A view of the Brazil-Malvinas confluence, March 2015
A view of the Brazil-Malvinas confluence, March 2015
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DOI：
10.1016/j.dsr.2021.103533
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发表时间：
2021-05-13
影响因子：
2.4
通讯作者：
Vidal, Montserrat
中科院分区：
文献类型：
--
作者：
Orue-Echevarria, Dorleta;Pelegri, Josep L.;Vidal, Montserrat
亚热带巴西流(BC)和亚北极马尔维纳斯流(MC)沿阿根廷盆地西缘相遇，形成了巴西-马尔维纳斯交汇处(BMC)，这是世界海洋中最强烈的开阔洋锋之一，也是形成中间水团的场所。在这里，我们根据2015年3月收集的物理和生物地球化学数据--水文站、剖面浮游物和地下漂浮物--对BMC进行全面描述。我们使用这些数据来描述撞击和流出的洋流，并描述交叉和沿锋面的温盐结构。此外，我们还将现场测量结果与气候资料和墨卡托海洋涡旋再分析资料进行了比较。水道剖面显示了两个西部边界流之间的对比性质：由BC向南输送的温暖、含盐、营养和缺氧的少营养亚热带水域，以及由MC向北输送的寒冷、淡水、富含氧气和营养的亚南极水域。锋面系统的特征还包括温盐侵入的存在，随着碰撞的洋流塑造锋面系统，跨锋面梯度和沿锋速度变得尖锐。我们还观察到锋面急流顶部扩散的微咸水，这是东北风有利的汇合动力和场外平流的结果。这些低盐度水域与锋面急流上的地表非地转速度呈正相关。巡航数据说明了与气候条件相比区域和中尺度的高度可变性，并进一步记录了次中尺度次表层的复杂性，而现有的业务模式没有适当地捕捉到这种复杂性。
The encountering of the subtropical Brazil Current (BC) and the subantarctic Malvinas Current (MC) along the western margin of the Argentine Basin forms the Brazil-Malvinas Confluence (BMC), one of the most intense open-ocean fronts in the world ocean and a site for the formation of intermediate water masses. Here, we provide a comprehensive description of the BMC based on physical and biogeochemical data - hydrographic stations, profiling floats and subsurface drifters - gathered in March 2015. We use these data in order to characterize the impinging and outflowing currents and to describe the cross- and along-frontal thermohaline structure. In addition, we compare the in-situ measurements with both climatological data and the Mercator Ocean eddyresolving reanalysis. The hydrographic sections illustrate the contrasting properties between the two western boundary currents: warm, salty, nutrient- and oxygen-poor oligotrophic subtropical waters carried southward by the BC and the cold, fresh, oxygen- and nutrient-rich subantarctic waters carried northward by the MC. The frontal system is also characterized by the presence of thermohaline intrusions, with the cross-frontal gradients and along-front velocities sharpening as the colliding currents shape the frontal system. We also observe brackish waters spreading on top of the frontal jet as a result of both the confluence dynamics and off-shelf advection favored by north-easterly winds. These low-salinity waters are positively correlated with surface ageostrophic speeds over the frontal jet. The cruise data illustrates the high regional and mesoscale variability as compared with climatological conditions, and further document the submesoscale subsurface complexity, which is not properly captured by available operational models.