Polar wander of the Earth associated with the Quaternary glacial cycle on a convecting mantle
Polar wander of the Earth associated with the Quaternary glacial cycle on a convecting mantle
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DOI：
10.1111/j.1365-246x.2009.04289.x
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发表时间：
2009-10
影响因子：
2.8
通讯作者：
M. Nakada
中科院分区：
文献类型：
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作者：
M. Nakada
摘要根据第四纪冰期旋回的冰川均衡调整（GIA），对现今观测到的向哈德逊湾移动速度为100万年-100万年的真极移（TPW）进行了全面的检验。然而，这一观测受到现今极地冰盖和高山冰川融化事件以及地幔对流过程的影响。在这项研究中，我检查TPW由于GIA和对流过程的发展刘维方程，包括这两个过程，简称为广义刘维方程在这里。推广的刘维方程使得计算与对流有关的非强迫惯性要素的影响成为可能（I11，I22，I33和I12）和强迫要素（I13和I23）在第四纪冰期阶段的极移，并清楚地表明，地球的过度扁平，从非流体静力大地水准面推断，如Mitrovica等人（2005）所讨论的，稳定了极移。此外，检验随时间变化的对流过程对TPW影响的数值试验表明，惯性张量随时间变化的合理对流情景为1031 kg m2 Myr−1（Ricard等人，1993）对目前观测到的TPW贡献不大;此外，当对流强迫率dI 13/dt和dI 23/dt大于10.5 × 1031 kg m2 Myr−1时，预测的TPW与观测值有显著差异。这些结果可能为分离GIA和对流对当今观测到的极移的贡献提供了一个框架。
SUMMARY Observed true polar wander (TPW) at the present-day, with the speed of ∼1° Myr−1 towards Hudson Bay, has been generally examined based on the glacial isostatic adjustment (GIA) for the Quaternary glacial cycle. The observation is, however, affected by the present-day melting events of polar ice sheets and mountain glaciers and convective processes in the mantle. In this study, I examine TPW due to GIA and convective processes by developing the Liouville equation including these two processes, referred to as generalized Liouville equation here. The generalized Liouville equation makes it possible to evaluate the effects of convective related non-forcing inertia elements (I11, I22, I33 and I12) and forcing elements (I13 and I23) on the polar wander for the Quaternary ice age phase, and clearly indicates that the excess flattening of the Earth, inferred from the non-hydrostatic geoid, stabilizes the polar motion as discussed by Mitrovica et al. (2005). Also, numerical experiments for examining the effects of time-dependent convective processes on TPW indicate that reasonable convection scenarios with a time dependence in the inertia tensor of ∼1031 kg m2 Myr−1 (Ricard et al. 1993) insignificantly contribute to the observed present-day TPW; moreover, the predicted TPW with magnitude of convective related forcing rates, dI13/dt and dI23/dt, larger than ∼5 × 1031 kg m2 Myr−1 is significantly different from the observation. These results may provide a framework for separating the contributions of GIA and convection to the observed present-day polar wander.