Physical Control of Carbon Export in the Subarctic Pacific

智力价值：物理和生物地球化学海洋学领域最大的悬而未决和正在进行的研究问题之一涉及表层海洋初级生产产生的有机碳的命运。尽管碳出口对全球大气中的二氧化碳浓度有着深刻的控制作用，但现场测量的碳排放速率与从全球年平均水平推断的碳排放速率并不完全一致，而且碳出口在各种海洋环境中的变化谱还没有完全确定。评估海洋新陈代谢的一种流行方法是建立氧质量平衡公式，其中在混合层或真光层建立氧平衡，消除物理过程的影响，剩余氧产生与向深度输出碳的化学计量相关。虽然船载氧物质平衡研究在很大程度上受到费用和资源可获得性的阻碍，但最近使用系泊传感器远程测量氧的努力显示出相当大的潜力，可以用于经济高效和地理上广泛的生物泵诊断。这些技术已经扩展到移动自主平台，如剖析Argo浮标和海洋滑翔机，这些平台提供了控制初级生产的主要物理过程的增强的、高分辨率的垂直和水平图像。随着自主平台净生物氧生产研究的进展，该项目将对一个持续时间和分辨率前所未有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海洋滑翔机海洋站P时间序列。从2008年6月到2010年1月，三个独立的Seaglider部署在仪器齐全的国家海洋和大气管理局太平洋海洋环境实验室(NOAA/PMEL)P站系泊中，收集基本物理性质、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里，P站系泊观测到近地表海洋内的大气变量和相应的物理参数；这些数据集加在一起，是增加中央次北极太平洋物理变率和净产氧量的既定图景的有力工具。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、垂直平流和昼夜混合过程，因为它们适用于活动示踪剂的预算；2)获得时间序列过程中混合层中净氧气生产的可靠估计；3)估计混合层以下和永久盐跃层以上的呼吸(氧耗)；以及4)估计与跃层以下呼吸深度的相关性。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，并增加已在碳出口背景下分析的时间序列的长度。如果能更好地了解表层平流，就可以与以前对这一术语的剩馀估计数及其在季节周期每一阶段的相对重要性进行比较。探索日平均扩散系数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了解。此外，对系泊和自动驾驶车辆时间序列的分析应为今后在世界海洋难以观测的区域进行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.