Energetic subsurface eddies (SSEs) play a significant role in regulating the subthermocline circulation east of the Philippines. However, due to the paucity of targeted observations, they remain largely unexplored. By analyzing the outputs from an eddy-resolving ocean general circulation model (OGCM), this study investigated the statistics of SSEs east of the Philippines, including their geographic characteristics, vertical structures, and eddy-induced transport. During the period of 2009–2019, approximately 1927 and 1176 SSEs were detected to be anticyclonic and cyclonic, respectively, indicating the predominance of subsurface anticyclonic eddies (SSAE). The hotspot area of SSEs is in the latitude band of 6° N–15° N off the Philippine coast, especially around 10° N and 14° N–15° N prevailing abundant SSEs. Most SSEs originate at ∼138° E furthest with a mean lifespan of 55 days and a westward translation speed of 6 cm/s. The composite SSAE exhibits a typical subsurface-intensified feature with a velocity core at ∼520 m, while the subsurface cyclonic eddy (SSCE) has a relatively shallow core at ∼420 m and exhibits considerable strength near the surface with a rotating speed is around 5 cm/s. Temperature anomalies induced by SSEs show a dual-core structure associated with lens-like isopycnal undulations, and salinity anomalies are characterized by an alternating positive and negative signal owing to the complexity of the water masses. SSEs-induced meridional volume transport mainly occurs off the Philippine coast, where the northward transport is approximately 0.3 Sv and the southward transport is approximately 0.5 Sv. The zonal volume transport of SSEs is 1–2 Sv per latitude and mainly occurs in the North Equatorial Current (NEC) region. SSEs-induced stirring heat/salt transport is 1–2 orders larger than the trapping component and is mainly concentrated near the Mindanao coast. The meridional stirring heat transport is equatorward, which is up to 2.7 × 10 W/m, and the salt transport is northward with a magnitude of ∼100 kg·m·s between 200 m and 2000 m. At the 8°N section, the mean salt transport associated with SSEs is about 24% of that induced by the Mindanao Undercurrent (MUC).

中文翻译：

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菲律宾东部的地下涡流：地理特征、垂直结构、体积和温盐输送

高能次表层涡流（SSE）在调节菲律宾东部的次温跃层环流方面发挥着重要作用。然而，由于缺乏有针对性的观察，它们在很大程度上仍未得到探索。通过分析涡旋解析海洋环流模型（OGCM）的输出，本研究调查了菲律宾东部SSE的统计数据，包括其地理特征、垂直结构和涡流引起的输送。2009年至2019年期间，分别检测到大约1927个和1176个SSE是反气旋性和气旋性的，表明地下反气旋涡流（SSAE）占主导地位。南海风暴的热点区域是菲律宾海岸外的北纬6°~15°北纬，尤其是北纬10°和北纬14°~15°左右，南海风暴最为丰富。大多数SSE最远起源于东经138°，平均寿命为55天，向西平移速度为6厘米/秒。复合SSAE表现出典型的次表层强化特征，其速度核心位于~520 m，而次表层气旋涡流（SSCE）在~420 m处具有相对较浅的核心，并且在近地表处表现出相当大的强度，转速约为5厘米/秒。SSE引起的温度异常表现出与透镜状等密度波动相关的双核结构，而由于水团的复杂性，盐度异常的特征是正负信号交替。SSE引起的经向体积输送主要发生在菲律宾沿海，向北输送量约为0.3 Sv，向南输送量约为0.5 Sv。SSE 的纬向体积输送量为每个纬度 1-2 Sv，主要发生在北赤道流 (NEC) 地区。SSE 引起的搅拌热/盐传输比捕集成分大 1-2 个数量级，主要集中在棉兰老岛海岸附近。经向搅拌热传输方向为赤道方向，高达2.7×10 W/m；盐传输方向为北方向，在200 m至2000 m之间，量级约为100 kg·m·s。在北纬 8° 部分，与 SSE 相关的平均盐输送量约为棉兰老岛暗流 (MUC) 引起的盐输送量的 24%。