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

加州大学圣巴巴拉分校的一名科学家将获取2013年从秘鲁到塔希提岛的GEOTRACES邮轮上采集的水柱样本。这些样品将被分析硅(Si)同位素，以获得太平洋盆地硅同位素分布的第一个主要部分。由于样带覆盖了初级生产力的很大梯度，从秘鲁附近的上升带到塔希提岛附近的低营养亚热带环流，研究人员将确定硅在高生产力水域中相对于低营养水域的表现。具体地说，要检验的假设是，硅同位素分布受二氧化硅生产过程中硅同位素的分馏和硅的溶解以及生物泵对硅的移动和子午线翻转环流的控制。此外，这位科学家计划与斯坦福大学、马萨诸塞大学、达特茅斯大学和布朗大学的研究人员合作，他们将在同一切片上测量硝酸盐的稳定同位素组成，以确定是否可以使用硅和氮同位素来预测秘鲁和塔希提岛之间观察到的生产力梯度内的养分消耗模式。将与加州大学圣克鲁斯分校的一名研究人员合作，评估铁在硅动力学中的作用，该研究人员将测量邮轮期间收集的地表水中的总[Fe]。最后，这位科学家计划利用这些数据来测试潘多拉模型的预测能力，并通过纳入北太平洋的一个海底硅源来模拟东北太平洋硅酸羽流的输入来改进该模型。至于更广泛的影响，作为该项目的一部分，一名本科生将得到支持和培训。

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.