Earth's multi-scale topographic response to global mantle flow
Earth's multi-scale topographic response to global mantle flow
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DOI：
10.1038/s41561-019-0441-4
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发表时间：
2019-10-01
影响因子：
18.3
通讯作者：
Wilsons, C. R.
中科院分区：
文献类型：
--
作者：
Davies, D. R.;Valentine, A. P.;Wilsons, C. R.
地球表面的地形是地球动态的直接物理表达。大多数是均衡的，受地壳和岩石圈内的厚度和密度变化控制，但相当大一部分来自下伏地幔对流施加的力。这种动态地形直接将地表环境的演化与地球深层联系起来，但地幔流动模拟的预测往往与地质记录的推断不一致，对其空间模式、波长和幅度几乎没有共识。在这里，我们证明了以前预测模型和观测约束之间的比较受到主观选择的影响。使用海洋下剩余地形的测量，以及执行球面调和分析的分层贝叶斯方法，我们生成了对地球海洋剩余地形功率谱的稳健估计。这表明水负载功率为0.5+/-0.35公里(2)，在长波长(类似于10(4)公里)时峰值幅度高达类似于0.8+/-0.1公里(类似于10(4)公里)，在较短波长(类似于10(3)公里)时减小约一个数量级。我们表明，只有在考虑岩石圈结构及其对地幔流动的影响时，地球动力学模拟才能与观测约束相一致。这表明深部(长波)和浅部(短波)过程都是至关重要的，并意味着动态地形与地球岩石圈的结构和演化密切相关。
Earth's surface topography is a direct physical expression of our planet's dynamics. Most is isostatic, controlled by thickness and density variations within the crust and lithosphere, but a substantial proportion arises from forces exerted by underlying mantle convection. This dynamic topography directly connects the evolution of surface environments to Earth's deep interior, but predictions from mantle flow simulations are often inconsistent with inferences from the geological record, with little consensus about its spatial pattern, wavelength and amplitude. Here, we demonstrate that previous comparisons between predictive models and observational constraints have been biased by subjective choices. Using measurements of residual topography beneath the oceans, and a hierarchical Bayesian approach to performing spherical harmonic analyses, we generate a robust estimate of Earth's oceanic residual topography power spectrum. This indicates water-loaded power of 0.5 +/- 0.35 km(2) and peak amplitudes of up to similar to 0.8 +/- 0.1km at long wavelengths (similar to 10(4) km), decreasing by roughly one order of magnitude at shorter wavelengths (similar to 10(3) km). We show that geodynamical simulations can be reconciled with observational constraints only if they incorporate lithospheric structure and its impact on mantle flow. This demonstrates that both deep (long-wavelength) and shallow (shorter-wavelength) processes are crucial, and implies that dynamic topography is intimately connected to the structure and evolution of Earth's lithosphere.