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）确定全球海洋中某些微量元素和同位素的分布，评估这些物种的源、汇和内部循环，以更全面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，这些地球化学物种被用作过去环境的替代物。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，如果不对有机和无机海洋碳系统进行天气测量，实现GEOTRACES的目标即使不是不可能，也是非常困难的。2013年，华盛顿大学的研究人员将参加美国的GEOTRACES太平洋活动，以描述该地区海洋碳系统的特征。 他们将使用两种方法。 首先，他们将测量溶解无机碳的13 C/12 C稳定碳同位素比值（del 13 C）的深度分布，该比值在国际GEOTRACES科学计划中被指定为关键参数，具有最高的测量优先级。其次，他们将根据溶解的O2/Ar气体比率估计有机物（OM）从表层输出的速率。 将在大约22个站点对总共约525个样本进行del 13 C测量。此外，他们将使用在其他海洋区域广泛使用的正在进行的测量方法，以约5公里的空间分辨率测量表层溶解的O2/Ar气体比率。考察路线将穿越从秘鲁沿海上升流区到塔希提岛周围贫营养环流的各种生物生产力状况。建议的高分辨率O2/Ar基OM输出率应清楚地检测OM输出的预期海上下降，并定位生产力的过渡区或前沿。预期的大的近海生产力梯度将提供机会，以确定从表层输出的有机质和有机质在深度上的del 13 C，微量元素（TEs），O2和营养物沿着部分的上层海洋深度分布的降解的影响。 GEOTRACES期间的初始del 13 C和TE测量说明了提高我们对控制del 13 C，TE和现代海洋中营养物分布的过程的理解的潜力，因此，提高了del 13 C和TE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的研究生和本科生教学课程。 此外，将有积极的本科生参与（目前5名学生）在准备样品del 13 C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.