Role of wind stress and heat fluxes in generating interannual-to-decadal variability of air-sea CO₂ and O₂ fluxes in
a North Atlantic model
A coupled ecosystem–circulation model of the North Atlantic is used to examine the individual contributions by wind stress and surface heat fluxes to naturally driven interannual–to–decadal variability of air–sea fluxes of CO₂ and O₂ during 1948–2002. The model results indicate that variations in O₂ fluxes are mainly driven by variations in surface heat fluxes in the extratropics (15ºN to 70ºN), and by wind stress in the tropics (10ºS to 15ºN). Conversely, variations in simulated CO₂ fluxes are predominantly wind–stress driven over the entire model domain (18ºS to 70ºN); while variability in piston velocity and surface heat fluxes is less important. The simulated uptake of O₂ by the North Atlantic amounts to 70 ± 11 Tmol/yr to which the subpolar region (45ºN to 70ºN) contributes by 62 ± 10 Tmol/yr. Whereas the subpolar North Atlantic takes up more than 2/3 of the total carbon absorbed by the North Atlantic in our model (about 0.3 Pg C/yr), interannual variability of air–sea CO₂ fluxes reaches similar values (about 0.01 Pg C/yr each) in the subpolar (45ºN to 70ºN), the subtropical (15ºN to 45ºN) and the equatorial (10ºS to 15ºN) Atlantic.