Meltwater Orientations Modify Seismic Anisotropy in Temperate IceGeophysical Research Letters
Seismology is increasingly used to infer the magnitude and direction of glacial ice flow. However, the effects of interstitial meltwater on seismic properties remain poorly constrained. Here, we extend previous studies on seismic anisotropy in temperate ices to consider the role of melt preferred or...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/366178 |
| Acceso en línea: | http://hdl.handle.net/10261/366178 |
| Access Level: | acceso abierto |
| Palabra clave: | Cryoseismology Melt network orientation Ice flow Temperate ice Seismic anisotropy Ice microstructure |
| Sumario: | Seismology is increasingly used to infer the magnitude and direction of glacial ice flow. However, the effects of interstitial meltwater on seismic properties remain poorly constrained. Here, we extend previous studies on seismic anisotropy in temperate ices to consider the role of melt preferred orientation (MPO). We used the ELLE numerical toolbox to simulate microstructural shear deformation of temperate ice with variable MPO strength and orientation, and calculated the effective seismic properties of these numerical ice-melt aggregates. Our models demonstrate that even 3.5% melt volume is sufficient to rotate fast directions by up to 90 degrees, to increase Vp anisotropy by up to +110%, and to modify Vs anisotropy by -9 to +36%. These effects are especially prominent at strain rates >= 3.17 x 10-12 s-1. MPO may thus obscure the geophysical signatures of temperate ice flow in regions of rapid ice discharge, and is therefore pivotal for understanding ice mass loss. Ice on Earth is pulled toward the sea by gravity, contributing to global mean sea level rise. To better understand the flow, or movement, of ice at the continent scale, geophysical surveys are increasingly being used to measure the microscopic alignment ("fabric") of ice crystals, since ice with a strong fabric flows more readily. However, in temperate regions close to the ice melting point, melt pockets may also become aligned, creating additional macroscopic geophysical signatures. Here, we use numerical simulations to examine the combined effects of ice crystal fabric and melt alignment on the geophysical (seismic) properties of ice containing small amounts of melt. We show that melt can change the seismic fast direction (related to the inferred flow direction) of ice by up to 90 degrees, particularly as the volume of melt exceeds 3.5%, and that different melt orientations can either enhance or diminish the anisotropy-based estimates of flow that some studies use to predict ice mass loss. These effects are especially prominent in faster-flowing ice, highly relevant to ice mass loss in warming regions. Geophysical studies that do not account for melt orientation may therefore produce incorrect estimates of flow, leading to inaccuracies in future climate models. We used simulations of deforming temperate ice to show that the alignment of interstitial meltwater changes bulk seismic properties The amount of melt required to significantly modify seismic properties is at least 50% lower than previously reported Melt should be considered when using seismic and radar anisotropy to interpret viscous ice deformation and enhancement |
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