Spatiotemporal Characteristics and Volume Transport of Lagrangian Eddies in the Northwest Pacific
Spatiotemporal Characteristics and Volume Transport of Lagrangian Eddies in the Northwest Pacific
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DOI：
10.3390/rs15174355
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发表时间：
2023-09
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影响因子：
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通讯作者：
Quanmu Yuan;Jianyu Hu
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文献类型：
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作者：
Quanmu Yuan;Jianyu Hu
中尺度涡旋在物质、热量、盐份和营养物质的输送中起着至关重要的作用，对海洋环流模式、海洋地球化学过程和全球气候系统产生重要影响。利用1993-2019年27 a的地转流资料，基于拉格朗日平均涡度偏差（LAVD）方法，对西北太平洋（NWP; 10°N-30°N，115°E-155°E）的旋转相干拉格朗日涡（RCLVs）进行了探测，并比较了欧拉海平面高度涡（SSH涡）和RCLVs的时空特征。春季和冬季可以观测到较多的SSH涡旋和RCLV，且其年际变化相似。SSH涡旋在副热带逆流区具有较高的生成数和较大的半径，而RCLV更有利于在海洋盆地中发生。两种涡旋类型的传播速度分布几乎相同，并随着纬度的增加而减小。由于RCLV在有限时间内维持的物质相干输运，与SSH涡旋相比，RCLV的相干核在尺度上要小得多。SSH涡旋和RCLV引起的平均纬向输送估计分别为-0.82 Sv和-0.51 Sv（1 Sv = 106 m3/s）。对于具有RCLV的非重叠SSH涡流，涡流内约80%的水在涡流的寿命期间泄漏。在重叠SSH涡的情况下，涡内相干水的比例随着半径的增加而减小，泄漏率约为58%。最后，对吕宋海峡附近黑潮的36个RCLV脱落事件进行了检查，这些事件引起了平均-0.14 Sv的纬向输送，揭示了54%的脱落RCLV内的水来自黑潮。
Mesoscale eddies play a crucial role in the transport of mass, heat, salt and nutrients, exerting significant influence on ocean circulation patterns, biogeochemical processes and the global climate system. Based on Lagrangian-Averaged Vorticity Deviation (LAVD) method, this study applies 27 years (1993–2019) of geostrophic current velocity data to detect Rotationally Coherent Lagrangian Vortices (RCLVs) in the Northwest Pacific (NWP; 10°N–30°N, 115°E–155°E), with the spatiotemporal characteristics of Eulerian Sea Surface Height Eddies (SSH eddies) and RCLVs being compared. A higher number of SSH eddies and RCLVs can be observed in spring and winter, and their inter-annual variations are similar. SSH eddies show higher generation number and larger radius in the Subtropical Countercurrent region, while RCLVs occur more favorably in the ocean basin. The propagation speed distributions of both eddy types are nearly identical and decrease with increasing latitude. Due to the material coherent transport maintained by RCLVs within a finite time interval, the coherent cores of RCLVs are considerably smaller in scale as compared to those of SSH eddies. The average zonal transports induced by SSH eddies and RCLVs are estimated to be −0.82 Sv and −0.51 Sv (1 Sv = 106 m3/s), respectively. For non-overlapping SSH eddies with RCLVs, approximately 80% of the water within the eddy leaks out during the eddy’s lifespan. In the case of overlapping SSH eddies, the ratio of coherent water inside the eddy decreases with increasing radius, and the leakage rate is around 58%. Finally, an examination of 36 shedding RCLVs events from the Kuroshio near the Luzon Strait, which induce an average zonal transport of −0.14 Sv, reveals that 54% of the water within the shedding RCLVs originates from the Kuroshio.