Ice age effects on the satellite-derived J ? 2 datum: Mapping the sensitivity to 3D variations in mantle viscosity
Ice age effects on the satellite-derived J ? 2 datum: Mapping the sensitivity to 3D variations in mantle viscosity
复制标题
冰河时代对卫星产生的 J 的影响？
DOI：
10.1016/j.epsl.2022.117372
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发表时间：
2022
影响因子：
5.3
通讯作者：
Kim A
中科院分区：
文献类型：
--
作者：
Kim A
基于球对称粘弹地球模型的冰川均衡调整（GIA）研究认为，地球重力位2次纬向谐波的变化率（J 2）对深层地幔的平均粘度提供了重要的约束（米特罗维察和Peltier，1993年; Nakada等人，2015; Lau等人，2016年）。为了完善这一约束，我们计算Fréchet内核使用伴随的方法，揭示了地幔粘度的三维变化的敏感性的基准。我们证明，数据的地幔敏感性很大程度上仅限于古劳伦泰德冰盖下方的区域，该冰盖覆盖了加拿大和美国东北部的大部分地区，处于末次冰期最大值（LGM）。在下地幔的下半部分，这一区域的最大灵敏度位于大的低剪切速度省（LLSVP）从地震层析成像研究的位置之外。因此，如果这些省份的低剪切速度起源于热效应，以前的推断粘度的基础上的J stec 2基准面可能高于下地幔的实际平均粘度。
Studies of glacial isostatic adjustment (GIA) based on spherically symmetric viscoelastic Earth models have argued that the rate of change of the degree 2 zonal harmonic of the Earth's geopotential, or J˙ 2, provides an important constraint on mean viscosity in the deep mantle (Mitrovica and Peltier, 1993; Nakada et al., 2015; Lau et al., 2016). To refine this constraint, we compute Fréchet kernels using an adjoint methodology that reveal the sensitivity of the datum to 3D variations in mantle viscosity. We demonstrate that the mantle sensitivity of the datum is largely limited to the region below the ancient Laurentide ice sheet that covered Canada and significant portions of the northeastern United States at Last Glacial Maximum (LGM). In the bottom half of the lower mantle, this region of maximum sensitivity lies outside the location of Large Low Shear Velocity Provinces (LLSVPs) imaged from seismic tomographic studies. Thus, if the low shear velocity of these provinces originates from thermal effects, previous inferences of viscosity based upon the J˙ 2 datum are likely higher than the actual mean viscosity of the lower mantle.