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GEOTRACES北极考察的研究人员将测量六种海洋示踪剂，以更好地了解北冰洋的海洋水运动。 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GEOTRACES计划中的其他国家倡议一样，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，并确定这些分布对环境条件变化的敏感性。一些微量元素是生命所必需的，另一些是已知的生物毒素，还有一些是重要的，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。作为本研究的一部分，被测量的示踪剂已经证明了它们在短到长的时间尺度上对水体组成、循环和平均停留时间的研究的价值。该项目还将为两名高中教师提供培训，并为高中学生编制课程。北极目前正以地球仪上其他地方所未见的速度经历着系统规模的环境变化。因此，有必要建立一个基线的微量元素和同位素（TEI）的分布为未来的参考，并开始了解的过程，确定在北冰洋的TEI分布。特别是在海冰覆盖面积减少的情况下，必须了解TEIs如何影响北极系统的重要功能，例如初级生产力，或者更一般地说，在这些快速变化的环境条件下的碳循环。为了进一步了解北极地区的水运动和微量元素分布，这支研究团队将测量氯氟烃（CFCs）、六氟化硫（SF6）、氚、氦同位素、水的稳定同位素和C-14沿着。这些示踪剂已被成功地用于在过去的研究确定水的质量组成，循环途径，并在时间尺度上从不到一年（CFCs/SF6和氚/He-3）到几百年（C-14）的平均停留时间。研究人员计划在巡航轨道沿着部分和完全被冰覆盖的沃茨中对CFC和SF6的饱和度进行测量，并将计算所有站点位置的向前和向后海冰轨迹，以确定海冰样本的来源。这些轨迹将被用来作为第一步了解的路径沃茨在表面混合层。

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.