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Physical Modulation to the Biological Production in the South China Sea: A Physical-Biological Coupled Model Approach.

机译：对南海生物生产的物理调节：一种物理-生物耦合模型方法。

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摘要

South China Sea (SCS) is a typical marginal sea with the characteristics of open ocean. This distinct property makes SCS an ideal environment to study the modulation mechanisms from various physical processes to the marine biogeochemical (BGC) system. In order to comprehensively investigate the role of various physical processes, such as oceanic circulation, mesoscale eddies, atmospheric forcing, and oceanic fronts, two case studies were conducted in this dissertation with focus on the two hotspots identified by reviewing previous literatures on the BGC systems of the SCS, i.e., winter bloom in the Luzon Strait (referred as LZB), and the summer Vietnam boundary upwelling system (VBUS).;For the case study on the LZB, a coupled physical-biological (TFOR-NPZD) model was developed in order to study the mechanisms. Based on a simulation for 2010, the results showed that the TFOR-NPZD model was capable of reproducing the key features of the LZB, such as the location, inverted-V shape, twin-core structure and bloom intensity. The simulation showed that the LZB was triggered during the relaxation period of intensified northeasterly winds of the winter monsoon, when the deepened mixed layer started to shoal. Nutrient diagnostics showed that vertical mixing was responsible for the nutrient supply to the upper ~40 m layer, while subsurface upwelling supplied nutrients to the region below the mixed layer. Hydrodynamic diagnostics showed that the advection of relative vorticity (RV) primarily contributed to the subsurface upwelling. The RV advection was resulted from an offshore jet, which was associated with a northeasterly wind, flowed across the ambient RV field.;For the process-oriented case study on the VBUS, investigation on the remote sensing data revealed a tight spatio-temporal covariance of the biological productivity and the circulation. High level of biological production was associated with high level of surface current intensity, which accounted for ~12% of the variability in the production. A coupled physical-biological (TFOR-CoSiNE) model with the emphasis on the mesoscale phenomena was developed to study the detailed processes in VBUS. Validation against satellite and in-situ data suggested that the capability of the model system in reproducing the key features of the summer VBUS, including the positive contribution from the circulation. Inspection into the model results highlighted the circulation's role in local BGC system, where the separation and the anticyclone pattern from the circulation were favorable for the recycling of the nutrients. The weakened circulation was associated with an abnormal non-separated circulation pattern, which would leak the organic matters and reduce the nutrient inventory in the VBUS. In a numerical experiment where the circulation was manipulated presenting a weak tendency of separation, the nitrate inventory could be reduced by ~25% while the production reduced by ~16%, demonstrating the significance of the circulation's role.;The previous two case studies demonstrate that the above-mentioned physical processes not only redistribute the water with high biological productivity, but also systematically modify the source-and-sink pattern of nutrient (mainly nitrogen) as the most important limiting factor of biological production in the oligotrophic SCS. By inducing vertical motion of water mass and horizontal transport of high nutrient coastal water, physical processes fuel the nutrient available for biological production in the upper layer via various mechanisms. Thus, the BGC cycle in the SCS is highly modulated by the physical dynamical processes.
机译：南海（SCS）是典型的边缘海，具有开放海洋的特征。这种独特的特性使SCS成为研究从各种物理过程到海洋生物地球化学（BGC）系统的调节机制的理想环境。为了全面研究海洋循环，中尺度涡旋，大气强迫和海锋等各种物理过程的作用，本论文进行了两个案例研究，重点是通过回顾以往有关BGC系统的文献确定的两个热点SCS的特征，即吕宋海峡的冬季开花（简称LZB）和越南的夏季边界上升流系统（VBUS）。对于LZB的案例研究，采用了一种物理-生物耦合（TFOR-NPZD）模型为了研究机理而开发。基于2010年的模拟，结果表明TFOR-NPZD模型能够重现LZB的关键特征，例如位置，倒V形，双核结构和大华强度。模拟表明，LZB是在冬季季风加剧的东北风的松弛期触发的，此时加深的混合层开始浅滩化。营养诊断表明，垂直混合是向上40 m上部营养物供应的原因，而地下上升流则向混合层以下区域营养物供应。流体动力学诊断表明，相对涡度（RV）的平流主要是造成地下上升的原因。 RV平流是由一股与东北风相关的近海射流引起的；该喷气流流过周围RV场。对于VBUS的过程导向案例研究，对遥感数据的调查显示出紧密的时空协方差生物生产力和循环。高水平的生物生产与高水平的表面电流强度相关，约占生产变异性的12％。开发了一个以中尺度现象为重点的物理-生物（TFOR-CoSiNE）耦合模型，以研究VBUS中的详细过程。对卫星和现场数据的验证表明，该模型系统具有再现夏季VBUS关键特征的能力，包括循环的积极贡献。对模型结果的检查突出了循环在本地BGC系统中的作用，其中从循环中分离和反旋风模式有利于营养物的循环利用。弱化的循环与异常的非分离循环模式有关，这会泄漏有机物并减少VBUS中的养分库存。在一个数值模拟实验中，通过操纵循环表现出较弱的分离趋势，硝酸盐库存可减少约25％，而产量减少约16％，证明了循环作用的重要性。前两个案例研究表明上述物理过程不仅以高生物生产力重新分配水，而且系统地改变了营养（主要是氮）的源-库模式，这是贫营养型南海生物生产的最重要限制因素。通过诱导水团的垂直运动和高养分沿海水的水平输送，物理过程通过各种机制为上层生物生产提供了养分。因此，SCS中的BGC循环受到物理动力学过程的高度调制。

著录项

  • 作者

    Lu, Wenfang.;

  • 作者单位

    University of Delaware.;

  • 授予单位 University of Delaware.;
  • 学科 Physical oceanography.;Biological oceanography.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 134 p.
  • 总页数 134
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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