GEOTRACES Pacific Section: Resolving Silicon Isotope Anomalies in the Eastern Pacific

圣巴巴拉的加州大学的一名科学家将获得2013年从秘鲁到塔希提岛的GEOTRACES巡航期间收集的水柱样本。 将对样品进行硅（Si）同位素分析，以获得太平洋海盆Si同位素分布的第一个主要部分。 由于样带涵盖了一个大的梯度初级生产力从上升流区关闭秘鲁的寡营养亚热带环流塔希提岛附近的研究人员将确定如何硅的行为在高生产力沃茨相对于寡营养沃茨。 具体而言，要测试的假设是，硅同位素分布控制的硅同位素分馏过程中的二氧化硅生产和二氧化硅溶解耦合到移动的硅的生物泵和螺旋翻转循环。 此外，科学家计划与来自斯坦福大学、马萨诸塞州大学、达特茅斯和布朗大学的研究人员合作，他们将测量同一截面上硝酸盐的稳定同位素组成，以确定硅和氮同位素是否可以用来预测秘鲁和塔希提岛之间观察到的生产力梯度内的营养消耗模式。 将与加州大学圣克鲁斯研究人员合作评估Fe在Si动力学中的作用，该研究人员将测量巡航期间收集的表面沃茨中的总[Fe]。 最后，利用这些数据，科学家计划测试PANDORA模型的预测能力，并通过在北太平洋引入海底硅源来模拟东北太平洋硅酸烟羽的输入来改进模型。至于更广泛的影响，作为该项目的一部分，将支助和培训一名本科生。

A scientist from the University of California, Santa Barbara will obtain water column samples collected during the 2013 GEOTRACES cruise from Peru to Tahiti. The samples will be analyzed for silicon (Si) isotopes to obtain the first major section of Si isotope distributions in the Pacific Ocean basin. Because the transect covers a large gradient in primary productivity from the upwelling zone off Peru to the oligotrophic subtropical gyre near Tahiti the researcher will determine how Si behaves within high productivity waters relative to oligotrophic waters. Specifically, the hypothesis to be tested is that Si isotope distributions are controlled by fractionation of Si isotopes during silica production and silica dissolution coupled to movement of Si by the biological pump and the meridional overturning circulation. In addition, the scientist plans to collaborate with researchers from Stanford University, the University of Massachusetts, Dartmouth, and Brown University who will measure the stable isotopic composition of nitrate on the same section, to ascertain whether Si and nitrogen isotopes can be used to predict nutrient depletion patterns within the gradient in productivity observed between Peru and Tahiti. The role of Fe in Si dynamics will be evaluated in collaboration with a University of California, Santa Cruz researcher who will measure total [Fe] in surface waters collected during the cruise. Lastly, with the data, the scientist plans to test the prediction capabilities of the PANDORA model, as well as improve the model by incorporating a benthic source of Si in the North Pacific to simulate the inputs of the Northeast Pacific Silicic Acid Plume. As regards broader impacts, one undergraduate student would be supported and trained as part of this project.