Warm Spiral Streamers over Gulf Stream Warm-Core Rings
Warm Spiral Streamers over Gulf Stream Warm-Core Rings
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DOI：
10.1175/jpo-d-20-0035.1
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发表时间：
2020-11
影响因子：
3.5
通讯作者：
W. Zhang;D. McGillicuddy
中科院分区：
文献类型：
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作者：
W. Zhang;D. McGillicuddy
本研究探讨了墨西哥湾流暖核环的暖螺旋结构（这里称为螺旋飘带）的产生。卫星海洋表面温度图像显示，墨西哥湾流或新形成的暖心环的暖水撞击旧的暖心环，然后侵入旧的环后形成螺旋流。2018年4月的实地测量捕获了温暖螺旋流的垂直结构，作为低密度水缠绕在旧环上的浅透镜。观测还显示，螺旋状流光的两侧都发生了俯冲，将表面沃茨向下携带。理想化的数值模式模拟初始化所观察到的水团密度再现螺旋流在暖核环，并揭示它们的形成是一个非线性的亚中尺度过程中尺度动力学强迫。入侵水的负密度异常在入侵水与地表环水界面处形成密度锋，通过热成风平衡，驱动局部反气旋流。局部界面流的压力梯度和动量平流将入侵水推向环中心。环的大尺度反气旋流动和侵入水的径向运动共同形成螺旋流光。观察到的俯冲两侧的螺旋拖缆是二次交叉拖缆环流的一部分，从伸展拖缆边缘的锋生。二次环流的表面辐散推动流光的侧边彼此远离，加宽了表面上的暖螺旋，从而增强了其表面信号。
This study examines the generation of warm spiral structures (referred to as spiral streamers here) over Gulf Stream warm-core rings. Satellite sea surface temperature imagery shows spiral streamers forming after warmer water from the Gulf Stream or newly formed warm-core rings impinges onto old warm-core rings and then intrudes into the old rings. Field measurements in April 2018 capture the vertical structure of a warm spiral streamer as a shallow lens of low-density water winding over an old ring. Observations also show subduction on both sides of the spiral streamer, which carries surface waters downward. Idealized numerical model simulations initialized with observed water-mass densities reproduce spiral streamers over warm-core rings and reveal that their formation is a nonlinear submesoscale process forced by mesoscale dynamics. The negative density anomaly of the intruding water causes a density front at the interface between the intruding water and surface ring water, which, through thermal wind balance, drives a local anticyclonic flow. The pressure gradient and momentum advection of the local interfacial flow push the intruding water toward the ring center. The large-scale anticyclonic flow of the ring and the radial motion of the intruding water together form the spiral streamer. The observed subduction on both sides of the spiral streamer is part of the secondary cross-streamer circulation resulting from frontogenesis on the stretching streamer edges. The surface divergence of the secondary circulation pushes the side edges of the streamer away from each other, widens the warm spiral on the surface, and thus enhances its surface signal.