Abstract
The ratio of N2 to Ar dissolved in seawater is an important constraint for marine N2-fixation and denitrification. This use requires, however, accurate knowledge of the influence of other processes, such as surface heating and air-sea exchange, on the distribution of these two gases. To this end, we investigated how subsurface saturation anomalies of N2 and Ar evolve from spring to autumn in the northwestern subarctic Pacific. A series of sensitivity experiments with a one-dimensional model indicate that for both gases, sea level pressure variations tend to create undersaturations, while heat flux and mixing induce supersaturation. In contrast, bubble-mediated gas exchange causes supersaturation only for N2. We show that this differential sensitivity to bubble mediated gas exchange causes the generation of N2/Ar anomalies which affect the entire seasonal evolution and thus need to be considered when using N2/Ar anomalies for constraining N2-fixation and/or denitrification.
