Changes in surface environments and Earth's interior and Earth's rotational variations

周期短于几年的快速地磁波动，即所谓的地磁急动，似乎与地球日长（LOD）和钱德勒摆动相位的变化一致。我们指出，快速加速的CMB流可以产生扭矩的CMB产生观测到的LOD衍生物与~0.1毫秒yr-1，但不产生太多的极运动。另一方面，地幔最底层D”层的粘度控制着地幔对流引起的地球自转变化和冰川均衡调整等地球动力学过程。根据钱德勒摆动的衰减和半日至18.6年的潮汐形变，结合冰后期地壳均衡调整观测资料的约束，我们认为，在300 km层底部的有效粘滞系数为1019- 1020 Pa·s，而D”层底部（100 km）的有效粘滞系数也小于1018 Pa·s。通过考虑这些结果和最近的高山冰川和极地冰盖融化事件，我们现在正在研究地幔对流的时间变化引起的地球自转变化。

Rapid geomagnetic fluctuations with periods less than a few years, so called geomagnetic jerks, seem to be coincident with changes in Earth’s length of day (LOD) and phase of the Chandler wobble. We indicated that rapid accelerations in the CMB flow can produce torques at the CMB generating observed LOD derivative with ~0.1 ms yr-1, but do not produce much for the polar motion. On the other hand, viscosity of the D” layer of the Earth’s mantle, the lowermost layer in the Earth’s mantle, controls a number of geodynamic processes such as the Earth’s rotational variations due to mantle convection and glacial isostatic adjustment. We showed that the decay of Chandler wobble and semi-diurnal to 18.6 years tidal deformation combined with the constraints from the postglacial isostatic adjustment observations suggest that the effective viscosity in the bottom ~300 km layer is 1019-1020Pa s, and also the effective viscosity of the bottom part of the D” layer (~100 km thickness) is less than 1018Pa s. By considering these results and recent melting events of mountain glaciers and polar ice sheets, we are now studying the Earth’s rotational variations caused by the temporal changes in mantle convection.