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yexuqing木虫之王 (文学泰斗)
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Hidden cascades of seismic ice stream deformation
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Hidden cascades of seismic ice stream deformation 隐藏的地震性冰流变形级联 ▲ 作者：ANDREAS FICHTNER, COEN HOFSTEDE, BRIAN L. N. KENNETT, ANDERS SVENSSON, JULIEN WESTHOFF, FABIAN WALTER, ET AL. ▲ 链接：https://www.science.org/doi/10.1126/science.adp8094 ▲摘要：冰流是海平面变化的主要调节器。然而，由于对相关过程的不完全理解，人们对冰流演变的标准粘性流动模拟的预测能力有限。 在格陵兰冰盖上，基于钻孔光纤的观测揭示了一种与粘性流动理论不符的脆性变形模式，其长度尺度与现代冰盖模型的分辨率相似：即在地表无法观测到的冰震级联效应。冰震级联在火山来源杂质附近成核，促进晶界开裂，表现为晶体尺度原初塑性的宏观形式。 保守估计表明，冰震级联或产生与大地测量值振幅相当的应变率，从而在当前冰盖模型和观测之间提供了一个可能缺失的关联机制。 ▲ Abstract：Ice streams are major regulators of sea level change. However, standard viscous flow simulations of their evolution have limited predictive power owing to incomplete understanding of involved processes. On the Greenland ice sheet, borehole fiber-optic observations revealed a brittle deformation mode that is incompatible with viscous flow, over length scales similar to the resolution of modern ice sheet models: englacial ice quake cascades that are unobservable at the surface. Nucleating near volcanism-related impurities that promote grain boundary cracking, the ice quake cascades appear as a macroscopic form of crystal-scale wild plasticity. A conservative estimate indicates that seismic cascades are likely to produce strain rates that are comparable in amplitude with those measured geodetically, providing a plausible missing link between current ice sheet models and observations. |
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