Collaborative Research: US GEOTRACES Arctic Section - Water mass composition, circulation and mean residence times derived from measurements of natural and manmade tracers

在这个项目中，参加2015年美国地理轨迹北极探险队的调查人员将测量六个海洋示踪器，以更好地了解北冰洋的海水运动。有了这些信息，其他研究人员将更容易解释他们自己的海水化学数据。与国际地质勘测计划中的其他国家倡议一样，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。作为这项研究的一部分，将测量的示踪剂已经证明了它们在研究短到长时间尺度上的水团组成、循环和平均停留时间方面的价值。该项目还将为两名高中教师提供培训，并为高中生制定课程。北极目前正在以全球其他地方未曾见过的速度发生系统规模的环境变化。因此，必须确定微量元素和同位素分布的基线，以供今后参考，并开始了解决定北冰洋微量元素和同位素分布的过程。尤其是在海冰正在消退的情况下，必须了解气候指标如何影响北极系统的重要功能，如初级生产力，或者更广泛地说，在这些快速变化的环境条件下影响碳的循环。为了进一步了解水的运动以及北极地区的痕量元素分布，这组研究人员将测量横断面上的氯氟烃(CFCs)、六氟化硫(SF6)、氚、氦同位素、水的稳定同位素和C-14。在过去的研究中，这些示踪剂被成功地用于确定水的质量组成、循环路径和平均停留时间，时间范围从不到一年(CFCs/SF6和氚/He-3)到几百年(C-14)。研究人员计划对邮轮航道沿线部分和全部冰盖水域中CFCs和SF6的饱和度进行测量，并将计算所有站点位置的正向和反向海冰轨迹，以确定海冰样本的来源。这些轨迹将被用作了解表面混合层中水的路径的第一步。

In this project, investigators participating in the 2015 U.S. GEOTRACES Arctic expedition will measure six oceanic tracers in order to better understand oceanic water movement in the Arctic Ocean. With this information in-hand, it will be much easier for other investigators to interpret their own seawater chemistry data. In common with other national 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 tracers to be measured as part of this study have proven their value for studies of water mass composition, circulation, and mean residence times on short to long time scales. This project will also provide training for two high school teachers, and develop curriculum for high school students.The Arctic is presently undergoing system-scale environmental change at a pace not seen elsewhere on the globe. Thus, it is essential to establish a baseline of the distributions of trace elements and isotopes (TEIs) for future reference and to begin understanding the processes that determine the TEI distributions in the Arctic Ocean. Particularly with respect to the receding sea ice cover, it is imperative to understand how TEIs impact vital functions of the Arctic system, such as primary productivity or, more generally, the cycling of carbon under these rapidly changing environmental conditions. To further understanding on water movement and thus trace element distributions in the Arctic, this team of researchers will measure chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), tritium, helium isotopes, stable isotopes of water and C-14 along the transect. These tracers have been used successfully in past studies for determination of water mass composition, circulation pathways, and mean residence times on time scales from less than one year (CFCs/SF6 and tritium/He-3) to several hundred years (C-14). The researchers plan to make underway measurements of the saturations of CFCs and SF6 in partially and totally ice covered waters along the cruise track, and will also calculate forward and backward sea ice trajectories at all station locations to determine sources of sea ice samples. These trajectories will be used as a first step towards understanding the pathways of waters in the surface mixed layer.