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

北方和南半球的高纬度海洋在控制气候活性痕量气体的大气浓度方面发挥着重要作用。这些地区对海洋二氧化碳吸收的贡献不成比例，并表现出大量的二甲基硫（DMS），一种影响云的形成和影响大气辐射收支的生物气体的海气通量。全球模拟研究表明，在未来世纪，极地海洋CO2和DMS循环可能会因海冰覆盖、环流模式和生物生产力的气候变化而发生重大变化。然而，这些潜在的依赖气候的变化的规模是非常不受直接观测。拟议的研究方案将收集关于南极和北极海洋沃茨生物碳循环的基本数据，以及关于各种气候活跃气体（如二甲基硫醚、甲烷和一氧化二氮）产生的基本数据。主要研究目标是：1）研究海表温度和pCO 2升高对南极和北极海洋沃茨初级生产力和浮游植物物种组合组成的影响; 2）定量分析不同水文和海冰条件下北极和南极冰间冰藻生物氧饱和度、pCO 2和DMS浓度的时空变化; 3）使用同位素示踪实验来量化高纬度二甲基硫醚循环中的关键生产和消费条件，以及4）测量北极大陆架沃茨中甲烷（CH 4）和一氧化二氮（N2 O）的浓度和生产率与地表水生产力和海冰覆盖的关系。将利用实地调查绘制南大洋和北冰洋微量气体的表面分布图，采用膜式进气质谱法进行高空间分辨率分析，并结合气相色谱-质谱法对离散深度剖面样本进行高灵敏度分析。使用13 C和2 H标记化合物的同位素示踪实验将用于跟踪DMS通过各种代谢途径的生产和消费，而浮游植物对温度和CO2变化的敏感性将使用受控的实地培养实验进行评估。

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.