Physical Control of Carbon Export in the Subarctic Pacific

知识价值：物理和生物地球化学海洋学界最大的突出和正在进行的研究问题之一涉及海洋表面初级生产产生的有机碳的命运。尽管碳出口对全球二氧化碳浓度有着深远的控制作用？在美国大气中，生产速率的现场测量结果与从全球年平均推断的结果不完全一致，而且各种海洋环境中碳输出的变率谱尚未完全确定。评估海洋代谢的一种流行方法是氧质量平衡的公式，其中在混合层或光带构建氧预算，去除物理过程的影响，剩余氧产量与向深度输出的碳在化学计量上相关。虽然舰载氧质量平衡研究在很大程度上受到费用和资源可用性的阻碍，但最近使用系泊传感器远程测量氧气的努力显示出相当大的潜力，可以在成本效益和地理范围内广泛诊断生物泵。这些技术已经扩展到移动自主平台，如剖面Argo浮子和海洋滑翔机，它们提供了一个增强的、高分辨率的垂直和水平图像，用于控制初级生产的主要物理过程。随着自主平台净生物产氧量研究的不断发展，该项目将对前所未有的持续时间和分辨率的遥感时间序列进行全面的物理和氧气质量平衡评估：位于阿拉斯加湾南部的华盛顿大学滑翔机海洋站P时间序列。从2008年6月到2010年1月，三个独立的滑翔机部署在仪器良好的美国国家海洋和大气管理局太平洋海洋环境实验室（NOAA/PMEL） P站系泊轨道上，收集基本物理特性、生物光学变量和溶解氧的详细垂直和水平剖面。在这段时间的较长时间内，P站系泊观测了近表层海洋内的大气变量和相应的物理参数；这些数据集合在一起，是一种强大的工具，可以对亚北极太平洋中部的物理变率和净氧产量的既定图景进行补充。在我们提出的分析过程中，我们希望：1)更好地约束水平平流、垂直平流和纵向混合过程，因为它们适用于活性示踪剂的预算；2)在时间序列过程中获得混合层净产氧量的鲁棒估计；3)评估混合层以下和永久盐跃层以上的呼吸（耗氧量）；4)估计背斜下呼吸深度对呼吸的依赖性。更广泛的影响：该项目将扩大控制阿拉斯加湾生物泵的物理动力学的知识库，并增加在碳出口背景下分析的时间序列的长度。更好地了解平流在表层将允许比较以前的残差估计和它在季节周期的每个阶段的相对重要性。探索潜流扩散率在时间和深度上的依赖关系，将改善和澄清我们对其在p站氧气垂直输送中的作用的认识。此外，对系泊和自动驾驶车辆时间序列的组合分析，将为未来在世界海洋难以观测区域的类似部署提供技术基础。

Intellectual Merit: One of the largest outstanding and ongoing research problems in the physical and biogeochemical oceanographic community concerns the fate of organic carbon generated from primary production in the surface ocean. Though carbon export exerts a profound control on CO2 concentrations in the world?s atmosphere, in-situ measurements of production rates are not fully reconciled with those inferred from the global annual average, and the spectrum of variability of carbon export in a variety of oceanic environments has yet to be fully determined. A popular method for evaluating ocean metabolism is the formulation of an oxygen mass balance, in which an oxygen budget is constructed in the mixed layer or euphotic zone, the effects of physical processes are removed, and the residual oxygen production is stoichiometrically related to the export of carbon to depth. While ship-based oxygen mass balance studies are hindered largely by expense and the availability of resources, recent efforts using remote measurement of oxygen from moored sensors display considerable potential for cost-effective and geographically widespread diagnostics of the biological pump. These techniques have been expanded to mobile autonomous platforms such as profiling Argo floats and ocean gliders, which offer an enhanced, highly-resolved vertical and horizontal picture of major physical processes controlling primary production.Continuing the evolution of studies of net biological oxygen production from autonomous platforms, the project will apply a comprehensive physical and oxygen mass balance assessment to a remote-sensing time series of unprecedented duration and resolution: the University of Washington Seaglider Ocean Station P time series in the southern Gulf of Alaska. Three separate Seaglider deployments orbited the well-instrumented National Oceanic and Atmospheric administration Pacific Marine Environmental Laboratory (NOAA/PMEL) Station P mooring from June 2008 to January 2010, collecting detailed vertical and horizontal profiles of basic physical properties, bio-optical variables, and dissolved oxygen. During extended portions of this time, the Station P mooring observed atmospheric variables and corresponding physical parameters within the near surface ocean; taken together these datasets represent a powerful tool for adding to the established picture of physical variability and net oxygen production in the central subarctic Pacific Ocean. In the course of our proposed analysis, we hope to: 1) better constrain horizontal advection, vertical advection, and diapycnal mixing processes, as they apply to the budget of an active tracer; 2) obtain a robust estimate of net oxygen production in the mixed layer during the course of the time series; 3) evaluate respiration (oxygen consumption) below the mixed layer and above the permanent halocline; and 4) estimate the dependence with depth of respiration below the pycnocline. Broader Impacts: This project will expand the knowledge base of the physical dynamics controlling the biological pump in the Gulf of Alaska as well as add to the length of the time series which has been analyzed in a carbon export context. A better understanding of advection in the surface layer would allow comparison to previous residual estimates of this term and its relative importance at each phase of the seasonal cycle. Exploring the dependence in time and depth of diapycnal diffusivity would improve and clarify our knowledge of its role in vertical transport of oxygen at Station P. Additionally, analysis of a combined moored and autonomous vehicle time series should provide a foundation of techniques to be used in similar future deployments in difficult-to-observe regions of the world ocean.