The dynamics of mid-ocean ridge hydrothermal systems:: Splitting plumes and fluctuating vent temperatures
The dynamics of mid-ocean ridge hydrothermal systems:: Splitting plumes and fluctuating vent temperatures
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DOI：
10.1016/j.epsl.2006.02.044
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发表时间：
2006-05-15
影响因子：
5.3
通讯作者：
Matthai, Stephan
中科院分区：
文献类型：
--
作者：
Coumou, Dim;Driesner, Thomas;Matthai, Stephan
我们提出了新的，准确的数值模拟的2D模型类似的热液系统活跃在高渗透率的轴向平面的洋中脊，并表明，流体流动模式更不规则，对流更不稳定，比以前的模拟研究报告。首先，我们观察到热的上升羽流的分裂。这种现象是由热的低粘度流体和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，可能解释了黑人吸烟者突然熄灭的原因。其次，我们的模拟表明，相对中等的渗透率，对流是不稳定的，导致瞬态变化的排气口温度。这些波动的幅度通常为40摄氏度，周期为几十年或更短，这取决于渗透率。虽然外部强加的事件，如堤坝注入是可能的机制，他们不需要解释在自然系统中观察到的温度变化。我们的研究结果还提供了一个简单的解释，地震事件如何引起波动的温度：地震引起的渗透率增加的热液系统转移到不稳定的制度，伴随着波动的喷口温度。我们表明，这些高瑞利数对流系统的现实建模不仅需要使用真实的流体性质，但也使用高阶数值方法能够处理高分辨率网格。不太精确的数值解模糊了尖锐的平流锋，从而人为地稳定了系统。(c)2006 Elsevier B. V.保留所有权利。
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.