Abstract:

The sea-to-air flux of marine biological dimethylsulfuide (DMS) can have an effect on cloud condensation and regional solar radiation, hence reducing the global surface temperature. Meanwhile, the DMS flux influence on climate cooling is more obvious because of a large quantity of melting ice in the polar region. This paper studied the distributions and annual variations of wind speed (WIND), cloud cover (CLOUD), sea surface temperatures (SST), chlorophyll (CHL), and mixed layer depth (MLD) in the Subantarctic nearly ice-free region (South Australia) (40°S—60°S, 110°E—140°E) for the years 2012—2014. A genetic algorithm technique was used to calibrate the main parameters in the DMS model. Simulation and analysis of the sea-air flux was also conducted. Finally, we used the CMIP5 (5th Coupled Model Intercomparison Project) to predict changes in the DMS flux for 4×CO2 (year 2100), compared with 1×CO2 (the contemporary case for the years 2012—2014). The results show that the increased rates of 4×CO2 for SST, CLOUD, and WIND were 0.9, 5.6, and 12.3%, respectively. However, the MLD reduced rate was 41.0% and the increased rate of transfer velocity (kw) was 58.8%. Because of the distinction of the melting ice, the DMS flux increased by only 9.4%. Therefore, the increased rate of the DMS flux is far less than the Polar Regions. The research results show that DMS has less effect on the greenhouse conditions in the Subantarctic nearly ice-free region (South Australia).

Key words: Subantarctic, Dimethylsulfide (DMS), DMS sea-air flux, genetic algorithms, Chlorophyll (CHL)