Based on satellite and in situ data, the dynamic characteristics and vertical structure of a surface intensified mesoscale eddy dipole recently expelled from the South East Madagascar Current (SEMC) is described for the first time. The dipole was surveyed 250 nautical miles south of Madagascar between 14 and 23 November 2016, during west-east and south-north transects carried out over the northern Madagascar Ridge. The dipole consisted of two counter-rotating vortices of similar size (100 km) and intensity (0.7 f), and an intense southwestward jet (150 cm s^-1) in the frontal region between the two eddies. The cyclonic eddy was lying on the western side of the anticyclonic eddy. With azimuthal velocities reaching 100 cm s^-1 at the surface and decreasing slowly with depth (40 cm s^-1 at -600 m), this dipole was defined as a highly non-linear (Ro ~ 0.7) isolated eddy-type structure (c_β ~ 11 cm s^–1 and U/c_β ~ 0.7) capable of trapping and advecting water masses over large distances. The enhanced concentration of chlorophyll-a found in the cyclone relative to the anticyclone could be tracked back to the spin-up phase of the two eddies and attributed to eddy-pumping. The eddy cores were located above the pycnocline (1026.4 kg m^-3), within the upper 600 m, and consisted of varieties of Subtropical Underwater (STUW) found within the SEMC. The STUW found in the anticyclone was more saline and oxygenated than in the cyclone, highlighting mixing with the inshore shelf waters from the southeastern coastal upwelling cell off Madagascar. Observations suggest that the dipole interacted strongly with the chaotic bathymetry of the region, characterized by a group of five seamounts lying between -240 m and -1200 m. The bathymetry blocked its westward advection, trapping it in the vicinity of one shallow seamount for more than 4 weeks, so enhancing the role of the eddy-induced velocities in stirring the surrounding water masses. Squeezed between the southern Madagascan shelf and the northern flank of the anticyclone, two filament-like dynamic features with very different water-mass properties could be observed on the south-north transect: i) one filament highly concentrated in chlorophyll-a demonstrating the capacity of the eddy to export shelf water offshore; ii) intrusions of southern-type STUW generally found south of the South Indian Counter Current (SICC) recirculating on the external flanks of the anticyclone. Although the observed circulation and hydrography were largely constrained by the presence of the mesoscale eddy dipole, unmistakable fine-scale dynamics were also observed in the vicinity of the MAD-Ridge seamount, superimposed onto the mesoscale eddy flow.

基于卫星和原位数据，首次描述了最近从东南马达加斯加洋流（SEMC）驱逐出的表面增强的中尺度涡流偶极子的动力学特性和垂直结构。2016年11月14日至23日，在马达加斯加洋脊北部进行东西向和南北向横断面测量期间，对偶极子进行了调查，距离马达加斯加以南250海里。偶极子由两个大小相似（100 km）和强度（0.7 f）的反向旋转涡旋组成，并且在两个涡流之间的额叶区域中有一个强烈的西南向射流（150 cm s ^-1）。旋风涡旋位于反旋风涡旋的西侧。方位角速度达到100 cm s ^-1在表面处，并与深度缓慢下降（40厘米小号^-1 在-600米），这偶极被定义为高度非线性的（滚装〜0.7）分离涡型结构（ç _β  〜11厘米小号^{- 1}和ú / ç _β  〜0.7）能够俘获和在大的距离平流输送水团。叶绿素的浓度提高一个相对于所述反气旋旋风分离器中发现的可以追踪回两个旋涡的旋转加速阶段和归因于涡抽。涡流核心位于比诺可林上方（1026.4 kg m ^-3），在600 m以内，由SEMC内的亚热带水下（STUW）变种组成。与旋风分离器相比，在反旋风分离器中发现的STUW的盐分和含氧量更高，突显出与马达加斯加东南沿海上升流单元的近海陆架水混合。观测结果表明，偶极子与该区域的混沌测深法有很强的相互作用，其特征是一组位于-240 m至-1200 m之间的五个海山。该测深法阻止了它的向西平流，将其困在一个浅海山附近超过4周，因此增强了涡旋速度在搅动周围水团中的作用。挤在马达加斯加南部的架子和反旋风的北部之间，一个示范的涡到出口货架水近海的能力; ii）南部型STUW的入侵通常发现在南印度逆流（SICC）的南部，在反气旋的外侧面循环。尽管观测到的循环和水文学在很大程度上受到中尺度涡流偶极子的约束，但在MAD-Ridge海山附近也观察到了明显的精细尺度动力学，这些动力学叠加在中尺度涡流上。