The atmospheric oxidation of dimethyl-sulphide (DMS) derived from marine phytoplankton is a significant source of marine sulphate aerosol. DMS has been proposed to regulate climate via changes in cloud properties, though recent studies have shown that present-day global cloud condensation nuclei (CCN) concentrations have only a weak dependence on the total emission flux of DMS. Here, we use a global aerosol microphysics model to examine how efficiently CCN are produced when DMS emissions are changed in different marine regions. We find that global CCN production per unit mass of sulphur emitted varies by more than a factor of 20 depending on where the change in oceanic DMS emission flux is applied. The variation in CCN production efficiency depends upon where CCN production processes (DMS oxidation, SO2 oxidation, nucleation and growth) are most efficient and removal processes (deposition) least efficient. The analysis shows that the production of aerosol sulphate through aqueous-phase oxidation of SO2 limits the amount of H2SO4 available for nucleation and condensational growth and therefore suppresses CCN formation, leading to the weak response of CCN to changes in DMS emission. Our results show that past and future changes in the spatial distribution of DMS emissions (through changes in the phytoplankton population or wind speed patterns) could exert a stronger control on climate than net increases in biological productivity.
展开▼
机译：源自海洋浮游植物的二甲基 - 硫化物（DMS）的大气氧化是海洋硫酸盐气溶胶的重要来源。已经提出了DMS通过云属性的变化调节气候，尽管最近的研究表明，当今全球云凝结核（CCN）浓度仅对DMS总排放通量的弱依赖性。在这里，我们使用全局气溶胶微型药物模型来检查DMS排放在不同海域的排放时如何产生CCN。我们发现，根据施加海洋DMS发射通量的变化，每单位硫磺的全球CCN生产量因施加海洋DMS排放通量的变化而变化。 CCN生产效率的变化取决于CCN生产方法（DMS氧化，SO2氧化，成核和生长）最有效和去除过程（沉积）最低效率。该分析表明，通过SO2的水相氧化产生气溶胶硫酸盐限制了可用于成核和致致生长的H 2 SO 4的量，因此抑制CCN形成，导致CCN对DMS排放变化的弱响应。我们的研究结果表明，DMS排放空间分布的过去和未来变化（通过浮游植物种群或风速模式的变化）可以对气候产生更强的控制而不是生物生产率的净增加。
展开▼
