What drives 20th century polar motion?
What drives 20th century polar motion?
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DOI：
10.1016/j.epsl.2018.08.059
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发表时间：
2018-11-15
影响因子：
5.3
通讯作者：
Ivins, Erik R.
中科院分区：
文献类型：
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作者：
Adhikari, Surendra;Caron, Lambert;Ivins, Erik R.
天体测量和大地测量表明，地球自转轴的平均位置在世纪以10.5 +/- 0.9厘米/年的平均速度穿过固体地壳向加拿大拉布拉多漂移。了解这种长期极地运动（SPM）的起源对于模拟全球气候具有重要意义，因为它提供了与冰质量平衡和海平面上升的联系。然而，一个令人困惑的问题是，虽然冰川均衡调整（GIA）模型令人满意地解释了SPM的方向，相关的振幅预测是不够的。我们的贝叶斯GIA分析，从相对海平面和垂直陆地运动数据的限制，揭示了这一过程只占33 +/- 18%的观测SPM振幅。这一不足促使对SPM驱动因素进行更广泛的重新评估。为了解决这个问题，我们组装了一个完整的重建地球表面的质量运输来自最近的进展，在全球世纪冰冻圈，水文，海洋和地震的质量交换建模。然而，即使考虑到每个驱动程序的误差统计数据，相加的信号也无法完全与观察到的SPM一致。我们调查了一个额外的激发源：地幔对流引起的地球惯性张量的变化。复杂的模型，最近在构造板块重建，结合大地水准面和地震层析成像模型。在这里，我们使用这些模型来计算SPM的新估计。虽然对流驱动的SPM具有相当大的不确定性，但283个最新模型的平均方向与剩余SPM一致（在2.7 +/- 14.8度内），显着减少了观测和预测之间的差距。我们断言，一个关键的机制，驱动世纪SPM是长期的质量运动，由于地幔对流。(C)2018爱思唯尔B. V.保留所有权利。
Astrometric and geodetic measurements show that the mean position of Earth's spin axis drifted through the solid crust toward Labrador, Canada at an average speed of 10.5 +/- 0.9 cm/yr during the 20th century. Understanding the origins of this secular polar motion (SPM) has significance for modeling the global climate, as it provides a link to ice mass balance and sea-level rise. A perplexing issue, however, is that while glacial isostatic adjustment (GIA) models satisfactorily explain the direction of SPM, the associated prediction of the amplitude is insufficient. Our Bayesian GIA analysis, with constraints from relative sea-level and vertical land motion data, reveals that this process only accounts for 33 +/- 18% of the observed SPM amplitude. This shortfall motivates a more broadly scoped reassessment of SPM drivers. To address this, we assemble a complete reconstruction of Earth's surface mass transport derived from recent advancements in modeling the global 20th century cryospheric, hydrologic, oceanic, and seismogenic mass exchange. The summed signals, nonetheless, cannot fully reconcile the observed SPM, even when considering the error statistics of each driver. We investigate an additional excitation source: changes in Earth's inertia tensor caused by mantle convection. Sophisticated models have recently been advanced in tectonic plate reconstructions, in conjunction with geoid and seismic tomographic models. Here we use these models to compute new estimates of SPM. While the convection-driven SPM has considerable uncertainty, the average direction of 283 recent models aligns with the residual SPM (within 2.7 +/- 14.8 degrees), significantly reducing the gap between observation and prediction. We assert that one key mechanism for driving 20th century SPM is long-term mass movement due to mantle convection. (C) 2018 Elsevier B.V. All rights reserved.