Abstract

Observation of the variations in the Earth’s rotation at time scales ranging from subdiurnal to multidecadal allows us to learn about its deep interior structure. We review all three types of motion of the Earth’s rotation axis: polar motion (PM), length of day variations ( \(\Delta \text {LOD}\) ) and nutations, with particular attention to how the combination of geodetic, magnetic and gravity observations provides insight into the dynamics of the liquid core, including its interactions with the mantle. Models of the Earth’s PM are able to explain most of the observed signal with the exception of the so-called Markowitz wobble. In addition, whereas the quasi-six year oscillations (SYO) observed in both \(\Delta \text {LOD}\) and PM can be explained as the result of Atmosphere, Oceans and Hydrosphere Forcing (AOH) for PM, this is not true for \(\Delta \text {LOD}\) where the subtraction of the AOH only makes the signal more visible. This points to a missing—possibly common—interpretation related to deep interior dynamics, the latter being also the most likely explanation of other oscillations in \(\Delta \text {LOD}\) on interannual timescales. Deep Earth’s structure and dynamics also have an impact on the nutations reflected in the values of the Basic Earth Parameters (BEP). We give a brief review of recent works aiming to independently evaluate the BEP and their implications for the study of deep interior dynamics.

中文翻译：

---

地球自转：观测和与深层内部的关系

摘要

观察地球自转在从昼夜到几十年的时间尺度上的变化，使我们能够了解其深层内部结构。我们回顾了地球自转轴的所有三种运动类型：极地运动 (PM)、日长变化 ( \(\Delta \text {LOD}\) ) 和章动，特别注意大地测量、磁力的组合如何重力观测提供了对液核动力学的深入了解，包括它与地幔的相互作用。除了所谓的马科维茨摆动之外，地球 PM 模型能够解释大部分观测到的信号。此外，虽然在\(\Delta \text {LOD}\) 和 PM 可以解释为 PM 的大气、海洋和水圈强迫 (AOH) 的结果，这对于\(\Delta \text {LOD}\) 而言并非如此，其中 AOH 的减法只会使信号更加明显。这指出了与深层内部动力学相关的缺失（可能是常见的）解释，后者也是年际时间尺度上\(\Delta \text {LOD}\)中其他振荡的最可能解释。深部地球的结构和动力学也对反映在基本地球参数 (BEP) 值中的章动产生影响。我们简要回顾了近期旨在独立评估 BEP 及其对深层内部动力学研究的影响的工作。