Oceanic residual depth varies on 5,000 km wavelengths with amplitudes of ±1 km. A component of this short‐wavelength signal is dynamic topography caused by convective flow in the upper ∼300 km of the mantle. It exerts a significant influence on landscape evolution and sea level change, but its contribution is often excluded in geodynamic models of whole‐mantle flow. Using seismic tomography to resolve buoyancy anomalies in the oceanic upper mantle is complicated by the dominant influence of lithospheric cooling on velocity structure. Here, we remove this cooling signal from global surface wave tomographic models, revealing a correlation between positive residual depth and slow residual velocity anomalies at depths <300 km. To investigate whether these anomalies are of sufficient amplitude to account for short‐wavelength residual depth variations, we calibrate an experimentally derived parameterization of anelastic deformation at seismic frequencies to convert shear wave velocity into temperature, density, and diffusion creep viscosity. Asthenospheric temperature anomalies reach +150°C in the vicinity of major magmatic hot spots and correlate with geochemical and geophysical proxies for potential temperature along mid‐ocean ridges. Locally, we find evidence for a ∼150 km‐thick, low‐viscosity asthenospheric channel. Incorporating our revised density structure into models of whole‐mantle flow yields reasonable agreement with residual depth observations and suggests that ±30 km deviations in local lithospheric thickness account for a quarter of total amplitudes. These predictions remain compatible with geoid constraints and substantially improve the fit between power spectra of observed and predicted dynamic topography. This improvement should enable more accurate reconstruction of the spatiotemporal evolution of Cenozoic dynamic topography.

中文翻译：

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使用弹性标定参数化量化短波动态地形与上地幔热力学结构之间的关系

海洋残余深度在5,000 km波长上变化，幅度为± 1 km。该短波信号的一个组成部分是由上部〜对流流动引起的动态形貌。地幔300公里。它对景观演化和海平面变化具有重大影响，但在整个地幔流动的地球动力学模型中往往没有考虑到它的贡献。岩石圈冷却对速度结构的主要影响使利用地震层析成像解决海洋上地幔的浮力异常变得复杂。在这里，我们从整体表面波层析成像模型中删除了该冷却信号，揭示了正残留深度与深度小于300 km的慢残留速度异常之间的相关性。为了研究这些异常的振幅是否足以弥补短波残余深度的变化，我们校准了实验推导的地震频率下非弹性变形的参数化方法，以将剪切波速度转换为温度，密度，和扩散蠕变粘度。主要岩浆热点附近的软流圈温度异常达到+ 150°C，并且与大洋中脊潜在温度的地球化学和地球物理指标相关。在本地，我们发现了〜 150公里厚，低粘度的软流圈通道。将我们修改后的密度结构整合到全幔流模型中，可以与残余深度观测值合理地吻合，并表明局部岩石圈厚度的± 30 km偏差占总振幅的四分之一。这些预测与大地水准面约束保持兼容，并大大改善了观测到的动态地形的功率谱之间的拟合度。这项改进应能够更准确地重建新生代动态地形的时空演化。