Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica
Recent seismic measurements from upper Thwaites Glacier indicate that the bed-type variability is closely related to the along-flow basal topography. In high-relief subglacial highlands, stoss sides of topographic highs have a relatively higher acoustic impedance (‘hard’ bed) with lower acoustic imp...
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| Format: | Article |
| Language: | English |
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Cambridge University Press
2019-12-01
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| Series: | Annals of Glaciology |
| Subjects: | |
| Online Access: | https://www.cambridge.org/core/product/identifier/S0260305519000326/type/journal_article |
| _version_ | 1811157315749937152 |
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| author | Atsuhiro Muto Richard B. Alley Byron R. Parizek Sridhar Anandakrishnan |
| author_facet | Atsuhiro Muto Richard B. Alley Byron R. Parizek Sridhar Anandakrishnan |
| author_sort | Atsuhiro Muto |
| collection | DOAJ |
| description | Recent seismic measurements from upper Thwaites Glacier indicate that the bed-type variability is closely related to the along-flow basal topography. In high-relief subglacial highlands, stoss sides of topographic highs have a relatively higher acoustic impedance (‘hard’ bed) with lower acoustic impedance (‘soft’ till) on lee sides. This pattern is similar to observations of many deglaciated terrains. Subglacial hydraulic-potential gradient and its divergence show a tendency for water to diverge over the stoss sides and converge into the lee sides. Convergence favors a thicker or more widespread water system, which can more efficiently decouple ice from the underlying till. Under such circumstances, till deformation does occur but, fluxes are relatively small. Till carried from the lee sides onto stoss sides of downstream bumps should couple to the ice more efficiently, increasing the ability for transport by till deformation. In turn, this suggests that steady-state till transport can be achieved if the stoss-side till layer is thin or discontinuous. In addition, the large basal shear stress generated in the highlands seems too high for a bed lubricated by a continuous although thin deforming till, suggesting till discontinuity, which would allow debris-laden ice to erode bedrock on stoss sides, supplying additional till for transport. |
| first_indexed | 2024-04-10T05:05:14Z |
| format | Article |
| id | doaj.art-cd9a19d11b31406db1c2b6264081c7a0 |
| institution | Directory Open Access Journal |
| issn | 0260-3055 1727-5644 |
| language | English |
| last_indexed | 2024-04-10T05:05:14Z |
| publishDate | 2019-12-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Annals of Glaciology |
| spelling | doaj.art-cd9a19d11b31406db1c2b6264081c7a02023-03-09T12:27:37ZengCambridge University PressAnnals of Glaciology0260-30551727-56442019-12-0160829010.1017/aog.2019.32Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West AntarcticaAtsuhiro Muto0Richard B. Alley1https://orcid.org/0000-0003-1833-0115Byron R. Parizek2Sridhar Anandakrishnan3Department of Earth and Environmental Science, Temple University, Philadelphia, PA, USA.Department of Geosciences and the Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA, USADepartment of Geosciences and the Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA, USA Geosciences and Mathematics, The Pennsylvania State University DuBois, DuBois, PA, USADepartment of Geosciences and the Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA, USARecent seismic measurements from upper Thwaites Glacier indicate that the bed-type variability is closely related to the along-flow basal topography. In high-relief subglacial highlands, stoss sides of topographic highs have a relatively higher acoustic impedance (‘hard’ bed) with lower acoustic impedance (‘soft’ till) on lee sides. This pattern is similar to observations of many deglaciated terrains. Subglacial hydraulic-potential gradient and its divergence show a tendency for water to diverge over the stoss sides and converge into the lee sides. Convergence favors a thicker or more widespread water system, which can more efficiently decouple ice from the underlying till. Under such circumstances, till deformation does occur but, fluxes are relatively small. Till carried from the lee sides onto stoss sides of downstream bumps should couple to the ice more efficiently, increasing the ability for transport by till deformation. In turn, this suggests that steady-state till transport can be achieved if the stoss-side till layer is thin or discontinuous. In addition, the large basal shear stress generated in the highlands seems too high for a bed lubricated by a continuous although thin deforming till, suggesting till discontinuity, which would allow debris-laden ice to erode bedrock on stoss sides, supplying additional till for transport.https://www.cambridge.org/core/product/identifier/S0260305519000326/type/journal_articleAntarctic glaciologyseismicsubglacial exploration geophysicssubglacial processessubglacial sediments |
| spellingShingle | Atsuhiro Muto Richard B. Alley Byron R. Parizek Sridhar Anandakrishnan Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica Annals of Glaciology Antarctic glaciology seismic subglacial exploration geophysics subglacial processes subglacial sediments |
| title | Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica |
| title_full | Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica |
| title_fullStr | Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica |
| title_full_unstemmed | Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica |
| title_short | Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica |
| title_sort | bed type variability and till dis continuity beneath thwaites glacier west antarctica |
| topic | Antarctic glaciology seismic subglacial exploration geophysics subglacial processes subglacial sediments |
| url | https://www.cambridge.org/core/product/identifier/S0260305519000326/type/journal_article |
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