Tropical Instability Waves and Wind‐Forced Cross‐Equatorial Flow in the Central Atlantic Ocean
Tropical Instability Waves and Wind‐Forced Cross‐Equatorial Flow in the Central Atlantic Ocean
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DOI：
10.1029/2022gl099325
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发表时间：
2022-09
影响因子：
5.2
通讯作者：
F. Heukamp;P Brandt;M. Dengler;F. Tuchen;M. Mcphaden;J. Moum
中科院分区：
文献类型：
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作者：
F. Heukamp;P Brandt;M. Dengler;F. Tuchen;M. Mcphaden;J. Moum
基于位于0°N，23°W的长期停泊观测站的速度数据，我们提出了赤道大西洋向北和向南上层洋流季节内最大值期间垂直不对称的证据。向北流动期间的特点是接近表面的速度最大值，而向南的阶段显示在约40米处的地下速度最大值。我们发现，所观察到的不对称性是由当地的风。赤道的南风应力驱动地表附近的向北流动和地表以下的向南流动，并叠加在热带不稳定波（TIW）速度场上。这个由风驱动的翻转单元，被称为赤道滚转，显示出与东南信风的纬向分量的季节性相关的明显的季节性周期。赤道横滚和TIW的垂直切变的叠加导致了南北向TIW位相的不对称混合。
Based on velocity data from a long‐term moored observatory located at 0°N, 23°W we present evidence of a vertical asymmetry during the intraseasonal maxima of northward and southward upper‐ocean flow in the equatorial Atlantic Ocean. Periods of northward flow are characterized by a meridional velocity maximum close to the surface, while southward phases show a subsurface velocity maximum at about 40 m. We show that the observed asymmetry is caused by the local winds. Southerly wind stress at the equator drives northward flow near the surface and southward flow below that is superimposed on the Tropical Instability Wave (TIW) velocity field. This wind‐driven overturning cell, known as the Equatorial Roll, shows a distinct seasonal cycle linked to the seasonality of the meridional component of the south‐easterly trade winds. The superposition of vertical shear of the Equatorial Roll and TIWs causes asymmetric mixing during northward and southward TIW phases.