Scaling laws for convection with temperature-dependent viscosity and grain-damage
Scaling laws for convection with temperature-dependent viscosity and grain-damage
复制标题
具有与温度相关的粘度和颗粒损伤的对流的缩放定律
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
D. Bercovici
中科院分区：
文献类型：
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作者：
B. Foley;D. Bercovici
具有颗粒损伤的对流数值实验被用来开发对流热流、地幔速度和跨越停滞盖和板块构造区域的板块速度的标度定律。按照复杂性逐渐增加的顺序提出了三种主要情况：一种简单情况，其中粘度仅取决于晶粒尺寸；一种情况，其中粘度取决于温度和晶粒尺寸；最后一种情况，其中粘度对温度和晶粒尺寸敏感，并且晶粒生长（或愈合）也对温度敏感。在所有情况下，由于颗粒损坏的影响，颗粒损坏对流的规模与牛顿对流不同。对于完全真实的情况，数值结果显示停滞的盖对流、类似于与温度无关的粘度情况的完全动员的对流，以及部分流动或过渡的对流，具体取决于愈合率的损伤、瑞利数以及粘度和愈合的活化能。将我们的比例定律应用于地球和金星完全现实的情况，我们证明，表面温度的升高会显着降低板块速度和热流，从根本上关闭板块构造，这是由于岩石圈剪切带愈合的增加，如之前所提出的。与许多以前的研究相反，停滞盖和完全流动状态之间的过渡状态很大，并且从停滞盖到移动对流的过渡是渐进和连续的。因此，行星可以表现出全方位的表面移动性，这与通常假设的完全移动的盖行星和静止的盖行星的双峰分布相反。
Numerical experiments of convection with grain-damage are used to develop scaling laws for convective heat flow, mantle velocity, and plate velocity across the stagnant lid and plate-tectonic regimes. Three main cases are presented in order of increasing complexity: a simple case wherein viscosity is only dependent on grainsize, a case where viscosity depends on temperature and grainsize, and finally a case where viscosity is temperature and grainsize sensitive, and the grain-growth (or healing) is also temperature sensitive. In all cases, convection with grain-damage scales differently than Newtonian convection due to the effects of grain-damage. For the fully realistic case, numerical results show stagnant lid convection, fully mobilized convection that resembles the temperature-independent viscosity case, and partially mobile or transitional convection, depending on damage to healing ratio, Rayleigh number, and the activation energies for viscosity and healing. Applying our scaling laws for the fully realistic case to Earth and Venus we demonstrate that increasing surface temperature dramatically decreases plate speed and heat flow, essentially shutting down plate tectonics, due to increased healing in lithospheric shear zones, as proposed previously. Contrary to many previous studies, the transitional regime between the stagnant lid and fully mobilized regimes is large, and the transition from stagnant lid to mobile convection is gradual and continuous. Thus planets could exhibit a full range of surface mobility, as opposed to the bimodal distribution of fully mobile lid planets and stagnant lid planets that is typically assumed.