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首页> 外文期刊>Journal of Physical Oceanography >Seismic Imaging of Rapid Onset of Stratified Turbulence in the South Atlantic Ocean*
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Seismic Imaging of Rapid Onset of Stratified Turbulence in the South Atlantic Ocean*

机译：南大西洋快速发生分层湍流的地震成像*

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Broadband measurements of the internal wavefield will help to unlock an understanding of the energy cascade within the oceanic realm. However, there are challenges in acquiring observations with sufficient spatial resolution, especially in horizontal dimensions. Seismic reflection profiling can achieve a horizontal and vertical resolution of order meters. It is suitable for imaging thermohaline fine structure on scales that range from tens of meters to hundreds of kilometers. This range straddles the transition from internal wave to turbulent regimes. Here, the authors analyze an 80-km-long seismic image from the Falkland Plateau and calculate vertical displacement spectra of tracked reflections. First, they show that these spectra are consistent with the Garrett-Munk model at small horizontal wavenumbers (i.e., k(x) less than or similar to 3 x 10(-3) cpm). There is a transition to stratified turbulence at larger wavenumbers (i.e., k(x) greater than or similar to 2 x 10(-1) cpm). This transition occurs at length scales that are significantly larger than the Ozmidov length scale above which stratification is expected to modify isotropic Kolmogorov turbulence. Second, the authors observe a rapid onset of this stratified turbulence over a narrow range of length scales. This onset is consistent with a characteristic energy injection scale of stratified turbulence with a forward cascade toward smaller scales through isotropic turbulence below the Ozmidov length scale culminating in microscale dissipation. Finally, they estimate the spatial pattern of diapycnal diffusivity and show that the existence of an injection scale can increase these estimates by a factor of 2.
机译：内部波场的宽带测量将有助于解锁对海洋领域内能量级联的理解。但是，在获取具有足够空间分辨率的观测数据时尤其是在水平方向上存在挑战。地震反射轮廓分析可以实现阶米的水平和垂直分辨率。它适合在数十米到几百公里范围内对热盐精细结构进行成像。该范围跨越了从内部波浪到湍流状态的过渡。在这里，作者分析了一个来自福克兰高原的80公里长的地震图像，并计算了跟踪反射的垂直位移谱。首先，他们表明这些光谱在较小的水平波数（即k（x）小于或类似于3 x 10（-3）cpm）下与Garrett-Munk模型一致。在更大的波数（即大于或等于2 x 10（-1）cpm的k（x））处存在到分层湍流的过渡。这种转变发生在明显大于Ozmidov长度尺度的长度尺度上，在该尺度之上，分层有望改变各向同性的Kolmogorov湍流。其次，作者观察到这种分层湍流在狭窄的长度范围内迅速发作。这种发作与分层湍流的特征能量注入尺度相一致，通过在Ozmidov长度尺度以下的各向同性湍流朝着更小尺度的向前级联，最终达到了小尺度，最终导致了微观尺度的耗散。最后，他们估算了二面体扩散系数的空间模式，并表明注射规模的存在可使这些估算值增加2倍。

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