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Abstract
Dimethylsulfide (DMS), carbon monoxide (CO), carbonyl sulfide (COS), and carbon disulfide (CS2) are trace gases produced in the upper ocean and outgassed into the marine atmosphere. DMS is the main source of reduced sulfur to the remote marine troposphere where it is oxidized to sulfate particles on time scales of a few days. The flux of DMS from the oceans is of interest to atmospheric modellers, but there have been no global fields of sea surface DMS concentration upon which to base a flux estimate. Part of the goal of the present work has been to assemble a global database of all existing DMS measurements and to use an interpolation scheme to create a series of monthly fields of sea surface DMS concentration. The results suggest that there is pronounced seasonality of DMS concentration at high latitudes with a maximum in the summer months. DMS concentration seems to be linked to phytoplankton blooms at high latitudes, but the correlation with chlorophyll concentration is low.
COS, CS2, and CO are produced by photochemical reactions in the upper ocean and are lost by biological and chemical processes and also by surface outgassing. The concentrations of the species can be simulated in a physical model taking account of the source and sink terms in addition to dilution processes. Upper ocean mixing processes are not completely understood and have been parameterized using several models. The source and sink terms of the photochemical species are not well-constrained by incubation measurements but can be determined approximately by running the coupled models in an inverse mode. A method is proposed wherein the global oceanic flux of the species may be determined.
