US GEOTRACES ARCTIC: Measuring stable isotopes of carbon in dissolved inorganic carbon and oxygen/argon gas ratios to show impact of organic matter export on nutrient distributions

来自华盛顿大学的一名科学家将参加2015年美国GEOTRACES北冰洋巡航，并测量溶解无机碳（del13C）中碳的稳定同位素的垂直分布，del13C是生物地球化学循环的示踪剂。此外，他将确定地表水样品中氧气与氩气（O2/Ar）的比例的空间变化，因为这个比例可以作为有机物输出的代表。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。这项研究的结果将进一步加深我们对当今海洋中观察到的微量元素、营养物质和溶解无机碳中稳定碳同位素的控制过程的理解，并利用这些信息获得过去海洋环流对碳循环的变化的信息。该项目还将为本科生提供培训机会，并将成果纳入公共宣传活动和课堂讲座材料。更好地了解物理和生物过程对现代海洋中营养和微量元素分布的影响，对于我们解释它们在北极分布的未来变化以及它们作为历史海洋环流和生物泵条件的代用物的效用至关重要。了解这些过程所需的一个关键参数是溶解无机碳的del13C，目前在北冰洋中几乎没有相关数据。本研究旨在测量海洋表层溶解无机碳del13C和溶解O2/Ar比值的深度分布。这些测量将有助于量化化学过程和生物泵对营养物质、微量元素和del13C空间分布的贡献，并估计海洋表面有机物的输出速率。

A scientist from the University of Washington will participate in the 2015 U.S. GEOTRACES Arctic Ocean cruise and measure the vertical distribution of the stable isotopes of carbon found in dissolved inorganic carbon (del13C), a tracer of biogeochemical cycling. In addition, he will determine the spatial variation in the ratio of oxygen gas to argon gas (O2/Ar) in surface water samples because this ratio can be used as a proxy for organic matter export. 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. Results from this study will further our understanding of the processes that control observed trace elements, nutrients, and the stable carbon isotopes in dissolved inorganic carbon in the present day ocean and use this information to gain information on past changes in ocean circulation on carbon cycling. This project will also provide training opportunities for undergraduate students, and results will be integrated into public outreach activities and material for class lectures.A better understanding of the impact of physical and biological processes on the distribution of nutrient and trace elements in the modern ocean is critical to our interpretation of future changes in their distributions in the Arctic and their utility as proxies of circulation and biological pump conditions in the historic ocean. One key parameter needed to understand these processes is del13C of dissolved inorganic carbon, for which little to no data currently exists in the Arctic Ocean. This study will aim to measure the depth distribution of the del13C of dissolved inorganic carbon and the dissolved O2/Ar ratio in the surface layer of the ocean. These measurements will help to quantify the contributions of chemical processes and the biological pump on the spatial distribution of nutrients, trace elements, and del13C, as well as estimate organic matter export rates from the surface ocean.