Feasibility study to identify deep Earth signals in current and future gravity field missions

下一代重力任务预计将大大提高地球重力模型的精度。周期性信号和趋势与地球系统中的质量再分布有关，并携带关于大气层、冰冻圈、大陆水圈、海洋和固体地球中动态过程的基本信息。人们普遍认为，来自固体地球深部的重力信号低于卫星重力飞行任务的探测极限，因为人们认为这些信号的幅度非常小，并限于最长的空间和时间尺度。然而，从地质记录中得到的有力证据表明，在区域尺度上，特别是在沿着被动大陆边，存在着非常快速的隆起和沉降事件。根据区域地震地层学、景观演化研究和河流剖面分析，这些隆升和沉降事件是下伏地幔流动的结果。在这里，我们建议利用高分辨率的全球地幔对流模型能够解决细尺度地幔流结合创新的伴随方法。伴随方法使我们能够获得全球地幔流的时间轨迹，从而提供一阶估计的时间变化的重力信号有关的固体地球。

Next generation gravity missions are expected to improve the accuracy of temporal Earth gravity models significantly. Periodic signals and trends are related to mass redistributions in the Earth system and carry essential information on dynamic processes in the atmosphere, cryosphere, continental hydrosphere, the oceans and the solid Earth. Gravity signals from the deep solid Earth are commonly thought to lie below the detection limit of satellite gravity missions, as one assumes them to have very small amplitudes and be restricted to the longest spatial and temporal scales. However, robust evidence from geologic records exists for episodes of very rapid uplift and subsidence events at regional scales, especially along passive continental margins. These uplift and subsidence events, which are inferred from regional seismic stratigraphy, landscape evolution studies, and the analysis of river profiles, result from flow in the underlying mantle. Here we propose to exploit high resolution global mantle convection models capable of resolving fine scale mantle flow in conjunction with an innovative adjoint method. The adjoint method allows us to derive time trajectories for global mantle flow, thus providing first order estimates for temporal variations of gravity signals related to solid Earth.