumn (0.92 mmol m^–2 d^–1) to acting as a sink in winter (–0.26 mmol m^–2 d^–1) and spring (–0.37 mmol m^–2 d^–1). The area to the north of latitud 28ºN (off Punta Eugenia) is a CO₂ sink (–0.42 mmol m^–2 d^–1), whereas the area to the south of this latitude is a source of CO₂ to the atmosphere (1.80 mmol m^–2 d^–1), mostly due to thermodynamic effects. The northern coastal zone is a permanent CO₂ sink (–1.29 mmol m^–2 d^–1). During the 2004 El Niño event the whole area contributed 2.00 mmol m^–2 d^–1 of CO₂ to the atmosphere, but during the 2011 La Niña the ocean absorbed 5.30 mmol m^–2 d^–1 as a result of physical and biological dynamics. The seasonalcycle is dominated by temperature rather than biological effects, except in the northern coastal area. It is necessary to continue with in situ measurements of the CO₂ system to have solid foundations to estimate the effect of the long-term increase in dissolved inorganic carbon onmarine organisms.