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)确定选定的微量元素和同位素的全球海洋分布，并评估这些物种的源、汇和内部循环，以更全面地描述调节它们分布的物理、化学和生物过程；(2)了解控制过去环境中用于替代环境的地球化学物种浓度的过程。由于海洋中痕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天气测量，否则实现GEOTRACES的目标将是非常困难的，如果不是不可能的话。在这个项目中，华盛顿大学的研究人员将参加2013年美国GEOTRACES太平洋行动，以确定区域海洋碳系统的特征。他们将使用两种方法。首先，他们将测量溶解无机碳的13C/12C稳定碳同位素比(Del13C)的深度分布，这已被国际地球科学计划指定为关键参数，并具有最高的测量优先级。其次，他们将根据溶解的O2/Ar气体比率来估计表层有机物(OM)的输出速率。Del13C的测量将在大约22个站进行，总共有525个样品。此外，他们将使用在其他海洋区域广泛使用的在航测量方法，以~5公里的空间分辨率测量表层的溶解O2/Ar气体比率。邮轮航道将横跨从秘鲁沿海上升流带到塔希提岛周围的少营养环流的广泛的生物生产力体系。拟议的基于O2/Ar的高分辨率OM出口率应清楚地检测到预期的境外OM出口下降，并确定生产率的过渡区或前沿。预计较大的近海生产力梯度将提供机会，以确定表层有机质输出和深部有机质降解对上层海洋深度Del13C、微量元素(TES)、O2和营养物质分布的影响。GEOTRACES期间对Del13C和TE的初步测量表明，有可能增进我们对现代海洋中控制Del13C、TES和营养物质分布的过程的理解，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，并纳入国际海洋学研究所的研究生和本科生教学课程。此外，将有本科生(目前有5名学生)积极参与为del13C分析准备样品。

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.