Air-sea exchange of nitrous oxide and methane in the Arabian Sea: A simple model of the seasonal variability

With a simple box model the seasonal variability of N2O and CH4 were simulated in surface layers in the central and western Arabian Sea. The model was able to reproduce the N2O measurements except for times when cold water filaments occur (i.e., during the SW monsoon). Based on the comparison of model results and measurements, it is concluded that the saturation of N2O in the surface layer of the Arabian Sea is mainly controlled by (i) the wind-driven air-sea exchange during the SW monsoon, (ii) entrainment of N2O from the subsurface layer, and (iii) sea surface temperature variability. However, the contribution of the factors listed above to the seasonality of the N2O saturations is different in the selected areas. The overall good agreement of model results and the majority of N2O measurements suggest that N2O formation in the surface layer of the Arabian Sea is negligible. The comparison of model's results and CH4 measurements revealed a more complex situation, partly due to considerable inconsistencies in the available CH4 data. Thus, the situation for CH4 remains unresolved and inconclusive.