Regional stratification at the top of Earth's core due to core-mantle boundary heat flux variations
Regional stratification at the top of Earth's core due to core-mantle boundary heat flux variations
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DOI：
10.1038/s41561-019-0381-z
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发表时间：
2019-07-01
影响因子：
18.3
通讯作者：
Aurnou, Jon
中科院分区：
文献类型：
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作者：
Mound, Jon;Davies, Chris;Aurnou, Jon
地球的磁场是由其流体外核的湍流运动产生的。虽然外核的大部分是强烈的对流和良好的混合，一些地震，地磁和地球动力学的证据表明，一个全球稳定分层层存在于地球核心的顶部。这样的一个层将强烈影响热，化学和动量交换的核-幔边界，从而有重要的影响，动力学和演化的核心。在这里，我们认为，相关的情况是不是全球分层，而是区域分层所产生的热通量的横向变化在核幔边界。使用我们广泛的数值模拟套件的流体核心的动力学与异质核幔边界热通量，我们预测，热区域逆温层延伸数百公里的核心下的最低地幔的异常热的地区。虽然大多数最外层的核心仍然积极对流，足够大和强大的区域逆温层产生一维的温度分布，模仿全球分层层以下的核-幔边界-一个明显的热分层，尽管平均热通量的核-幔边界是强烈的超绝热。
Earth's magnetic field is generated by turbulent motion in its fluid outer core. Although the bulk of the outer core is vigorously convecting and well mixed, some seismic, geomagnetic and geodynamic evidence suggests that a global stably stratified layer exists at the top of Earth's core. Such a layer would strongly influence thermal, chemical and momentum exchange across the core-mantle boundary and thus have important implications for the dynamics and evolution of the core. Here we argue that the relevant scenario is not global stratification, but rather regional stratification arising solely from the lateral variations in heat flux at the core-mantle boundary. Using our extensive suite of numerical simulations of the dynamics of the fluid core with heterogeneous core-mantle boundary heat flux, we predict that thermal regional inversion layers extend hundreds of kilometres into the core under anomalously hot regions of the lowermost mantle. Although the majority of the outermost core remains actively convecting, sufficiently large and strong regional inversion layers produce a one-dimensional temperature profile that mimics a globally stratified layer below the core-mantle boundary-an apparent thermal stratification despite the average heat flux across the core-mantle boundary being strongly superadiabatic.