| Available from UMI in association with The British Library.; Dimethylsulphide (DMS) (CH{dollar}sb3)sb2{dollar}S is one of many sulphur species originating from the Earth's biota. Its importance with respect to the global sulphur cycle is that it had previously been proposed that sulphur dioxide formed the major part of sea-to-air sulphur transfer despite the insufficient quantities of hydrogen sulphide detected. As non-sea-salt sulphate aerosols form the majority of cloud condensation nuclei over the Earth's ocean, this imbalance in the understanding of the sulphur cycle has massive implications for not only biogeochemistry but also for global change. Charlson et al. (1987) proposed that the production and effects of DMS constitutes a feedback loop and that "although we do not understand the details of the climatic feedback, it seems that cloud condensation nuclei form biogenic DMS currently act to cool the Earth" (Charlson et al., 1987).; In this thesis, which concentrates upon the climatic response to such a feedback mechanism, the combination of a biogeochemical boxmodel, population biology models and an energy balance model (E.B.M.) has been used to describe this feedback loop. The model produced is very simple and as a result, as it is unsuitable for prediction, illustrates the basic features of the system. A variety of population biology models have been used separately to illustrate the effect of different parameterizations of the DMS-producing phytoplankton on the model results. In conclusion, this model indicates that the DMS feedback loop may operate to ameliorate the Earth's climate (the feedback may have the effect of warming the poles and cooling the equator) as well as providing a mechanism which contributes to the sulphur cycle.; Due to the lack of available data with which to test the E.B.M., a geographic information system (G.I.S.) has been used to examine the relationships between various components of the DMS feedback loop. The data, in the form of maps of relevant variables, has been digitized for three marine areas (Mediterranean, Indian ocean and the Mid-Atlantic). The results, in the form of manipulated maps to provide more suitable data, data to indicate the relationship between variables and maps of possible DMS production, are presented. The two techniques used show that although data on the occurrence of DMS in the environment is limited it is possible to provide tentative conclusions concerning feasible areas of further study. |
