Tempo-Spatial Variations of the Kuroshio Current in the Tokara Strait Based on Long-Term Ferryboat ADCP Data
Tempo-Spatial Variations of the Kuroshio Current in the Tokara Strait Based on Long-Term Ferryboat ADCP Data
复制标题
基于长期渡船ADCP数据的吐噶喇海峡黑潮时空变化
DOI：
10.1029/2018jc014771
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发表时间：
2019
影响因子：
3.6
通讯作者：
Dong Menghong
中科院分区：
文献类型：
--
作者：
Liu Zhao-Jun;Nakamura Hirohiko;Zhu Xiao-Hua;Nishina Ayako;Guo Xinyu;Dong Menghong
介绍了 2003 年至 2012 年期间渡船声学多普勒海流剖面仪测量的吐噶喇海峡黑潮的横向-垂直结构和时间变化，水平分辨率为 2 公里，间隔为两天。穿过吐噶喇海峡的黑潮呈现出多核速度结构。相对于 700 m 的斜压成分，其季节性体积运输变化是一年两次，在 7 月和 12 月至 1 月达到峰值。然而，正压输送成分表现出年度周期，在 12 月达到最大值。对截面速度进行经验正交函数分析。前两个经验正交函数模态分别揭示了黑潮洋流轴的南北移动和黑潮体积输送的变化。前两个模态的时间变化分别对应于黑潮位置指数和海峡两岸海平面差的时间变化。第三种经验正交函数模式具有相对较小的水平尺度，在湍流混合方面进行了研究。这种模式捕获的带状结构可能是由流-地形相互作用引起的，因为黑潮路线中的岛屿可能导致水平和垂直流分离。基于高分辨率再分析数据的附加分析表明，（1）在埃尔特尔位涡为负的区域中预计会出现惯性不稳定，从而增强吐噶喇海峡岛屿周围的垂直混合；（2）当黑潮直接撞击岛屿时，岛屿背风处的流散度会驱动上升流并导致等温线抬升。
Transverse‐vertical structure and temporal variability of the Kuroshio current across the Tokara Strait during 2003–2012 measured by a ferryboat acoustic Doppler current profiler with a 2‐km horizontal resolution and a two‐day interval are presented. The Kuroshio passing through the Tokara Strait exhibits a multicore velocity structure. Its seasonal volume transport variation is biannual for baroclinic components relative to 700 m, peaking in July and December–January. However, the barotropic transport component exhibits an annual cycle with a maximum in December. Empirical orthogonal function analysis of the cross‐sectional velocity is performed. The first two empirical orthogonal function modes reveal the north‐south shift of the Kuroshio current axis and the change in Kuroshio volume transport, respectively. Temporal variabilities of the leading two modes correspond to those of the Kuroshio Position Index and the sea level difference across the strait, respectively. The third empirical orthogonal function mode, with a relatively smaller horizontal scale, was examined in terms of turbulent mixing. The banded structure captured by this mode is likely induced by flow‐topography interaction because islands in the Kuroshio route could cause horizontal and vertical flow separation. Additional analysis based on high‐resolution reanalysis data suggested that (1) inertial instability, which is expected in the areas with negative Ertel's potential vorticity, arises to enhance vertical mixing around the islands in the Tokara Strait, and (2) when the Kuroshio directly impinges the islands, flow divergence in the lee of the islands drives upwelling and leads to uplift of isotherms.