Reevaluation of the viscoelastic and elastic responses to the past and present-day ice changes in Southeast Alaska
Reevaluation of the viscoelastic and elastic responses to the past and present-day ice changes in Southeast Alaska
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DOI：
10.1016/j.tecto.2010.05.009
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发表时间：
2011-11
期刊：
影响因子：
2.9
通讯作者：
Tadahiro Sato;C. Larsen;S. Miura;Y. Ohta;H. Fujimoto;Wenke Sun;R. Motyka;J. Freymueller
中科院分区：
文献类型：
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作者：
Tadahiro Sato;C. Larsen;S. Miura;Y. Ohta;H. Fujimoto;Wenke Sun;R. Motyka;J. Freymueller
我们已经重新评估了粘弹性和弹性响应的过去和现在的冰变化在阿拉斯加东南部（SE-AK）的GPS数据集的基础上，结合2005年以前发表的数据与最近编制的额外的隆起率。有22个新的全球定位系统站点，总共有91个站点。数据集的平均观测时期为2003年中期。在这里，我们考虑了三个冰卸载的影响，由于末次盛冰期（LGM），小冰期（LIA）和现在的冰融化（PDIM）。我们还研究了估计的岩石圈厚度和软流圈粘度的依赖PDIM模型。在这个测试中，使用了两个PDIM模型：一个是一个模型，这里称为UAF 05冰模型，其平均时期是20世纪70年代中期，另一个是一个模型，这里称为UAF 07模型，其平均时期是20世纪80年代中期。对观测值和模型预测值之间的失配进行统计检验表明，基于最小χ 2的大小和残差分布与高斯函数的一致性，UAF 07给出的结果比UAF 05一致得多。我们测试了两种不同的地幔粘度结构：一种是类似于2005年发表的论文所用模型的两层模型，另一种是四层模型。对于两层模式，在95%置信水平下，岩石圈厚度和软流圈粘度（厚度为110 km）的最佳值分别为54（45-65）km和5.58（4.0-12.0）（单位为1018 Pas）。另一方面，对于4层模型，以1018 Pas为单位，最佳值分别为60（42-63）km和10.0（3.0-13）。GPS数据分析结果与模型计算结果的比较表明，观测不仅检测到SE-AK的隆升速率，但也被认为是由于20世纪90年代后的冰川变化的时间变化。
We have reevaluated the viscoelastic and elastic responses to the past and present-day ice changes in Southeast Alaska (SE-AK) based on a GPS data set by combining the data previously published in 2005 with additional uplift rates compiled recently. There are 22 new GPS sites, yielding a total of 91 sites. The mean observation epoch of the data sets is the middle of 2003. Here we considered three ice unloading effects due to the last glacial maximum (LGM), the Little Ice Age (LIA) and the present-day ice melting (PDIM). We also examined the dependency of the estimated lithospheric thickness and the asthenospheric viscosity on PDIM models. For this test, two PDIM models were used: one is a model, called here the UAF05 ice model, whose mean epoch is the mid-1970s, and the other is a model, called here the UAF07 model, whose mean epoch is the mid-1980s. Statistical examinations of the misfits between observations and model predictions indicate that UAF07 gives much more consistent results than UAF05, based on the magnitude of the minimum χ2and the agreement of the residual distribution with a Gaussian function. We have tested two different kinds of mantle viscosity structure: a 2-layer model similar to the model used the paper previously published in 2005 and a 4-layer model. For the 2-layer model, at the 95% confidence level, the optimum values for the lithospheric thickness and the asthenospheric viscosity (with a thickness of 110km) are 54 (45–65) km and 5.58 (4.0–12.0) in unit of 1018Pas, respectively. On the other hand, for the 4-layer model, the best values were 60 (42–63) km and 10.0 (3.0–13) in unit of 1018Pas, respectively. The comparison between the analysis results for GPS data and the model computations indicates that the observations detect not only the uplift rates in SE-AK but also their time variations which are considered to be due to the glacier changes after the 1990s.