Weak mixing in Lake Kivu: New insights indicate increasing risk of uncontrolled gas eruption
Weak mixing in Lake Kivu: New insights indicate increasing risk of uncontrolled gas eruption
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基伍湖的弱混合：新的见解表明不受控制的气体喷发的风险正在增加
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
A. Wüest
中科院分区：
文献类型：
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作者：
M. Schmid;M. Halbwachs;B. Wehrli;A. Wüest
东非裂谷基伍湖的深水中含有大量溶解的二氧化碳和甲烷。湖中岩浆喷发可能引发这些气体的一小部分释放，这将对居住在湖边的200万人造成灾难性的后果。迄今为止，湖泊的安全评价是基于深水气体浓度处于稳定状态，停留时间为400年的假设。紊流输运被认为是垂直交换的主要途径。最近对湖泊垂直输送过程的测量和分析从根本上改变了这种评价。垂直湍流交换是可以忽略不计的，这是由数百个双扩散层组成的壮观集合所证明的。气体主要通过缓慢的上升流输送出深部带，停留时间为800-1000年。我们的研究结果表明，沉积物中的甲烷产量最近有所增加，导致深水中的气体积聚，从而减少了触发破坏性气体释放所需的热量输入。按照目前估计的CH4产量，气体浓度可能在本世纪内接近饱和。
The deep waters of the East African Rift Lake Kivu contain large amounts of dissolved carbon dioxide and methane. The release of a fraction of these gases, which could be triggered by a magma eruption within the lake, would have catastrophic consequences for the two million people living on its shore. Up to now the safety assessment of the lake was based on the assumption that the gas concentrations in the deep waters are in a steady state with a residence time of 400 years. Turbulent transport was regarded as the main pathway of vertical exchange. Recent measurements and the analysis of the vertical transport processes in the lake radically change this evaluation. The vertical turbulent exchange is negligible, as documented by a spectacular set of several hundred double‐diffusive layers. Gases are mainly transported out of the deep zones by a slow upwelling with a residence time of 800–1000 years. Our results indicate that the methane production within the sediment has recently increased, leading to a gas accumulation in the deep waters and consequently decreasing the heat input needed to trigger a devastating gas release. With the estimated current CH4 production, the gas concentrations could approach saturation within this century.