北冰洋海冰消融对二甲基硫化物循环和DMS海气释放的影响

气候变暖背景下，由于北冰洋海冰消融明显及其对海气间物质交换、浮游植物动态变化的链条式影响，预计北冰洋负温室效应气体二甲基硫（DMS）的海气释放强度将显著增加，从而有可能缓解北冰洋气候变暖。本研究根据西北冰洋表层二甲基硫化物浓度和DMS海气通量逐年升高的前期研究结果，推测其主要驱动力是海冰消融引起的季节性无冰区范围扩大。本项目以西北冰洋和北冰洋中心区为研究海域，通过现场观测、室外模拟实验、室内培养实验和历史数据分析，探明夏季海冰消融过程中二甲基硫化物浓度及其周转的变化特征，剖析冰缘线区域二甲基硫化物的主要来源，明确十年内季节性无冰区范围变化对DMS海气通量的影响程度及原因，揭示冰缘线融冰、夏季融冰和年际融冰过程中二甲基硫化物周转积累和DMS海气释放的变化规律和驱动因素，阐明海水二甲基硫化物循环对海冰消融的响应过程及其潜在的气候效应，为深入研究北冰洋对全球生态效应、气候变化的反馈提供科学依据。

The Arctic is warming faster than any other region in the world. Among the changes already witnessed, the loss of seasonal sea ice is by far the most striking. The expansion of the ice-free surface area in the Arctic Ocean could stimulate oceanic emissions of dimethylsulphide (DMS) - a climate-relevant trace gas generated by ice algae and phytoplankton, potentially cooling the Arctic climate. Our preliminary observations demonstrated that summer DMS fluxes and surface concentration of dimethylated sulfur compounds increased sharply from 2012 to 2014 in the Western Arctic Ocean. Our working hypothesis is that, the expansion of the ice-free surface area as seasonal sea-ice cover recedes, will increase the production of dimethylated sulfur compounds and DMS sea-to-air emission in the Arctic. Impact of Arctic meltdown on the cycling of dimethylated sulfur compounds and the emission of DMS in the Western Arctic Ocean and Central Arctic Ocean will be studied in this research project by various methods, including field observation, ice-algae culture, simulation experiments and historical data analysis. This research project will investigate temporal evolution of DMSP cycling rates and the biochemical factors which control the turnover of DMS from DMSP and DMSO during the summer melt period, assess phytoplankton and DMS dynamics and sources of high dimethylated sulfur compounds at ice edges, determine the biogeochemical characteristics of biogenic sulfur and interannual variations of DMS sea-to-air flux in the progressively expanding seasonal ice-free zone, and evaluate how the ongoing reduction of seasonal sea-ice cover and increased ice melt will affect the strength of dimethylated sulfur compounds sources and DMS sea-air exchange under global warming scenarios. The resulting data will greatly advance our understanding of the key processes governing DMS production in and around the sea ice, of the sensitivity of these processes to projected changes in the Arctic environment, and of how global warming and rapid sea ice retreat affects the sink and source of Arctic dimethylated sulfur compounds, with a focus on biological and physical processes in the Arctic Ocean.