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

来自加州大学圣巴巴拉分校的一名科学家将获得2013年GEOTRACES从秘鲁到塔希提岛巡游期间收集的水柱样本。将对样品进行硅（Si）同位素分析，以获得太平洋盆地硅同位素分布的第一个主要剖面。由于样带覆盖了从秘鲁附近的上升流区到塔希提岛附近的少营养亚热带环流的初级生产力的很大梯度，研究人员将确定相对于少营养水域，Si在高生产力水域中的表现。具体来说，需要验证的假设是，硅同位素分布受硅同位素在硅生产过程中的分馏和硅溶解以及生物泵和经向翻转环流耦合的硅运动的控制。此外，这位科学家计划与来自斯坦福大学、麻省大学、达特茅斯大学和布朗大学的研究人员合作，他们将在同一剖面上测量硝酸盐的稳定同位素组成，以确定Si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养分消耗模式。铁在硅动力学中的作用将与加州大学圣克鲁兹分校的一名研究人员合作进行评估，该研究人员将测量在巡航期间收集的地表水中的总[铁]。最后，利用这些数据，科学家计划测试PANDORA模型的预测能力，并通过加入北太平洋的底栖硅源来模拟东北太平洋硅酸羽流的输入来改进模型。至于更广泛的影响，一名本科生将得到支持和培训，作为该项目的一部分。

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.