Methane in the northern Atlantic controlled by microbial oxidation and atmospheric history

During May - August, 1997, the distributions of dissolved methane and CCl3F (CFC11) were measured in the Atlantic between 50 degrees and 60 degrees N. In surface waters throughout the region, methane was observed to be close to equilibrium with the atmospheric mixing ratio, implying that surface oce an methane is tracking its atmospheric history in regions of North Atlantic Deep Water formation. Despite the different atmospheric history and ocean chemistry of CH4 and CFC11, their spatial distribution patterns in the wate r column are remarkably similar. One-dimensional distributions have been si mulated with an advection-diffusion model forced by the atmospheric histori es. The results suggest that the similar patterns result from the increasin g input of CH4 and CFC11 to newly formed deep waters over time, combined wi th the effect of horizontal mixing and the oxidation of methane on a 50 yea r time scale.