基于细尺度参数化的西北太平洋和南大洋的湍流混合研究

发布时间：2018-01-11 00:09

本文关键词：基于细尺度参数化的西北太平洋和南大洋的湍流混合研究　出处：《中国科学院研究生院(海洋研究所)》2015年博士论文　论文类型：学位论文

【摘要】：内波是普遍存在于稳定层化的海洋内部的一种波动,影响着海洋中的质量、动量和能量的输送。内波间的非线性相互作用将海洋中的能量从大尺度不断地向小尺度传递,从而引起内波破碎,导致跨等密度面的湍流混合(简称湍流混合)。小尺度的湍流混合对于热量输运、水体交换和溶解物质(营养物质与污染物)的垂向输运以及全球气候、热盐环流、海洋环境与生态系统的变化都有重要影响。因此,研究湍流混合的时空变化特征及其影响因素具有重要意义。海洋内部的湍流混合主要是由内波破碎导致,而大量研究表明风生近惯性能量、潮汐以及海流与海底地形的相互作用(尤其在南大洋)是内波场的主要能量来源。本文利用8年JODC (Japan Oceanographic Data Center)和KESS计划(Kuroshio Extension System Study)的温盐深仪(conductivity-temperature-depth, CTD)水文观测剖面资料,基于细尺度参数化方法研究了在西北太平洋地区的跨越等密度面的混合的时空变异,发现：海洋上层300-1800 m湍流混合呈现显著的季节性变化特征,并且在统计上与风生近惯性能量有明显的相关关系：相对于平滑地形,湍流混合系数在地形粗糙的区域加强。因风生近惯性能量和粗糙海底地形而强化的湍流混合可分别穿透到海洋内部1800 m和距海底3300 m处,该穿透距离随着风生近惯性能量和地形粗糙程度的变化而变化。该研究证明了风生近惯性能量的驱动和海底地形的影响对于维持海洋内部的湍流混合有着重要的作用。深海的混合过程使深海的冷水上升到海洋上层,从而形成大洋的经向翻转环流(Meridional Overturning Circulation, MOC)的闭合。在南大洋,28 kgm-3中性密度面可以近似作为上下两层经向翻转环流的分界面。在南极绕极流(Antarctic Circumpolar Current, ACC)区域,本文联合使用Argo (Array for Real-time Geostrophic Oceanography)剖面数据和DIMES (Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean)中的CTD剖面数据,应用细尺度参数化方法研究了湍流混合在28 kgm-3中性密度面的特征。研究发现在该中性密度面,垂向混合率达到(1.13±0.14)×10-4 m2s-1,比开阔大洋中的扩散率大一个量级。这里强混合的形成有多方面因素,一方面上层强烈的西风带输入大量能量,另一方面在深层海洋,强劲的南极绕极流与地形的相互作用为内波场提供能量。此外,MOC的下支流环通过28 kgm-3中性密度面的向MOC上支流环的体积输送可以达到4.8±0.6 Sv,是冷水下沉到MOC下支流环的体积的一半之多。而经向翻转环流的下支控制着深海中的水体、热量、C02以及营养物质的输送,这对估计全球的气候和生物化学变化过程有着重要的价值。
[Abstract]:The internal wave is a kind of wave which exists in the stable stratified ocean and affects the quality of the ocean. Transport of momentum and energy. The nonlinear interaction between internal waves transfers energy from large scale to small scale, which results in the breakup of internal waves. Turbulent mixing across the isodensity surface. Small-scale turbulent mixing for heat transport, vertical transport of water exchange and dissolved substances (nutrients and pollutants), and global climate. Thermohaline circulation, changes in the marine environment and ecosystems have important effects. It is of great significance to study the temporal and spatial characteristics of turbulent mixing and its influencing factors. The turbulence mixing in the ocean is mainly caused by the breakup of internal waves, and a large number of studies show that wind generated near inertial energy. Tides and the interaction between currents and seabed topography (especially in the Southern Ocean) are the main sources of energy in the internal wave field. Japan Oceanographic Data Center and KESS Program (. Kuroshio Extension System study (Kuroshio Extension System study), conductivity-temperature-depth. Based on the data of CTD hydrological profile, the temporal and spatial variation of cross isodensity surface in the Northwest Pacific is studied based on the method of fine scale parameterization. It is found that the turbulence mixing between 300m and 1800m in the upper ocean has a significant seasonal variation and is statistically correlated with the wind-generated near inertial energy: relative to the smooth terrain. The turbulent mixing coefficient is strengthened in the rough terrain. The turbulent mixing enhanced by wind generated near inertial energy and rough submarine topography can penetrate to the interior of the ocean 1800m and to the sea floor 3300m respectively. The penetration distance varies with wind generated near inertial energy and terrain roughness. This study proves that the driving of wind-generated near-inertial energy and the influence of submarine topography are important for maintaining turbulent mixing in the ocean. The mixing process of the deep sea causes the cold water of the deep sea to rise to the upper layer of the ocean. Thus the meridional Overturning circulation (MOC) is closed in the Southern Ocean. The 28 kgm-3 neutral density surface can be used as an interface between the upper and lower layers of meridional reversal circulation. Antarctic Circumpolar Current. ACCA area. This article combines Argo Array for Real-time Geostrophic Oceanographywith DIMES (. Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean. The CTD profile data in. The characteristics of turbulent mixing on the 28 kgm-3 neutral density surface are studied by using the fine scale parameterization method. The vertical mixing rate is 1.13 卤0.14) 脳 10 ~ (-4) m ~ (-2) s ~ (-1), which is one order of magnitude higher than that in the open ocean. On the one hand, the strong westerly belt in the upper layer invests a lot of energy, on the other hand, in the deep ocean, the strong interaction between the polar current and the topography provides the energy for the internal wave field. The volume transport of the lower tributary ring of MOC to the tributary ring of MOC through the neutral density surface of 28 kgm-3 can reach 4.8 卤0.6 Sv. It is as much as half the volume of cold water sinking into the lower tributary ring of MOC, and the lower branch of the reverse loop controls the transport of water, heat and nutrients in the deep sea. This is of great value in estimating global climate and biochemical processes.
【学位授予单位】：中国科学院研究生院(海洋研究所)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P731.26

【参考文献】