Glacial isostatic adjustment (GIA) describes the response of the solid Earth, oceans, and gravitational field to the spatio-temporal evolution of ice sheets during a glacial cycle. Present-day vertical displacements and sea-level changes vary throughout eastern North America in response to the melting of the Laurentide Ice Sheet following the Last Glacial Maximum. We use the open-source software SELEN4.0 (a SealEveL EquatioN solver) to investigate the influence of GIA on vertical land motions and sea-level changes in eastern North America. Further, we evaluate the uncertainties associated with the lithospheric thickness and viscosity structure using an ensemble modeling approach (129,956 total simulations). We identify the best-fitting rheological profiles by comparing modeled vertical displacements to vertical velocity rates derived from Global Positioning System (GPS). We find a general pattern of subsidence (causing accelerated relative sea-level rise) in the eastern United States region and uplift (causing relative sea-level fall) in the eastern Canada region consistent with previous studies for two tested ice sheet models (ICE-6G(VM5a) and ICE-7G(VM7)). Overall, we find lower rates of modeled vertical displacement using ICE-6G(VM5a) compared with ICE-7G(VM7), which produces lower residuals when compared with the GPS-derived vertical velocity rates. Our ensemble analysis identifies adjustments to the nominal VM5a and VM7 viscosity models that improve fits to the GPS-imaged vertical velocity rates throughout eastern North America and on the North American Atlantic Coast. The differences in our best-fitting models for inland versus coastal regions highlight the importance of exploring lateral viscosity variations for GIA modeling throughout North America and elsewhere.

中文翻译：

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冰川等静压平差驱动的北美东部垂直位移和海平面变化：一种集成建模方法


冰川等静压校正 （GIA） 描述了固体地球、海洋和引力场对冰川周期期间冰盖时空演变的响应。当今整个北美东部的垂直位移和海平面变化各不相同，以响应末次冰盛期后劳伦蒂德冰盖的融化。我们使用开源软件 SELEN4.0（SealEveL EquatioN 求解器）来研究 GIA 对北美东部陆地垂直运动和海平面变化的影响。此外，我们使用集成建模方法（总共 129,956 次模拟）评估了与岩石圈厚度和粘度结构相关的不确定性。我们通过将建模的垂直位移与来自全球定位系统 （GPS） 的垂直速度率进行比较来确定最合适的流变学剖面。我们发现美国东部地区沉降（导致相对海平面加速上升）和加拿大东部地区隆起（导致相对海平面下降）的一般模式与之前对两个测试冰盖模型（ICE-6G（VM5a）和 ICE-7G（VM7））的研究一致。总体而言，我们发现与 ICE-7G（VM7） 相比，使用 ICE-6G （VM5a） 建模的垂直位移率较低，与 GPS 衍生的垂直速度率相比，ICE-7G 产生的残差较低。我们的集成分析确定了对标称 VM5a 和 VM7 粘度模型的调整，这些调整提高了对整个北美东部和北美大西洋沿岸的 GPS 成像垂直速度率的拟合。我们在内陆和沿海地区的最佳拟合模型中的差异凸显了在整个北美和其他地方探索 GIA 建模的横向粘度变化的重要性。