Determination of the Earth's structure in Fennoscandia from GRACE and implications for the optimal post-processing of GRACE data
Determination of the Earth's structure in Fennoscandia from GRACE and implications for the optimal post-processing of GRACE data
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DOI：
10.1111/j.1365-246x.2010.04718.x
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发表时间：
2010-09
影响因子：
2.8
通讯作者：
H. Steffen;P. Wu;Hansheng Wang
中科院分区：
文献类型：
--
作者：
H. Steffen;P. Wu;Hansheng Wang
对重力恢复和气候实验（GRACE）卫星使命的数据进行分析，使我们能够确定长期质量变化的地区，如北美和芬诺斯坎迪亚的冰川均衡调整（GIA）地区。由于已有7年多的资料，所确定的趋势对于推断地幔的粘度结构是足够稳健的。在这项研究中，我们专注于芬诺斯堪的纳维亚反弹区，因为有丰富的高质量的地面数据作为地面实况。第一步，利用GRACE数据确定最佳径向（1-D）粘度剖面和岩石圈厚度组合，这是三维地球模拟中所需的背景参数。结果表明，芬诺斯坎迪亚岩石圈厚度在90 ~ 160 km之间，上地幔粘度约为[2-4] × 1020 Pa·s。然而，下地幔粘度的分辨率很差。在第二步中，GRACE数据被用来约束的3-D粘度使用球形有限元建模。在这种情况下，结果也同意与过去的调查，但GRACE数据本身不能区分横向不均匀性的地幔是热的起源，由于化学成分的变化。更值得注意的是，我们详细处理GRACE相关的问题，如实施适当的2级过滤技术和识别水文质量变化信号的最佳减少方法。事实证明，高斯滤波器技术是最适合这种类型的调查。即使是GRACE调查中使用的最好的全球水文模型仍然无法改善不匹配，因此，人们应该小心，不要盲目地使用它们来“改善”北美或其他反弹中心的GIA模型。总之，我们的研究清楚地表明，GRACE数据大大补充了GIA的研究。随着GRACE新版本的发布，以及新一代冰史模型的出现，GRACE可能会在未来几年内提高我们对地球结构和流变学的认识。
SUMMARY Analysis of data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission allows us to identify regions of long-term mass changes such as the areas of Glacial Isostatic Adjustment (GIA) in North America and Fennoscandia. As there are now more than 7 yr of data available, the determined trends are robust enough for the inference of viscosity structure of the Earth’s mantle. In this study, we focus on the Fennoscandian rebound area as there are abundant high-quality terrestrial data to use as ground-truth. In the first step, GRACE data are taken to fix the optimal radial (1-D) viscosity profile and the lithospheric thickness combination, which are needed as background parameters in 3-D earth modelling. The results are in basic agreement with results based upon relative sea level and GPS data, showing a lithospheric thickness in Fennoscandia between 90 and 160 km and an upper mantle viscosity of about [2–4] × 10 20 Pa s. The lower mantle viscosity is poorly resolved, however. In the second step, GRACE data are used to constrain the 3-D viscosity using spherical finite element modelling. In this case, the results also agree with past investigations, but GRACE data alone cannot discriminate between lateral heterogeneities in the mantle that are thermal in origin from those due to changes in chemical composition. More notably, we treat in detail GRACE-related questions such as implementation of an adequate Level-2 filter technique and identification of the best reduction method for hydrological mass change signals. It turns out that the Gaussian filter technique is the best for this type of investigation. Even the best global hydrology models used in GRACE investigations still fail to improve the mismatches—thus one should be careful not to blindly use them for ‘improving’ GIA models in North America or other centres of rebound. In conclusion, our study clearly shows that GRACE data greatly complement the study of GIA. As there are new GRACE releases in progress, and also in light of a new generation of ice history models, GRACE is likely to sharpen our insights concerning earth structure and rheology within the next few years.