瑞士苏黎世联邦理工大学Kiani Shahvandi Mostafa团队，报道了地核、地幔和气候过程对地球极运动的贡献。相关论文于2024年7月12日发表在《自然—地球科学》杂志上。

据悉，随着时间的推移，地球的自转轴相对于地壳缓慢移动。来自天文学和更现代的大地测量长达120年的极移记录显示，年际和多年代际波动为20至40毫角秒，叠加在每年约3毫角秒的长期趋势上。地球的极移被认为是由各种表面和内部过程驱动的，但是这些过程是如何运作和相互作用来产生观测到的信号仍然是一个谜。

研究人员表示，由一组物理信息组成的神经网络所做的预测，用于捕获地球物理过程，可以解释观测到的极移的主要特征。长期趋势的主要原因是冰川均衡调整和地幔对流。地球表面的质量再分配——例如，冰融化和全球储水量的变化——产生了相对微弱的趋势，但却解释了大约90%的年际和多年代际变化。

该研究还发现，由于地核-地幔边界的转矩变化或地核响应地表质量变化的动力学反馈，地核过程对极地运动的长期趋势和波动都有贡献。该发现提供了对过去一个世纪以来观测很少的地核-地幔相互作用和全球冰质量平衡的限制，并表明了与气候相关的地表过程和地核动力学之间的反馈作用。

附：英文原文

Title: Contributions of core, mantle and climatological processes to Earth’s polar motion

Author: Kiani Shahvandi, Mostafa, Adhikari, Surendra, Dumberry, Mathieu, Modiri, Sadegh, Heinkelmann, Robert, Schuh, Harald, Mishra, Siddhartha, Soja, Benedikt

Issue&Volume: 2024-07-12

Abstract: Earth’s spin axis slowly moves relative to the crust over time. A 120-year-long record of this polar motion from astronomical and more modern geodetic measurements displays interannual and multidecadal fluctuations of 20 to 40 milliarcseconds superimposed on a secular trend of about 3 milliarcseconds per year. Earth’s polar motion is thought to be driven by various surface and interior processes, but how these processes operate and interact to produce the observed signal remains enigmatic. Here we show that predictions made by an ensemble of physics-informed neural networks trained on measurements to capture geophysical processes can explain the main features of the observed polar motion. We find that glacial isostatic adjustment and mantle convection primarily account for the secular trend. Mass redistribution on the Earth’s surface—for example, ice melting and global changes in water storage—yields a relatively weak trend but explains about 90% of the interannual and multidecadal variations. We also find that core processes contribute to both the secular trend and fluctuations in polar motion, either due to variations in torque at the core–mantle boundary or dynamical feedback of the core in response to surface mass changes. Our findings provide constraints on core–mantle interactions for which observations are rare and global ice mass balance over the past century and suggest feedback operating between climate-related surface processes and core dynamics.

DOI: 10.1038/s41561-024-01478-2

Source: https://www.nature.com/articles/s41561-024-01478-2