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

在这个项目中，一名参加2015年美国地理痕迹北极考察的调查员将对北冰洋中的甲烷、一种溶解的痕量气体以及溶解的痕量元素镓、钡和钒进行测量。与国际地质勘测计划中的其他多国倡议一样，美国北极探险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通量，并确定这些分布对不断变化的环境条件的敏感性。一些微量元素对生命是必不可少的，另一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而测量的痕量元素和气体将被用作各种过程的示踪剂，例如输入北冰洋的河流和大气以及该区域的环流。从该项目中获得的知识和经验将被纳入海洋学和海洋化学课程，并通过公共宣传活动加以分享。该项目将支持研究生的科学培训。作为这项研究的一部分，将测量的示踪剂甲烷、镓、钡和钒将提供有关海洋环流和北极水输入的重要信息。镓可能被证明是北冰洋西部大西洋和太平洋水组分的灵敏示踪剂，这是环流研究中感兴趣的问题，也与北冰洋大陆架上甲烷水合物的稳定性预测有关。之所以感兴趣，是因为它已被证明是河流输入和对盐跃层的贡献的指示器。这与理解北极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，北极陆架面积的很大比例使其成为研究陆架沉积物吸收是否决定表层海洋钒消耗的理想区域。至于甲烷，北极水域是这种温室气体向大气排放的重要来源，全球变化可能会加剧其释放。因此，确定甲烷分布本身将是有意义的，尽管它也是与大陆架相互作用以及河流输入的潜在有价值的指标。总体而言，这项研究的结果将有助于加深对关键的海洋生物地球化学和物理过程的了解，包括跨边界的物质交换、北冰洋的水源以及甲烷进入大气的通量。

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.