Biogeochemical cycles of climate-active gases CH4, N2O and DMS in Arctic and Subarctic Marine Waters

北极和亚北极海水在控制影响地球气候的各种气体的大气浓度方面发挥着重要作用。甲烷（CH4）和氧化亚氮（N2O）是使地球变暖的强效温室气体，而二甲硫化物（DMS）是一种由海洋微生物产生的微量气体，它促进云和大气气溶胶的形成，从而使进入的太阳辐射反向散射，并使地球变冷。这些“气候活性”气体的浓度和海气交换受到物理、化学和生物过程相互作用的影响，对气候驱动的海洋条件变化很敏感。目前，这些潜在的气候依赖性变化的幅度很难受到直接观测的限制。拟议的研究计划将收集海洋表层水中DMS、CH4和N2O浓度和生物/化学循环的基本数据。主要研究目标是：1)在一系列海洋条件下量化北极和亚北极海域这些气体的时空变化；2)利用同位素标记实验量化DMS、CH4和N2O循环的关键产耗速率。这项工作的结果将促进我们对未来几十年海洋产生这些气体的潜在气候依赖变化的理解。******基于船舶的实地调查将用于绘制亚北极太平洋沿海和近海水域以及加拿大北冰洋的CH4、N2O和DMS浓度图。测量将使用我们在过去十年中开发的一套分析方法进行。同位素标记实验将通过各种途径跟踪DMS的生产和消耗，量化不同前体化合物对CH4和N2O的循环。本文的研究结果将为了解海洋CH4、N2O和DMS浓度的调节因子及其对气候敏感变量的潜在响应提供新的机制见解。这反过来又将对理解全球气候系统的未来演变具有重大意义。* * * * *

Arctic and Subarctic marine waters play a large role in controlling the atmospheric concentration of various gases that influence Earth's climate. Methane (CH4) and nitrous oxide (N2O) are potent greenhouse gases acting to warm the planet, while dimethylsulfide (DMS), a trace gas produced by marine microbes, promotes the formation of clouds and atmospheric aerosols that back-scatter incoming solar radiation and act to cool the planet. The concentration and sea-air exchange of these 'climate-active' gases are influenced through the interplay of physical, chemical and biological processes, and sensitive to climate-driven shifts in oceanic conditions. At present, the magnitude of these potential climate-dependent changes is poorly constrained by direct observations. The proposed research program will collect fundamental data on the concentrations and biological / chemical cycles of DMS, CH4 and N2O in surface ocean waters. The principle research objectives are to: 1) quantify the spatial and temporal variability of these gases in Arctic and Subarctic marine waters across a range of oceanographic conditions; and 2) use isotope-labeling experiments to quantify the rates of key production and consumption in the DMS, CH4 and N2O cycles. The results from this work will advance our understanding of potential climate-dependent changes in the oceanic production of these gases over the coming decades. ******Ship-based field surveys will be used to map the concentrations of CH4, N2O and DMS in coastal and offshore waters of the Subarctic Pacific, and in the Canadian Arctic Ocean. Measurements will be conducted using a suite of analytical methods we have developed over the past decade. Isotope labeling experiments will be used to follow the production and consumption of DMS through various pathways, and quantify the cycling of CH4 and N2O through different precursor compounds. The results of the proposed work will provide new mechanistic insight into the factors regulating oceanic CH4, N2O and DMS concentrations, and their potential response to climate-sensitive variables. This, in turn, will be of great relevance to understanding the future evolution of the global climate system. *****