Forte Alessandro M, Mitrovica Jerry X, Espesset Aude
Department of Earth Sciences, University of Western Ontario, London, Canada.
Philos Trans A Math Phys Eng Sci. 2002 Nov 15;360(1800):2521-43. doi: 10.1098/rsta.2002.1079.
We revisit a recent study by Forte & Mitrovica in which global geophysical observables associated with mantle convection were inverted and the existence of a strong increase in viscosity near a depth of 2000 km was inferred. Employing mineral-physics data and theory we also showed that, although there are chemical anomalies in the lowermost mantle, they are unable to inhibit the dominant thermal buoyancy of the deep-mantle mega-plumes below Africa and the Pacific Ocean. New Monte Carlo simulations are employed to explore the impact of uncertainties in current mineral-physics constraints on inferences of deep-mantle thermochemical structure. To explore the impact of the high-viscosity peak at a depth of 2000 km on the evolution of lower-mantle structure, we carried out time-dependent convection simulations. The latter show that the stability and longevity of the dominant long-wavelength heterogeneity in the lowermost mantle are controlled by this viscosity peak.
我们重新审视了福特和米特罗维察最近的一项研究，该研究对与地幔对流相关的全球地球物理观测数据进行了反演，并推断出在深度约2000公里处粘度有显著增加。利用矿物物理数据和理论，我们还表明，尽管下地幔存在化学异常，但它们无法抑制非洲和太平洋下方深部地幔巨型地幔柱的主要热浮力。我们采用新的蒙特卡罗模拟来探究当前矿物物理约束中的不确定性对深部地幔热化学结构推断的影响。为了探究2000公里深度处的高粘度峰值对下地幔结构演化的影响，我们进行了时间相关的对流模拟。后者表明，下地幔中占主导地位的长波长不均匀性的稳定性和寿命受此粘度峰值控制。
