Air-sea CO2 fluxes along the coast of Chile: from CO2 outgassing in central northern upwelling waters to CO2 uptake in southern Patagonian fjords

Carbon system parameters measured during several expeditions along the coast of Chile (23°S–56°S) have been used to show the main spatial and temporal trends of air-sea CO₂ fluxes in the coastal waters of the eastern South Pacific. Chilean coastal waters are characterized by strong pCO₂ gradients between the atmosphere and the surface water, with high spatial and temporal variability. On average, the direction of the carbon flux changes from CO₂ outgassing at the coastal upwelling region to CO₂ sequestering at the nonupwelling fjord region in Chilean Patagonia. Estimations of surface water pCO₂ along the Patagonian fjord region showed that, while minimum pCO₂ levels (strong CO₂ undersaturation) occurs during the spring and summer period, maximum levels (including CO₂supersaturation) occur during the austral winter. CO₂ uptake in the Patagonia fjord region during spring-summer is within the order of −5 mol C m⁻² yr⁻¹, indicating a significant regional sink of atmospheric CO₂ during that season. We suggest that the CO₂ sink at Patagonia most probably exceeds the CO₂ source exerted by the coastal upwelling system off central northern Chile.