The Role of New Technology in Advancing Ocean Biogeochemical Research
The Role of New Technology in Advancing Ocean Biogeochemical Research
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DOI：
10.5670/oceanog.2001.11
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发表时间：
2001
期刊：
影响因子：
2.8
通讯作者：
T. Dickey
中科院分区：
文献类型：
--
作者：
T. Dickey
大气中二氧化碳（CO2）水平的迅速增加激发了人们对了解海洋生物地球化学过程及其与大气相互作用的兴趣。有趣的是，据报道，在夏威夷和百慕大附近的联合全球海洋通量研究（JGOFS）海洋时间序列站点，表面二氧化碳也在上升。CO~水平上升的潜在影响包括全球大气和海洋温度升高、冰盖融化、海平面上升以及区域天气模式的变化，这些都会导致干旱和洪水。一个重要的问题是，我们是否有能力区分自然和人为因素对海平面上升的影响。另一个问题是海洋在二氧化碳循环和变化中所扮演的角色。这些问题和其他悬而未决的问题刺激了JGOFS的发展和实施。JGOFS是一个多学科的国际项目，于1987年至2001年由20多个国家开展。JGOFS旨在研究海洋生物地球化学循环及其与气候变化的相互作用。在千年的时间尺度上，海洋决定了大气中二氧化碳的浓度。海洋中溶解无机碳（DIC）的梯度是相反的，因此DIC的浓度越深越高。相反，水柱的上部与大气处于一阶的总体平衡状态。这种梯度由两个碳“泵”维持。“溶解度泵”取决于冷水比温水含有更多二氧化碳的事实；例如，寒冷的深水的溶解度大约是近赤道表层水的两倍。因此，表层海水通过温盐环流下沉的净效应是使深层水域的碳含量增加。第二种碳泵被称为“生物泵”，是本综述新技术和观察的主要焦点（见Ducklow等人，本期）。生物泵的过程始于生活在海洋上层或真光层的浮游植物。浮游植物吸收二氧化碳和营养物质形成有机物。虽然这些有机物质中的大部分在地表水中被代谢和再循环，但有很大一部分（大约10%到20%，但随时间和空间的变化很大）在通过微生物的代谢被再矿化成无机形式之前沉入深海。洋流和上升流将二氧化碳送回海洋表面，但生物泵的总体效果是将碳输送到深海。溶解度和生物泵对大气CO2水平有显著影响。生物泵包括通过溶解有机碳（DOC）分子（见Hansell和Carlson，本期）和颗粒有机碳（POC）物质（见Berelson，本期）向深层输出碳的途径。确定上层海洋的初级产量是量化POC形成的关键步骤，POC随后可通过生物泵输送。以下几段介绍了与生物泵相关的初级生产的一些关键概念，重点是通过系泊和其他平台的自主测量来量化生物泵。生物泵是研究生物光学和上层海洋物理以及生物地球化学的研究人员感兴趣的。初级生产力和浮游植物生物量取决于光合作用过程，这隐含地涉及光的可利用性（以光合有效辐射或[PAR]衡量）和硝酸盐、硅酸盐、磷酸盐和铁等营养物质。光的光谱质量和强度随深度的变化而变化，这对具有特殊色素沉着或光适应特征的特定浮游植物物种很重要。个体生物的光暴露受到物理条件变化的影响，包括混合层深度、湍流和电流，以及入射的太阳辐射，所有这些都在时间和空间上变化。一个重要的反馈关系到光谱光场的调制
Introduction The rapid increase in atmospheric carbon dioxide (CO2) levels has stimulated a growing interest in understanding biogeochemical processes in the ocean and their interactions with the atmosphere. Interestingly, surface CO2 is also reported to be rising at the Joint Global Ocean Flux Study (JGOFS) ocean time series sites off Hawaii and Bermuda. Potential effects of rising CO~ levels include increases in global atmospheric and oceanic temperatures, melting of ice caps, sea-level rise and shifts in regional weather patterns, that lead to droughts and floods. One important question concerns our ability to discern natural versus anthropogenic contributions to this rise. Another question concerns the role the ocean plays in the cycling and variability of CO2. These and other unanswered questions stimulated the development and execution of JGOFS, a multidisciplinary and international program carried out between 1987 and 2001 by more than 20 nations. JGOFS was designed to study oceanic biogeochemical cycles and their interaction with a changing climate. On millennial time scales, the ocean dictates the atmospheric concentration of CO2. There is an inverse gradient in Dissolved Inorganic Carbon (DIC) in the ocean, such that higher concentrations of DIC are found at greater depths. In contrast, the upper portion of the water column is in overall equilibrium with the atmosphere to first order. This gradient is maintained by two carbon "pumps." The "solubility pump" depends on the fact that cold water holds more CO2 than warm water; for example, the solubility of cold, deep water is about twice as great as that of near-surface equatorial water. As a consequence, the net effect of sinking surface waters through thermohaline circulation is to enrich deeper waters in carbon. The second carbon pump is known as the "biological pump", and is the primary focus of this review of new technologies and observations (see Ducklow et al., this issue). The biological pump's process begins with phytoplankton living in the upper or euphotic layer of the ocean. Phytoplankton take up CO2 and nutrients to form organic matter. Although much of this organic matter is metabolized and recycled in the surface waters, a significant portion (roughly 10% to 20% but varying greatly over space and time) sinks into the deep ocean before it is remineralized into an inorganic form via the metabolism of microorganisms. Currents and upwelling return CO2 to the surface of the ocean, but the overall effect of the biological pump is to transport carbon into the deep ocean. The solubility and biological pumps have significant effects on atmospheric CO2 levels. The biological pump includes pathways of carbon export to the deeper layers through Dissolved Organic Carbon (DOC) molecules (see Hansell and Carlson, this issue) and Particulate Organic Carbon (POC) matter (see Berelson, this issue). The determination of primary production in the upper ocean is a vital step in quantifying the formation of POC, which is then available for transport via the biological pump. The following paragraphs introduce some of the key concepts regarding primary production in relation to the biological pump, with a focus on its quantification using autonomous measurements from moorings and other platforms. The biological pump is of interest to researchers studying bio-optics and upper-ocean physics as well as biogeochemistry. Primary productivity and phytoplankton biomass depend on photosynthetic processes, which implicitly involve the availability of light (measured as Photosynthetically Available Radiation or [PAR]) and nutrients such as nitrate, silicate, phosphate, and iron. The spectral quality and intensity of light varies with depth and is important for specific phytoplankton species with special pigmentation or photoadaptive characteristics. Light exposure for individual organisms is affected by variation in physical conditions including mixed layer depth, turbulence and currents, as well as the incident solar radiation, all of which vary in time and space. An important feedback concerns the modulation of the spectral light field