Transformation and Upwelling of Bottom Water in Fracture Zone Valleys
Transformation and Upwelling of Bottom Water in Fracture Zone Valleys
复制标题
断裂带谷地底水转化与上涌
DOI：
10.1175/jpo-d-19-0021.1
复制
发表时间：
2019
影响因子：
3.5
通讯作者：
Ijichi, T.
中科院分区：
文献类型：
--
作者：
Thurnherr, A. M.;Clément, L.;St. Laurent, L.;Ferrari, R.;Ijichi, T.
关闭底层水的翻转环流需要深海转变为较轻的密度和上升流。在何处以及如何获得浮力以及水向上输送仍然是争论的话题，尤其是因为现有的观测结果通常显示深渊中的湍流水平向下增加，显然意味着平均垂直湍流浮力通量发散（致密化）。在这里，我们综合现有的观察表明，底层水的密度较低，并在断裂带山谷上涌的两侧缓慢扩张的米氏海脊，其中包括一半以上的海底面积在某些地区。断裂带几乎完全充满了向上流动并获得浮力的水，在与海底接触的薄边界层中，山谷水局部转化为较轻的密度，其中浮力通量必须为零以匹配无通量边界条件，在与向下降低的湍流水平相关的较厚层中，低于与水力溢流和临界-跨谷积分，湍流浮力通量在侧壁波峰附近显示最大值，与下面的净收敛一致，该模式对湍流轮廓的垂直结构几乎不敏感，这意味着具有向下减小的湍流水平的层中的浮力通量收敛在其他地方的发散上占主导地位，解释了断裂带山谷中向较轻密度的净转化。我们的结论是，断裂带地形可能会产生控制性的影响，在全球海洋的许多地区的底层水的改造和涌升。
Closing the overturning circulation of bottom water requires abyssal transformation to lighter densities and upwelling. Where and how buoyancy is gained and water is transported upward remain topics of debate, not least because the available observations generally show downward-increasing turbulence levels in the abyss, apparently implying mean vertical turbulent buoyancy-flux divergence (densification). Here, we synthesize available observations indicating that bottom water is made less dense and upwelled in fracture zone valleys on the flanks of slow-spreading midocean ridges, which cover more than one-half of the seafloor area in some regions. The fracture zones are filled almost completely with water flowing up-valley and gaining buoyancy.Locally,valley water is transformed to lighter densities both in thin boundary layers that are in contact with the seafloor, where the buoyancy flux must vanish to match the no-flux boundary condition, and in thicker layers associated with downward-decreasing turbulence levels below interior maxima associated with hydraulic overflows and critical-layer interactions.Integrated across the valley, the turbulent buoyancy fluxes show maxima near the sidewall crests, consistent with net convergence below, with little sensitivity of this pattern to the vertical structure of the turbulence profiles, which implies that buoyancy flux convergence in the layers with downward-decreasing turbulence levels dominates over the divergence elsewhere, accounting for the net transformation to lighter densities in fracture zone valleys. We conclude that fracture zone topography likely exerts a controlling influence on the transformation and upwelling of bottom water in many areas of the global ocean.
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DOI：
--
发表时间：
2017
期刊：
影响因子：
--
作者：
L. Clement;A. Thurnherr;L. S. Laurent
通讯作者：
L. S. Laurent
影响因子：
3.5
作者：
de Lavergne, Casimir;Madec, Gurvan;Garabato, Alberto C. Naveira
通讯作者：
Garabato, Alberto C. Naveira
大洋中脊断裂带的深渊上升流
影响因子：
5.2
作者：
L. Clement;A. Thurnherr
通讯作者：
A. Thurnherr
海洋中的混合和二重平流
DOI：
--
发表时间：
2001
期刊：
影响因子：
--
作者：
Louis Laurent;J. Toole;R. Schmitt
通讯作者：
R. Schmitt
粗略测深以上深渊细尺度运动的时间特征
影响因子：
3.5
作者：
J. Toole
通讯作者：
J. Toole