Major deep‐convection activity in the northwestern Mediterranean during winter 2005 triggered the formation of a complex anomalous deep‐water structure that substantially modified the properties of the Western Mediterranean deep layers. Since then, evolution of this thermohaline structure, the so‐called Western Mediterranean Transition (WMT), has been traced through a regularly sampled hydrographic deep station located on the outer continental slope of Minorca Island. A rapid erosion of the WMT's near‐bottom thermohaline signal was observed during 2005–2007. The plausible interpretation of this as local bottom‐intensified mixing motivates this study. Here, the evolution of the WMT structure through 2005–2007 is reproduced by means of a one‐dimensional diffusion model including double‐diffusive mixing that allows vertical variation of the background mixing coefficient and includes a source term to represent the lateral advection of deep‐water injections from the convection area. Using an optimization algorithm, a best guess for the depth‐dependent background mixing coefficient is obtained for the study period. WMT evolution during its initial stages is satisfactorily reproduced using this simple conceptual model, indicating that strong depth‐intensified mixing (K ^∞ (z) ≈ 22 × 10⁻⁴ m² s⁻¹; z ⪆ 1,400 dbar) is a valid explanation for the observations. Extensive hydrographic and current observations gathered over the continental slope of Minorca during winter 2018, the first deep‐convective winter intensively sampled in the region, provide evidence of topographically localized enhanced mixing concurrent with newly formed dense waters flowing along‐slope toward the Algerian sub‐basin. This transport‐related boundary mixing mechanism is suggested to be a plausible source of the water‐mass transformations observed during the initial stages of the WMT off Minorca.

中文翻译：

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在西地中海过渡初期，持续的深度强化混合

2005年冬季，地中海西北部的主要深对流活动触发了复杂的异常深水结构的形成，该结构大大改变了地中海西部深层的性质。从那时起，通过位于梅诺卡岛外陆斜坡上的定期采样水文深水站，追溯了这种热盐结构的演化，即所谓的西地中海过渡带（WMT）。在2005年至2007年期间，观测到WMT的近底热盐信号迅速衰减。对此的合理解释是局部底部强化混合，这促使了这项研究。这里，2005年至2007年WMT结构的演变是通过一维扩散模型重现的，该模型包括双重扩散混合，该混合允许背景混合系数的垂直变化，并包括代表深水注入的横向对流的源项从对流区域。使用优化算法，可以得出研究期间与深度相关的背景混合系数的最佳猜测。使用此简单的概念模型可以令人满意地重现WMT初始阶段的演变过程，这表明强烈的深度强化混合（在研究期间可以获得与深度相关的背景混合系数的最佳猜测。使用此简单的概念模型可以令人满意地重现WMT初始阶段的演变过程，这表明强烈的深度强化混合（在研究期间可以获得与深度相关的背景混合系数的最佳猜测。使用此简单的概念模型可以令人满意地重现WMT初始阶段的演变过程，这表明强烈的深度强化混合（ķ ^∞（ż）≈22×10 ^-4 米²小号^-1 ; ž ⪆1400 dbar）是观察一个合理的解释。2018年冬季，在米诺卡大陆坡上收集了广泛的水文和当前观测资料，这是该地区第一个密集采样的深对流冬季，提供了地形局部混合增强的证据，同时新形成的稠密水沿着斜坡流向阿尔及利亚次大陆。盆地。该运输相关的边界混合机制被认为是在梅诺卡岛WMT初始阶段观测到的水质转变的合理来源。