GEOTRACES Arctic Section: Methane, vanadium, barium, and gallium as process indicators in the Arctic Ocean

在这个项目中，参加2015年美国GEOTRACES北极考察队的一名研究人员将测量北冰洋中溶解的微量气体甲烷，以及溶解的微量元素镓、钡和钒。与国际地质足迹计划中的其他多国倡议一样，美国北极考察的目标是确定控制海洋中关键微量元素和同位素分布的过程和量化通量，并确定这些分布对不断变化的环境条件的敏感性。有些微量元素是生命所必需的，有些是已知的生物毒素，还有一些很重要，因为它们可以用作海洋中各种物理、化学和生物过程的示踪剂。作为该项目的一部分，测量的微量元素和气体将被用作各种过程的示踪剂，如河流和大气输入到北冰洋，以及该地区的环流。从这个项目中获得的知识和经验将纳入海洋学和海洋化学课程，并通过公共宣传活动进行分享。该项目将支持一名研究生的科学训练。作为这项研究的一部分，要测量的示踪剂是甲烷、镓、钡和钒，它们将提供有关海洋环流和北极水输入的重要信息。镓很可能被证明是北冰洋西部大西洋和太平洋水成分的敏感示踪剂，这是环流研究中感兴趣的问题，也与北极大陆架上甲烷水合物稳定性的预测有关。钡之所以引起人们的兴趣，是因为它已被证明是河流输入和对盐斜的贡献的一个指标。这与了解北极的上层海洋环流以及淡水对大西洋经向翻转环流的贡献有关。对于钒而言，北极大陆架面积的很大比例使其成为研究大陆架沉积物吸收是否决定海洋表面钒消耗的理想区域。就甲烷而言，北极水域是大气中这种温室气体的重要来源，全球变化可能会加剧甲烷的释放。因此，确定甲烷的分布本身就很有意义，尽管它也是与大陆架和河流输入相互作用的潜在有价值的指标。总的来说，这项研究的结果将增加对关键海洋生物地球化学和物理过程的了解，包括物质的跨边界交换、北冰洋的水源和甲烷到大气的通量。

In this project, an investigator participating in the 2015 U.S. GEOTRACES Arctic expedition will make measurements of methane, a dissolved trace gas, as well as the dissolved trace elements of gallium, barium, and vanadium in the Arctic Ocean. In common with other multinational initiatives in the International GEOTRACES Program, the goals of the U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Some trace elements are essential to life, others are known biological toxins, and still others are important because they can be used as tracers of a variety of physical, chemical, and biological processes in the sea. The trace elements and gas measured as part of this project will be used as tracers for a variety of processes such as river and atmospheric inputs to the Arctic Ocean, as well as circulation in the region. The knowledge and experience gained from this project will be incorporated into courses in oceanography and marine chemistry, as well as be shared through public outreach activities. The project will support the scientific training of a graduate student.The tracers to be measured as part of this study, methane, gallium, barium, and vanadium, will provide important information about oceanic circulation and water inputs to the Arctic. Gallium is likely to prove a sensitive tracer for Atlantic versus Pacific water components in the western Arctic Ocean, an issue of interest in circulation studies and also relevant to projections of the stability of methane hydrates on the Arctic shelves. Barium is of interest because it has been shown to be an indicator of fluvial inputs and contributions to the halocline. This is pertinent to understanding upper ocean circulation in the Arctic as well as to freshwater contributions to the Atlantic Meridional Overturning Circulation. For vanadium, the large proportion of shelf area in the Arctic makes this an ideal region to examine whether shelf sediment uptake determines surface ocean vanadium depletion. For methane, Arctic waters are a significant source of this Greenhouse Gas to the atmosphere and global change is likely exacerbating its release. Determination of the methane distribution will therefore be of interest in and of itself, although it is also a potentially valuable indicator of interactions with the shelf as well as of river inputs. Overall, results from this study will lead to an increased understanding of key ocean biogeochemical and physical processes including cross margin exchange of materials, sources of water in the Arctic Ocean, and fluxes of methane to the atmosphere.