Mapping turbulent diffusivity associated with oceanic internal lee waves offshore Costa Rica
Mapping turbulent diffusivity associated with oceanic internal lee waves offshore Costa Rica
复制标题
绘制与哥斯达黎加近海海洋内背风波相关的湍流扩散率
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
R. Schmitt
中科院分区：
文献类型：
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作者：
W. Fortin;W. Holbrook;R. Schmitt
抽象的。破碎内波在维持纬向翻转环流中起主要作用。海洋背风波是一个显着的贡献者diapycnal混合相关的内波耗散，但直接测量是困难的标准海洋采样方法，由于有限的空间范围内的驻波背风波。在这里，我们提出了一个分析的海洋内部背风波观测近海哥斯达黎加东部使用地震成像和估计的湍流扩散率通过一个新的地震斜率谱方法，直接从地震图像中提取扩散率，使用跟踪反射只缩放扩散率值。结果提供了整个水柱的湍流扩散系数在几百米的横向和10米的垂直尺度的估计。合成测试表明，该方法的能力，解决湍流结构和重现准确的扩散系数。我们在西加勒比地区的地震剖面的湍流图显示，在粗糙的海底地形附近以及在观测到的背风波传播终止的中间水柱中，湍流扩散率升高。中层水柱热点的湍流扩散率水平比周围沃茨水域高5倍，比典型的公海扩散率高50倍。这个地点有稳定的电流，使其成为研究背风波产生，传播和衰减的特别容易的实验室。
Abstract. Breaking internal waves play a primary role in maintaining the meridional overturning circulation. Oceanic lee waves are known to be a significant contributor to diapycnal mixing associated with internal wave dissipation, but direct measurement is difficult with standard oceanographic sampling methods due to the limited spatial extent of standing lee waves. Here, we present an analysis of oceanic internal lee waves observed offshore eastern Costa Rica using seismic imaging and estimate the turbulent diffusivity via a new seismic slope spectrum method that extracts diffusivities directly from seismic images, using tracked reflections only to scale diffusivity values. The result provides estimates of turbulent diffusivities throughout the water column at scales of a few hundred meters laterally and 10 m vertically. Synthetic tests demonstrate the method's ability to resolve turbulent structures and reproduce accurate diffusivities. A turbulence map of our seismic section in the western Caribbean shows elevated turbulent diffusivities near rough seafloor topography as well as in the mid-water column where observed lee wave propagation terminates. Mid-water column hotspots of turbulent diffusivity show levels 5 times higher than surrounding waters and 50 times greater than typical open-ocean diffusivities. This site has steady currents that make it an exceptionally accessible laboratory for the study of lee-wave generation, propagation, and decay.