Development, intercomparison and evaluation of an improved mechanism for the oxidation of dimethyl sulfide

Abstract

Dimethyl sulfide (DMS) is an important trace gas emitted from the ocean. The oxidation of DMS is important for global climate through the role DMS plays in setting the sulfate aerosol background in the troposphere. However, the mechanisms of DMS oxidation are very complex and have proved elusive to accurately determine in spite of decades of research. As a result the representation of DMS oxidation in global chemistry-climate models is often greatly simplified. Recent field observations and laboratory studies have prompted renewed efforts in constraining the uncertainty in the oxidation mechanism of DMS as incorporated in global chemistry-climate models. Here we build on recent laboratory and observational evidence and develop a new DMS mechanism for inclusion in the UKCA chemistry-climate model. We compare our new mechanism to the existing UKCA mechanism and to a range of recently developed mechanisms reported in the literature through a series of global and box model experiments. Our box model experiments highlight that there is significant variance in simulated secondary oxidation products of DMS across mechanisms used in the literature, with divergence in the sensitivity of these products to temperature exhibited. Our global model studies show that our updated and improved DMS scheme performs better than the current scheme when compared against observations. However, sensitivity studies underscore the need for further laboratory and observational constraints.