Biological carbon uptake and trace gas emissions in the polar oceans under a changing climate

南北半球的高纬度海洋在控制大气中气候活跃的痕量气体浓度方面发挥了很大作用。这些区域对海洋二氧化碳吸收的贡献不成比例，并展示了大量二甲基硫化物(DMS)的海-气通量，DMS是一种生物成因气体，影响云的形成和大气辐射收支。全球模拟研究表明，极地海洋的二氧化碳和DMS循环可能在未来一个世纪发生重大变化，以应对海冰覆盖、环流模式和生物生产力随气候变化的情况。然而，这些与气候有关的潜在变化的大小很难受到直接观测的限制。拟议的研究计划将收集有关南极和北极海域生物碳循环的基础数据，以及各种气候活性气体(如二甲基硫、甲烷和一氧化二氮)的产生。主要研究目标是：1)检查海洋表面温度和二氧化碳浓度上升对南极和北极海洋初级生产力和浮游植物物种组成的影响；2)量化各种水文和海冰条件下北极和南极冰川生物氧饱和度、二氧化碳和二甲基硫浓度的时空变异性；3)利用同位素示踪实验，量化高纬度海洋生态系统循环中的关键生产和消费项目；4)测量与地表水生产力和海冰覆盖有关的北极陆架水域甲烷(CH4)和一氧化二氮(N2O)浓度和生产率。将利用现场调查绘制南大洋和北冰洋痕量气体的表面分布图，使用膜进样质谱仪(MIMS)进行高空间分辨率分析，并结合GC-MS对离散深度剖面样本进行高灵敏度分析。使用13C和2H标记化合物的同位素示踪实验将用于通过各种代谢途径跟踪二甲基硫的生产和消费，而浮游植物对温度和二氧化碳变异性的敏感性将通过受控的野外培养实验进行评估。

The high latitude oceans of both the Northern and Southern hemispheres play a large role in controlling atmospheric concentrations of climate-active trace gases. These regions contribute disproportionately to oceanic CO2 uptake and exhibit large sea-air fluxes of dimethylsulfide (DMS), a biogenic gas which influences cloud formation and impacts the atmospheric radiation budget. Global modeling studies suggest that polar ocean CO2 and DMS cycles are likely to change significantly over the coming century in response to climate-dependent changes in sea ice cover, circulation patterns and biological productivity. However, the magnitude of these potential climate-dependent changes is very poorly constrained by direct observations. The proposed research program will collect fundamental data on biological carbon cycling in Antarctic and Arctic marine waters, and on the production of various climate-active gases (e.g. DMS, methane and nitrous oxide). The principle research objectives are to: 1) examine the influence of increasing sea surface temperature and pCO2 on primary productivity and phytoplankton species assemblage composition in Antarctic and Arctic marine waters; 2) quantify the spatial and temporal variability of biological oxygen saturation, pCO2 and DMS concentrations in Arctic and Antarctic polynyas over a range of hydrographic and sea ice conditions; 3) use isotope tracer experiments to quantify key production and consumption terms in the high latitude DMS cycle, and 4) measure methane (CH4) and nitrous oxide (N2O) concentrations and production rates in Arctic shelf waters in relation to surface water productivity and sea ice cover. Field surveys will be used to map the surface distribution of trace gases in the Southern Ocean and Arctic Ocean using membrane inlet mass spectrometry (MIMS) for high spatial resolution analysis, combined with GC-MS for high sensitivity analysis of discrete depth profile samples. Isotope tracer experiments using 13C and 2H labelled compounds will be used to follow the production and consumption of DMS through various metabolic pathways, while phytoplankton sensitivity to temperature and CO2 variability will be assessed using controlled field-based incubation experiments.