Collaborative Research: Use of Triple Oxygen Isotopes and O2/Ar to constrain Net/Gross Oxygen Production during upwelling and non-upwelling periods in a Coastal Setting

海洋生物泵是将人为二氧化碳从大气中隔离并以有机碳的形式输出到深海的主要途径之一。虽然上升流区域的营养供应与高初级生产力之间的联系已经确立，但控制上升流生态系统有机碳输出效率的因素尚不清楚。南加州大学和波莫纳学院的科学家们计划在圣佩德罗海洋时间序列中确定控制生物生产的两个组成部分的速率和大小的因素，净群落生产（NCP）和总初级生产（GPP），以及颗粒有机碳输出效率。圣佩德罗海洋时间序列是加利福尼亚边境地区的一个沿海地点，在2年的时间内，在最小和高上升流速度期间。在这个地点，过去和正在进行的水文和碳雨观测将为解释结果和工作机制提供历史背景。利用溶解氧/氩（O2/Ar）比值和溶解氧（O2）的氧三重同位素组成，定量分析不同上升流强度下的NCP和GPP速率。有机碳的出口将利用水柱中的234（钍）剖面，加上浮动沉积物捕集器的部署，以及水柱碳同位素平衡的发展。上升流的特征将使用大气7Be（铍）输入的非稳态预算及其深度集成衰变，以及基于风应力旋度的远程测量和溶解无机碳和硅的预算来估计速率。O2/Ar比值和氧三重同位素方法的应用将需要这些示踪剂的深度综合剖面，以评估上升流对混合层输入的影响，并在上升流的季节转换期间使用非稳态模型。将获得的综合数据集应提供对可变上升流制度下有机碳输出效率的见解，并有助于将叶绿素的卫星测量与这些高产生态系统的有机碳输出联系起来。更广泛的影响：作为该项目的一部分，南加州大学的一名研究生和一名本科生以及波莫纳学院的两名本科生将得到支持和培训。

The marine biological pump is one of the primary pathways via which anthropogenic carbon dioxide may be sequestered from the atmosphere and exported to the deep ocean as organic carbon. While the link between nutrient supply and high primary productivity in upwelling regions is well established, factors controlling the organic carbon export efficiency of upwelling ecosystems are not well known. Scientists from the University of Southern California and Pomona College plan to determine the factors that control the rates and magnitudes of two components of biological production, Net Community Production (NCP) and Gross Primary Production (GPP), as well as particulate organic carbon export efficiency, at the San Pedro Ocean Time Series, a coastal site in the California Borderland during periods of minimal and high upwelling velocity over a 2-year span. At this site, past and ongoing observations of hydrography and carbon rain will provide an historical context for interpreting results and mechanisms at work. Rates of NCP and GPP will be quantified at different upwelling intensity, using dissolved oxygen to argon (O2/Ar) ratios and the oxygen triple isotope composition of dissolved oxygen (O2). The export of organic carbon will be established using 234Th (thorium) profiles in the water column, coupled with floating sediment trap deployments, and the development of a carbon isotope balance for the water column. Upwelling will be characterized using non-steady state budgets for atmospheric 7Be (beryllium) input and its depth-integrated decay, as well as estimating rates based on remote measurements of wind stress curl and budgets for dissolved inorganic carbon and silicon. Application of the O2/Ar ratio and the oxygen triple isotope approach will require depth-integrated profiles of these tracers to evaluate the impact of upwelling on mixed layer inputs and use of non-steady state models during seasonal transitions in upwelling. The comprehensive data set to be obtained should provide insights into the organic carbon export efficiency under variable upwelling regimes and help to relate the satellite-based measurements of chlorophyll to the organic carbon export of these highly productive ecosystems.Broader Impacts: One graduate and one undergraduate student from the University of Southern California and two undergraduate students from Pomona College would be supported and trained as part of this project.