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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The dynamics of mid-ocean ridge hydrothermal systems: Splitting plumes and fluctuating vent temperatures
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The dynamics of mid-ocean ridge hydrothermal systems: Splitting plumes and fluctuating vent temperatures

机译：中洋海脊热液系统的动力学：羽流分裂和排放温度波动

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We present new, accurate numerical simulations of 2D models resembling hydrothermal systems active in the high-permeability axial plane of mid-ocean ridges and show that fluid flow patterns are much more irregular and convection much more unstable than reported in previous simulation studies. First, we observe the splitting of hot, rising plumes. This phenomenon is caused by the viscous instability at the interface between hot, low-viscosity fluid and cold, high-viscosity fluid. This process, known as Taylor-Saffman fingering could potentially explain the sudden extinguishing of black smokers. Second, our simulations show that for relatively moderate permeabilities, convection is unsteady resulting in transiently varying vent temperatures. The amplitude of these fluctuations typically is 40 degrees C with a period of decades or less, depending on the permeability. Although externally imposed events such as dike injections are possible mechanisms, they are not required to explain temperature variations observed in natural systems. Our results also offer a simple explanation of how seismic events cause fluctuating temperatures: Earthquake-induced permeability-increase shifts the hydrothermal system to the unsteady regime with accompanying fluctuating vent temperatures. We demonstrate that realistic modelling of these high-Rayleigh number convection systems does not only require the use of real fluid properties, but also the use of higher order numerical methods capable of handling high-resolution meshes. Less accurate numerical solutions smear out sharp advection fronts and thereby artificially stabilize the system. (c) 2006 Elsevier B.V. All rights reserved.
机译：我们提供了类似于在中海脊高渗透性轴向平面中活跃的热液系统的二维模型的新的，精确的数值模拟，并且比以前的模拟研究报道的，流体流动模式更不规则且对流更加不稳定。首先，我们观察到炽热上升的羽流分裂。此现象是由热的低粘度流体与冷的高粘度流体之间的界面处的粘性不稳定性引起的。这个过程被称为泰勒-萨夫曼指法（Taylor-Saffman fingering），有可能解释了黑人烟民的突然熄灭。其次，我们的模拟表明，对于相对中等的渗透率，对流不稳定，会导致排气温度瞬时变化。这些波动的幅度通常为40摄氏度，持续时间不超过数十年，具体取决于磁导率。尽管外部施加的事件（例如堤坝注入）是可能的机制，但并不需要它们来解释在自然系统中观察到的温度变化。我们的结果也提供了地震事件如何引起温度波动的简单解释：地震引起的渗透率的增加将水热系统转移到不稳定的状态，伴随着排放温度的波动。我们证明，对这些高瑞利数对流系统进行逼真的建模不仅需要使用真实的流体特性，而且还需要使用能够处理高分辨率网格的高阶数值方法。精度较低的数值解会抹平尖锐的对流前沿，从而人为地使系统稳定。 （c）2006 Elsevier B.V.保留所有权利。

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