Deepwater dynamics and mixing processes during a major inflow event in the central Baltic Sea
Deepwater dynamics and mixing processes during a major inflow event in the central Baltic Sea
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DOI：
10.1002/2017jc013050
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发表时间：
2017-08-01
影响因子：
3.6
通讯作者：
Umlauf, Lars
中科院分区：
文献类型：
--
作者：
Holtermann, Peter L.;Prien, Ralf;Umlauf, Lars
在所谓的波罗的海主要流入（MBI）期间，大量密集和富氧沃茨的侵入形成了波罗的海翻转环流和深水通风的重要组成部分。尽管它们的重要性，但是，在MBI期间发生在中央盆地的过程的详细观测几乎是缺乏的。这里提供了位于其中一个主要盆地中心的自主剖面测量平台的长期部署数据，首次直接详细地了解了有史以来最大的MBI（MBI 2014/2015）引起的深水修改和动态。大约，21 Gmol的氧气进口在三个不同的流入阶段，在中间深度的氧化侵入体的意外大的贡献。在滞流期间的氧消耗率紧随流入阶段被认为是87克米（-2）年（-1）的沉积物的需氧量的主要贡献。最具活力的深水过程（地形波和近惯性波）仅受到流入的轻微影响;然而，与侵入体和涡流相关的亚惯性能级大大增强。湍流微观结构数据显示，即使在MBI的充满活力的条件下，深内部区域基本上保持非湍流，强调边界混合的重要性。温暖的侵入体经常表现出温度精细结构的垂直尺度为0.1米的顺序，没有任何迹象的积极动荡。在这些侵入体的上侧翼，经常发现双扩散楼梯的发展，这表明在流入条件下的一个重要的替代混合过程。
Intrusions of large amounts of dense and oxygen-rich waters during so-called Major Baltic Inflows (MBIs) form an essential component of the Baltic Sea overturning circulation and deepwater ventilation. Despite their importance, however, detailed observations of the processes occurring in the central basins during an MBI are virtually lacking. Here data from a long-term deployment of an autonomous profiling platform located in the center of one of the main basins are presented, providing the first direct and detailed view of the deepwater modifications and dynamics induced by one of the largest MBIs ever recorded (MBI 2014/2015). Approximately, 21 Gmol of oxygen were imported during three distinct inflow phases with an unexpectedly large contribution of oxic intrusions at intermediate depth. Oxygen consumption rates during the stagnation period immediately following the inflow phase was found to be 87 g m(-2) yr(-1) with a dominant contribution of sedimentary oxygen demand. The most energetic deepwater processes (topographic and near-inertial waves) were only marginally affected by the inflow; however, subinertial energy levels associated with intrusions and eddies were strongly enhanced. Turbulence microstructure data revealed that the deep interior regions remain essentially nonturbulent even during the energetic conditions of an MBI, emphasizing the importance of boundary mixing. Warm intrusions frequently showed a temperature fine structure with vertical scales of the order of 0.1 m, without any signs of active turbulence. At the upper flanks of these intrusions, double-diffusive staircases were often found to develop, suggesting an important alternative mixing process during inflow conditions.