Deep Currents in the Rift Valley of the North Mid-Atlantic Ridge
Deep Currents in the Rift Valley of the North Mid-Atlantic Ridge
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DOI：
10.3389/fmars.2019.00597
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发表时间：
2019-09-20
影响因子：
3.7
通讯作者：
Roullet, Guillaume
中科院分区：
文献类型：
--
作者：
Lahaye, Noe;Gula, Jonathan;Roullet, Guillaume
在大洋中脊，海流与地形之间的相互作用产生复杂的流动，驱动生物地球化学成分的迁移特性，特别是与热液喷口有关的生物地球化学成分，从而影响相关的生态系统。本文介绍了在裂谷沿着亚速尔群岛部分的北大西洋中脊，使用的几个调查和现实的高分辨率模拟的现场数据相结合的环流。它证实了平均深电流的存在，沿山谷的右内翼（向下游看）有一个增强的山谷上分支，沿沿着相反翼在较浅的深度有一个较弱的山谷下分支。裂谷水的水文特性，特别是沿谷密度梯度，结果从地形隔离，深流和相关的混合相结合，进行量化。我们还表明，深电流表现出显着的变化，可以是局部强烈的，典型值大于10厘米/秒。最后，使用数值模拟的动力学强迫的深电流和它们的变化的见解提供，表明潮汐强迫的平均环流是重要的，上覆的中尺度湍流触发大部分的变化。
Over mid-ocean ridges, the interaction between the currents and the topography gives rise to complex flows, which drive the transport properties of biogeochemical constituents, and especially those associated with hydrothermal vents, thus impacting associated ecosystems. This paper describes the circulation in the rift valley along the Azores sector of the North Mid-Atlantic Ridge, using a combination of in-situ data from several surveys and realistic high-resolution modeling. It confirms the presence of a mean deep current with an up-valley branch intensified along the right inner flank of the valley (looking downstream), and a weaker down-valley branch flowing at shallower depth along the opposite flank. The hydrographic properties of the rift-valley water, and in particular the along-valley density gradient that results from a combination of the topographic isolation, the deep flow and the related mixing, are quantified. We also show that the deep currents exhibit significant variability and can be locally intense, with typical values greater than 10 cm/s. Finally, insights on the dynamical forcings of the deep currents and their variability are provided using numerical simulations, showing that tidal forcing of the mean circulation is important and that the overlying mesoscale turbulence triggers most of the variability.