Resolving GIA in response to modern and future ice loss at marine grounding lines in West Antarctica
Resolving GIA in response to modern and future ice loss at marine grounding lines in West Antarctica
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解决 GIA 问题，以应对南极洲西部海洋接地线现代和未来的冰损失
DOI：
10.5194/tc-2021-232
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
H. K. Han
中科院分区：
文献类型：
--
作者：
J. Wan;N. Gomez;K. Latychev;H. K. Han
摘要。为了解释卫星、地球物理和地质记录，以及评估地球变形和海平面变化对海洋冰盖接地线的反馈，需要在冰冻圈中进行精确的冰川均衡调整（GIA）模拟。在南极洲西部活动冰损失地区评估GIA尤其具有挑战性，因为冰是由横向变化的地幔粘度所支撑的，其粘度比全球平均水平低几个数量级，导致固体地球对正在进行和未来的冰盖退缩的响应更快，更局部，因此需要包含三维粘弹性地球结构的GIA模型。GIA模型的改进允许以亚公里分辨率计算地球对表面冰载荷的粘弹性响应，冰盖模型和观测产品现在以相当前所未有的细节为GIA模型提供输入。然而，在模型中捕获GIA所需的分辨率仍然知之甚少，并且高分辨率计算需要大量的计算费用。本文采用基于最近地震层析成像和大地测量数据的一系列地球结构模型的三维GIA模型，全面分析了网格分辨率对南极洲西部阿蒙森海（ASE） GIA预测的影响。通过对空间隔离冰荷载变化的亚公里分辨率的理想灵敏度测试，我们发现需要约3倍荷载半径的网格分辨率才能准确捕获地球的弹性响应。然而，当我们考虑基于现代观测记录和未来冰盖模型预估的更现实的、空间上连贯的冰损失情景，并采用粘弹性地球时，我们发现，即使输入的冰模型在1公里网格上，在7.5公里网格上，沿接地线的误差可以小于5%，在3.75公里网格上，误差也可以小于2%。此外，我们还表明，日纬带下方的低地幔粘度导致粘性变形，这有助于在年代际时间尺度上的仪器记录，并在21世纪末等于或主导弹性效应。我们的研究结果表明，在我们考虑的1.9-15 km分辨率范围内，与忽略粘性效应和所采用的地幔粘性结构的不确定性的影响相比，在该区域采用粗网格所产生的误差可以忽略不计。
Abstract. Accurate glacial isostatic adjustment (GIA) modeling in the cryosphere is required for interpreting satellite, geophysical and geological records and to assess the feedbacks of Earth deformation and sea level change on marine ice-sheet grounding lines. Assessing GIA in areas of active ice loss in West Antarctica is particularly challenging because the ice is underlain by laterally varying mantle viscosities that are up to several orders of magnitude lower than the global average, leading to a faster and more localized response of the solid Earth to ongoing and future ice sheet retreat and necessitating GIA models that incorporate 3-D viscoelastic Earth structure. Improvements to GIA models allow for computation of the viscoelastic response of the Earth to surface ice loading at sub-kilometre resolution and ice-sheet models and observational products now provide the inputs to GIA models at comparably unprecedented detail. However, the resolution required to capture GIA in models remains poorly understood, and high-resolution calculations come at heavy computational expense. We adopt a 3-D GIA model with a range of Earth structure models based on recent seismic tomography and geodetic data to perform a comprehensive analysis of the influence of grid resolution on predictions of GIA in the Amundsen Sea Embayment (ASE) in West Antarctica. Through idealized sensitivity testing down to sub-kilometre resolution with spatially isolated ice loading changes, we find that a grid resolution of ~3 times the radius of the load is required to accurately capture the elastic response of the Earth. However, when we consider more realistic, spatially coherent ice loss scenarios based on modern observational records and future ice sheet model projections and adopt a viscoelastic Earth, we find that errors of less than 5 % along the grounding line can be achieved with a 7.5 km grid, and less than 2 % with a 3.75 km grid, even when the input ice model is on a 1 km grid. Furthermore, we show that low mantle viscosities beneath the ASE lead to viscous deformation that contributes to the instrumental record on decadal timescales and equals or dominates over elastic effects by the end of the 21st century. Our findings suggest that for the range of resolutions of 1.9–15 km that we considered, the error due to adopting a coarser grid in this region is negligible compared to the effect of neglecting viscous effects and the uncertainty in the adopted mantle viscosity structure.
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作者：
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影响因子：
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发表时间：
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期刊：
Journal of Geophysical Research: Solid Earth
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DOI：
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发表时间：
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期刊：
Journal of Geophysical Research: Solid Earth
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通讯作者：
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