Observation of Near-inertial Waves in the Bottom Boundary Layer of an Abyssal Seamount
Observation of Near-inertial Waves in the Bottom Boundary Layer of an Abyssal Seamount
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深海海山底部边界层近惯性波的观测
DOI：
10.1175/jpo-d-22-0026.1
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发表时间：
2022-12
影响因子：
3.5
通讯作者：
Jiannan Wang
中科院分区：
文献类型：
--
作者：
Xiaohui Xie;Yan Wang;Zhiyu Liu;Xiaohui Liu;Dake Chen;Dongsheng Zhang;Jiannan Wang
摘要：底边界层对深海低频流的全球能量耗散有重要贡献，但这种能量耗散是如何发生的，目前还知之甚少。利用在西太平洋深海海山边界边界附近收集的现场资料，我们证明了倾斜地形上的强底陷气流可以将能量损失到通过调整底部Ekman层而产生的近惯性波(NIW)。观测到了与传播方向平行于地形坡度的内波对应的近共振频率的NIW。这些波在边界层中是最强的，并与海山外的亚惯性流有关，这在很大程度上归因于海山上空的底陷反气旋环流驱动的Ekman输送。观测到底部强化的NIW具有主要的向上传播能量，并假设它是通过边界层中Ekman流-地形相互作用产生的。结果表明，近底流到辐射NIW的能量损失(~8×10−4W/m2)比底阻耗散(~2×10−4W/m2)大得多，表明通过埃克曼输运调节产生的内波在抑制倾斜海底的亚惯性流中起着重要作用。
Abstract.The bottom boundary layer (BBL) contributes significantly to the global energy dissipation of low-frequency flows in the abyssal ocean, but how this dissipation occurs remains poorly understood. Using in-situ data collected near the BBL at an abyssal seamount in the western Pacific Ocean, we demonstrate that strong bottom-trapped flows over sloping topography can lose their energy to near-inertial waves (NIWs) generated via the adjustment of the bottom Ekman layer. The NIWs with near-resonant frequencies corresponding to internal waves with propagation direction parallel to the topographic slope are observed. These waves are strongest in the BBL and have a correlation with the off-seamount sub-inertial flows largely attributed to the Ekman transport driven by the bottom-trapped anticyclonic circulation over the seamount. The bottom-intensified NIWs are observed to have dominant upward propagating energy and hypothesized to be generated via Ekman flow-topography interactions in the BBL. Energy loss from the near-bottom flows to radiating NIWs (~8 × 10−4 W/m2) is estimated to be substantially larger than that due to bottom drag dissipation (~2 × 10−4 W/m2), suggesting the important role of internal wave generation via the Ekman transport adjustment in damping the sub-inertial flows over the sloping seafloor.