| Record |
| Author |
Wittlinger Gérard, Farra Véronique, |
| Title |
Evidence of unfrozen liquids and seismic anisotropy at the base of the polar ice sheets
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Type |
Journal Article |
Year  |
2015 |
Publication |
Polar Science |
Abbreviated Journal |
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| Volume |
9 |
Issue |
1 |
Pages |
66-79 |
| Keywords |
Polar ice, Seismic anisotropy, Unfrozen liquids, |
| Abstract |
We analyze seismic data from broadband stations located on the Antarctic and Greenland ice sheets to determine polar ice seismic velocities. P-to-S converted waves at the ice/rock interface and inside the ice sheets and their multiples (the P-receiver functions) are used to estimate in-situ P-wave velocity (Vp) and P-to-S velocity ratio (Vp/Vs) of polar ice. We find that the polar ice sheets have a two-layer structure; an upper layer of variable thickness (about 2/3 of the total thickness) with seismic velocities close to the standard ice values, and a lower layer of approximately constant thickness with standard Vp but ∼25% smaller Vs. The lower layer ceiling corresponds approximately to the −30 °C isotherm. Synthetic modeling of P-receiver functions shows that strong seismic anisotropy and low vertical S velocity are needed in the lower layer. The seismic anisotropy results from the preferred orientation of ice crystal c-axes toward the vertical. The low vertical S velocity may be due to the presence of unfrozen liquids resulting from premelting at grain joints and/or melting of chemical solutions buried in the ice. The strongly preferred ice crystal orientation fabric and the unfrozen fluids may facilitate polar ice sheet basal flow. |
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133 |
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Place of Publication |
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Original Title |
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Series Title |
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Abbreviated Series Title |
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Edition |
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| ISSN |
18739652 |
ISBN |
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Conference |
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| Notes |
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Approved |
yes |
| Call Number |
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Serial |
6151 |
| Permanent link to this record |
