Thermal Convection in Ice Sheets: We look but do not see
Abstract Thermal convection in the Antarctic and Greenland ice sheets has been dismissed on the grounds that radio-echo stratigraphy is undisturbed for long distances. However, the undisturbed stratigraphy lies, for the most part, above the density inversion in polar ice sheets and therefore does no...
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Cambridge University Press (CUP)
1985
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Online Access: | http://dx.doi.org/10.1017/s0022143000004974 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000004974 |
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crcambridgeupr:10.1017/s0022143000004974 2024-03-03T08:38:12+00:00 Thermal Convection in Ice Sheets: We look but do not see Hughes, T. 1985 http://dx.doi.org/10.1017/s0022143000004974 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000004974 en eng Cambridge University Press (CUP) Journal of Glaciology volume 31, issue 107, page 39-48 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1985 crcambridgeupr https://doi.org/10.1017/s0022143000004974 2024-02-08T08:39:08Z Abstract Thermal convection in the Antarctic and Greenland ice sheets has been dismissed on the grounds that radio-echo stratigraphy is undisturbed for long distances. However, the undisturbed stratigraphy lies, for the most part, above the density inversion in polar ice sheets and therefore does not disprove convection. An echo-free zone is widespread below the density inversion, yet nobody has cited this as a strong indication that convection is indeed present at depth. A generalized Rayleigh criterion for thermal convection in elastic-viscoplastic polycrystalline solids heated from below is developed and applied to ice-sheet convection. An infinite Rayleigh number at the onset of primary creep decreases with time and becomes constant when secondary creep dominates, suggesting that any thermal buoyancy stress can initiate convection but convection cannot be sustained below a buoyancy stress of about 3 kPa. An analysis of the temperature profile down the Byrd Station core hole suggests that about 1000 m of ice below the density inversion will sustain convection. Creep along the Byrd Station strain network, radar sounding in East Antarctica, and seismic sounding in West Antarctica are examined for evidence of convective creep superimposed on advective creep. It is concluded that the evidence for convection is there, if we look for it with the intention of finding it. Article in Journal/Newspaper Antarc* Antarctic Antarctica East Antarctica Greenland Ice Sheet Journal of Glaciology West Antarctica Cambridge University Press Antarctic The Antarctic East Antarctica West Antarctica Greenland Byrd Byrd Station ENVELOPE(-119.533,-119.533,-80.017,-80.017) Journal of Glaciology 31 107 39 48 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Hughes, T. Thermal Convection in Ice Sheets: We look but do not see |
topic_facet |
Earth-Surface Processes |
description |
Abstract Thermal convection in the Antarctic and Greenland ice sheets has been dismissed on the grounds that radio-echo stratigraphy is undisturbed for long distances. However, the undisturbed stratigraphy lies, for the most part, above the density inversion in polar ice sheets and therefore does not disprove convection. An echo-free zone is widespread below the density inversion, yet nobody has cited this as a strong indication that convection is indeed present at depth. A generalized Rayleigh criterion for thermal convection in elastic-viscoplastic polycrystalline solids heated from below is developed and applied to ice-sheet convection. An infinite Rayleigh number at the onset of primary creep decreases with time and becomes constant when secondary creep dominates, suggesting that any thermal buoyancy stress can initiate convection but convection cannot be sustained below a buoyancy stress of about 3 kPa. An analysis of the temperature profile down the Byrd Station core hole suggests that about 1000 m of ice below the density inversion will sustain convection. Creep along the Byrd Station strain network, radar sounding in East Antarctica, and seismic sounding in West Antarctica are examined for evidence of convective creep superimposed on advective creep. It is concluded that the evidence for convection is there, if we look for it with the intention of finding it. |
format |
Article in Journal/Newspaper |
author |
Hughes, T. |
author_facet |
Hughes, T. |
author_sort |
Hughes, T. |
title |
Thermal Convection in Ice Sheets: We look but do not see |
title_short |
Thermal Convection in Ice Sheets: We look but do not see |
title_full |
Thermal Convection in Ice Sheets: We look but do not see |
title_fullStr |
Thermal Convection in Ice Sheets: We look but do not see |
title_full_unstemmed |
Thermal Convection in Ice Sheets: We look but do not see |
title_sort |
thermal convection in ice sheets: we look but do not see |
publisher |
Cambridge University Press (CUP) |
publishDate |
1985 |
url |
http://dx.doi.org/10.1017/s0022143000004974 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000004974 |
long_lat |
ENVELOPE(-119.533,-119.533,-80.017,-80.017) |
geographic |
Antarctic The Antarctic East Antarctica West Antarctica Greenland Byrd Byrd Station |
geographic_facet |
Antarctic The Antarctic East Antarctica West Antarctica Greenland Byrd Byrd Station |
genre |
Antarc* Antarctic Antarctica East Antarctica Greenland Ice Sheet Journal of Glaciology West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica East Antarctica Greenland Ice Sheet Journal of Glaciology West Antarctica |
op_source |
Journal of Glaciology volume 31, issue 107, page 39-48 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000004974 |
container_title |
Journal of Glaciology |
container_volume |
31 |
container_issue |
107 |
container_start_page |
39 |
op_container_end_page |
48 |
_version_ |
1792505460864057344 |