Causes and effects of composition changes in the ocean

海洋成分变化的原因和影响

• 批准号: RGPIN-2016-03783
• 负责人: Pawlowicz, Rich
• 金额: $ 2.4万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=614628
• 关键词: Causes; effects; composition; changes; ocean

Physical oceanographers consider "salinity", a measure of salt content (notionally composed of all seawater constituents with concentrations greater than about 0.001 g/kg), to be conservative - that is, modified only by advective transport, by mixing, and by the addition/removal of pure water at boundaries through evaporation, precipitation, and river inflows. However, these major constituents are not completely conservative, and they undergo a variety of processes in the ocean that result in small changes to the relative chemical composition of sea salt. Chemical oceanographers are well aware of the non-conservative nature of many of these major constituents, but although knowledge about virtually every element in seawater has increased dramatically over the past 50 years, studies of the spatial and temporal variations in the relative amounts of many non-conservative major constituents have been almost completely neglected since the 1960s. Thus, a knowledge gap exists. Scientifically, studying such neglected composition variations, and the physical/chemical mechanisms that give rise to them, may therefore prove to be an exciting area of fundamental interest to global ocean circulation studies. This is because such mechanisms would have traceable consequences that may help oceanographers identify critical transport pathways in the ocean (analogous to the way in which carbon/nutrient changes from remineralization of organic matter track the global thermohaline conveyor). In addition, knowledge of these variations will also improve direct calculations of transport because more accurate knowledge of the density field will be possible. The development of the new TEOS-10 seawater standard has highlighted the fact that the errors in actual salinity estimates, and therefore also in derived parameters like density, which are incurred by ignoring these non-conservative variations, are one to two orders of magnitude larger than the precision with which we currently "measure" salinity. This is one of the two major problems with our current oceanographic definition of salinity when applied to climate science issues (the other is related to metrological aspects of the definition). The objectives of this proposed work are therefore to gain a better quantitative understanding of changes in the major constituent composition of the ocean, primarily by measuring the so-called "salinity anomaly" in different regions through combined conductance/density sampling, and to investigate in detail some of the mechanisms that may give rise to these anomalies, concentrating on double- and multi-diffusive processes that may be important in regions like the Arctic.

物理海洋学家认为“盐度”是保守的，盐度是盐分含量(理论上由浓度大于约0.001克/公斤的所有海水成分组成)的量度，也就是说，只有通过平流输送、混合以及通过蒸发、降水和河流流入在边界上添加/去除纯净水，才能修正盐度。然而，这些主要成分并不是完全保守的，它们在海洋中经历了各种过程，导致海盐的相对化学成分发生了微小的变化。化学海洋学家清楚地意识到这些主要组分的许多非保守性，但尽管关于海水中几乎每一种元素的知识在过去50年中急剧增加，但自20世纪60年代以来，对许多非保守性主要组分相对数量的时空变化的研究几乎完全被忽视。因此，存在着知识鸿沟。 因此，从科学上讲，研究这种被忽视的成分变化及其产生的物理/化学机制可能被证明是全球海洋环流研究的一个令人兴奋的基本兴趣领域。这是因为这种机制将产生可追踪的后果，可能有助于海洋学家确定海洋中的关键运输路径(类似于有机物质再矿化导致的碳/营养变化跟踪全球温盐传送带的方式)。 此外，了解这些变化还将改进对传输的直接计算，因为可以更准确地了解密度场。新的TEOS-10海水标准的制定突显了这样一个事实，即由于忽略这些非保守的变化而引起的实际盐度估计的误差，以及由此产生的密度等参数的误差，比我们目前“测量”盐度的精度大一到两个数量级。这是我们目前对盐度的海洋学定义在应用于气候科学问题时的两个主要问题之一(另一个问题与该定义的计量方面有关)。 因此，这项拟议工作的目的是更好地定量了解海洋主要成分的变化，主要是通过电导/密度联合采样测量不同区域的所谓“盐度异常”，并详细调查可能引起这些异常的一些机制，重点是在北极等区域可能十分重要的双扩散和多扩散过程。