A numerical simulation of the evolution of temperature and CO2 stratification in Lake Nyos since the 1986 disaster
A numerical simulation of the evolution of temperature and CO2 stratification in Lake Nyos since the 1986 disaster
复制标题
自 1986 年灾难以来尼奥斯湖温度和二氧化碳分层演变的数值模拟
DOI：
10.1029/96jb00324
复制
发表时间：
1996
影响因子：
--
通讯作者：
S. J. Freeth
中科院分区：
文献类型：
--
作者：
L. Kantha;S. J. Freeth
一维数值模型已被用来模拟自 1986 年灾难以来尼奥斯湖温度和二氧化碳分层的演变。它采用了二阶矩湍流闭合方案，用于在湖的上层进行混合、加热和冷却。考虑了流入的溪流水以及湖底二氧化碳、热量和溶解固体的输入的影响。该模型根据 1986 年灾难性排气事件后立即观察到的条件进行初始化，并在季节性调节的昼间加热和夜间冷却以及地表夏季大量降水的推动下向前积分 10 年。研究了四种可能的情况。第一个模拟考虑了正常的季节性加热/冷却循环以及底部热量、溶解固体和二氧化碳的稳定输入。它表明，在正常的季节性强迫下，该湖的上层相当稳定，但底层在不到十年的时间内达到了很高的二氧化碳浓度。第二个模拟考虑在湖底引入较冷的水域，这些水域含有较少的二氧化碳，会暂时破坏底层的稳定。第三次和第四次模拟考虑了异常表面强迫条件，这些条件可能会在冷却季节产生异常混合层加深，从而释放出储存在正常混合层正下方的二氧化碳。这些结果表明，底层的不稳定更有可能导致大规模和灾难性的脱气。结果还证明了数值模型在尼奥斯湖等火山口/火山口湖研究中的实用性。
A one-dimensional numerical model has been applied to simulate the evolution of the temperature and CO2 stratification in Lake Nyos since the 1986 disaster. It incorporates a second-moment turbulence closure scheme for mixing and heating and cooling in the upper layers of the lake. The effects of inflowing stream water and input of the CO2, heat, and dissolved solids at the bottom of the lake are taken into account. The model is initialized by conditions observed immediately after the disastrous outgassing event in 1986 and integrated forward for 10 years, forced by seasonally modulated diurnal heating and nocturnal cooling and heavy summer time precipitation at the surface. Four possible conditions are investigated. The first simulation considers the normal seasonal heating/cooling cycle and steady input of heat, dissolved solids, and CO2 at the bottom. It shows that the upper layers of the lake are quite stable under normal seasonal forcing but the bottom layers reach high CO2 concentrations in less than a decade. The second simulation considers a brief introduction at the bottom of the lake of cooler waters that contain less CO2 and temporarily destabilize the bottom layers. The third and fourth simulations consider anomalous surface forcing conditions that can produce anomalous mixed layer deepening during the cooling seasons, capable of releasing the CO2 stored immediately below the normal mixed layer. These results suggest that a destabilization of the bottom layers is more likely to lead to massive and catastrophic degassing. The results also demonstrate the utility of a numerical model in investigations of caldera/crater lakes such as Lake Nyos.