US GEOTRACES Pacific: Measuring the d13C-DIC distribution and quantifying the impact of organic matter export on d13C, nutrients and trace metals

国际GEOTRACES计划有两个主要目标：(1)确定选定微量元素和同位素的全球海洋分布，评估这些物种的来源、汇和内部循环，以更完整地描述调节其分布的物理、化学和生物过程；(2)了解控制地球化学物种浓度的过程，这些物种被用作过去环境的代用物。由于海洋中微量元素和同位素的循环与碳的有机和无机生物地球化学转化密切相关，除非对有机和无机海洋碳系统进行综合测量，否则实现GEOTRACES的目标将是非常困难的，甚至是不可能的。在这个项目中，华盛顿大学的研究人员将参加2013年美国geotraces太平洋活动，以表征区域海洋碳系统。他们将采用两种方法。首先，他们将测量溶解无机碳13C/12C稳定碳同位素比（del13C）的深度分布，这是国际GEOTRACES科学计划指定的关键参数，具有最高的测量优先级。其次，他们将根据溶解的O2/Ar气体的比率估计从表层输出的有机物（OM）的速率。del13C的测量将在大约22个站点进行，总共约525个样品。此外，他们将使用一种在其他海洋地区广泛使用的正在进行的测量方法，以~5公里的空间分辨率测量表层溶解的O2/Ar气体比。这条巡游路线将跨越从秘鲁沿海上升流区到塔希提岛周围的少营养环流的广泛生物生产力体系。提出的基于O2/ ar的高分辨率OM出口率应该清楚地检测到预计的离岸OM出口减少，并确定生产力的过渡区或前沿。预期的巨大海上生产力梯度将为确定表层OM输出和深度OM降解对del13C、微量元素（TEs）、O2和营养物质沿剖面的上层海洋深度分布的影响提供机会。GEOTRACES期间的初始del13C和TE测量表明，有可能提高我们对现代海洋中控制del13C、TEs和养分分布的过程的理解，从而提高del13C和TEs作为海洋环流和碳循环过去变化的示踪剂的效用，这是本研究的长期目标。更广泛的影响。这些数据和研究成果将广泛分发给国际海洋学和古气候学界，并纳入PI的研究生和本科教学课程。此外，将有本科生积极参与（目前有5名学生）准备样品进行del13C分析。

The international GEOTRACES program has two major goals: (1) to determine global ocean distributions of selected trace elements and isotopes and evaluate the sources, sinks, and internal cycling of these species to characterize more completely the physical, chemical and biological processes regulating their distributions; and (2) to understand the processes that control the concentrations of geochemical species used for proxies of the past environment. Because the cycling of trace elements and isotopes in the sea is intimately connected with both the organic and the inorganic biogeochemical transformations of carbon, the achievement of the goals of GEOTRACES would be very difficult if not impossible unless synoptic measurements are also made on the organic and inorganic marine carbon system.In this project, researchers at the University of Washington will participate in the U.S.GEOTRACES Pacific campaign in 2013 to characterize the regional ocean carbon system. They will use two approaches. First, they will measure the depth distribution of the 13C/12C stable carbon isotopic ratio of the dissolved inorganic carbon (del13C), which has been designated in the international GEOTRACES Science Plan as a key parameter and has the highest measurement priority. Second, they will estimate the rate of organic matter (OM) export from the surface layer based on dissolved O2/Ar gas ratios. Measurements of del13C will be made at about 22 stations for a total of ~525 samples. Additionally, they will measure the dissolved O2/Ar gas ratio at ~5 km spatial resolution in the surface layer using an underway measurement method that has been used extensively in other oceanic regions. The cruise track will cross a wide range of biological productivity regimes from the coastal upwelling zone off Peru to the oligotrophic gyre surrounding Tahiti. The proposed high resolution O2/Ar-based OM export rates should clearly detect the expected offshore decrease in OM export and locate transition zones or fronts in productivity. The expected large offshore productivity gradient will provide the opportunity to determine the impact of OM export from the surface layer and OM degradation at depth on upper ocean depth distribution of del13C, trace elements (TEs), O2 and nutrients along the section. The initial del13C and TE measurements during GEOTRACES illustrate the potential to improve our understanding of the processes that control del13C, TEs and nutrient distributions in the modern ocean and, as a result, improve the utility of del13C and TEs as tracers of past changes in the ocean circulation and carbon cycling, which is a long term goal of this research. Broader Impacts. The data and research results will be broadly distributed to the international oceanographic and paleoclimate communities and incorporated into the PI's graduate and undergraduate teaching curricula. Additionally, there will be active undergraduate participation (5 students currently) in preparing samples for del13C analyses.