Mantle convection with longest‐wavelength thermal heterogeneity in a 3‐D spherical model: Degree one or two?
Mantle convection with longest‐wavelength thermal heterogeneity in a 3‐D spherical model: Degree one or two?
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DOI：
10.1029/2008gl036059
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发表时间：
2008-12
影响因子：
5.2
通讯作者：
Masaki Yoshida
中科院分区：
文献类型：
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作者：
Masaki Yoshida
用三维球面模式研究了迟滞盖区最长波长地幔对流的形成。底部的瑞利数固定为107。考虑到温度相关的流变性，无论是纯基础加热还是混合(即基础和内部)加热模式，都会发生一级主导热对流。对于纯基本加热模式，在Boussinesq和Extended-Boussinesq流体中，当随温度变化的粘度差为103-104时，发生一级对流。然而，对于扩展的Boussinesq流体，一级对流可能只在基本加热模式下发生：在混合加热模式下，一级对流转变为高度模式对流，这可能是由于上/下流羽流上方的高粘性盖子内的粘性耗散增强所致。在本研究中没有观察到具有片状下沉的二级对流的地球物理关联性。地幔顶部的粘塑性流变性包裹体破坏了一级对流。
The formation of longest‐wavelength mantle convection in the sluggish‐lid regime is investigated using a three‐dimensional spherical model. The bottom Rayleigh number is fixed at 107. Considering temperature‐dependent rheology, degree‐one dominant thermal convection occurs for both purely basal heating and mixed (i.e., basal and internal) heating modes. For the purely basal heating mode, degree‐one convection occurs when the viscosity contrast due to temperature‐dependent rheology is 103–104 in both Boussinesq and extended‐Boussinesq fluids. However, with extended‐Boussinesq fluid, degree‐one convection may only occur in the basal heating mode: In the mixed heating mode, degree‐one convection shifts to one with high‐degree modes, presumably because of enhanced viscous dissipation in the highly viscous lid over up/downwelling plumes. The geophysically relevant degree‐two convection with sheet‐like downwellings is not observed in this study. The inclusion of visco‐plastic rheology in the top part of the mantle breaks down degree‐one convection.