Influence of meltwater on Greenland Ice Sheet dynamics
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2017 Seasonal fluxes of meltwater control ice-flow processes across the Greenland Ice Sheet ablation zone an...
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Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/9251 2023-05-15T16:27:05+02:00 Influence of meltwater on Greenland Ice Sheet dynamics Stevens, Laura A. 2017-09 https://hdl.handle.net/1912/9251 en_US eng Massachusetts Institute of Technology and Woods Hole Oceanographic Institution WHOI Theses https://hdl.handle.net/1912/9251 doi:10.1575/1912/9251 doi:10.1575/1912/9251 Thesis 2017 ftwhoas https://doi.org/10.1575/1912/9251 2022-05-28T22:59:59Z Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2017 Seasonal fluxes of meltwater control ice-flow processes across the Greenland Ice Sheet ablation zone and subglacial discharge at marine-terminating outlet glaciers. With the increase in annual ice sheet meltwater production observed over recent decades and predicted into future decades, understanding mechanisms driving the hourly to decadal impact of meltwater on ice flow is critical for predicting Greenland Ice Sheet dynamic mass loss. This thesis investigates a wide range of meltwater-driven processes using empirical and theoretical methods for a region of the western margin of the Greenland Ice Sheet. I begin with an examination of the seasonal and annual ice flow record for the region using in situ observations of ice flow from a network of Global Positioning System (GPS) stations. Annual velocities decrease over the seven-year time-series at a rate consistent with the negative trend in annual velocities observed in neighboring regions. Using observations from the same GPS network, I next determine the trigger mechanism for rapid drainage of a supraglacial lake. In three consecutive years, I find precursory basal slip and uplift in the lake basin generates tensile stresses that promote hydrofracture beneath the lake. As these precursors are likely associated with the introduction of meltwater to the bed through neighboring moulin systems, our results imply that lakes may be less able to drain in the less crevassed, interior regions of the ice sheet. Expanding spatial scales to the full ablation zone, I then use a numerical model of subglacial hydrology to test whether model-derived effective pressures exhibit the theorized inverse relationship with melt-season ice sheet surface velocities. Finally, I pair near-ice fjord hydrographic observations with modeled and observed subglacial discharge for the Saqqardliup ... Thesis Greenland Ice Sheet Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Greenland Ice Fjord ENVELOPE(-37.694,-37.694,-54.060,-54.060) Woods Hole, MA |
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Open Polar |
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Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
op_collection_id |
ftwhoas |
language |
English |
description |
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2017 Seasonal fluxes of meltwater control ice-flow processes across the Greenland Ice Sheet ablation zone and subglacial discharge at marine-terminating outlet glaciers. With the increase in annual ice sheet meltwater production observed over recent decades and predicted into future decades, understanding mechanisms driving the hourly to decadal impact of meltwater on ice flow is critical for predicting Greenland Ice Sheet dynamic mass loss. This thesis investigates a wide range of meltwater-driven processes using empirical and theoretical methods for a region of the western margin of the Greenland Ice Sheet. I begin with an examination of the seasonal and annual ice flow record for the region using in situ observations of ice flow from a network of Global Positioning System (GPS) stations. Annual velocities decrease over the seven-year time-series at a rate consistent with the negative trend in annual velocities observed in neighboring regions. Using observations from the same GPS network, I next determine the trigger mechanism for rapid drainage of a supraglacial lake. In three consecutive years, I find precursory basal slip and uplift in the lake basin generates tensile stresses that promote hydrofracture beneath the lake. As these precursors are likely associated with the introduction of meltwater to the bed through neighboring moulin systems, our results imply that lakes may be less able to drain in the less crevassed, interior regions of the ice sheet. Expanding spatial scales to the full ablation zone, I then use a numerical model of subglacial hydrology to test whether model-derived effective pressures exhibit the theorized inverse relationship with melt-season ice sheet surface velocities. Finally, I pair near-ice fjord hydrographic observations with modeled and observed subglacial discharge for the Saqqardliup ... |
format |
Thesis |
author |
Stevens, Laura A. |
spellingShingle |
Stevens, Laura A. Influence of meltwater on Greenland Ice Sheet dynamics |
author_facet |
Stevens, Laura A. |
author_sort |
Stevens, Laura A. |
title |
Influence of meltwater on Greenland Ice Sheet dynamics |
title_short |
Influence of meltwater on Greenland Ice Sheet dynamics |
title_full |
Influence of meltwater on Greenland Ice Sheet dynamics |
title_fullStr |
Influence of meltwater on Greenland Ice Sheet dynamics |
title_full_unstemmed |
Influence of meltwater on Greenland Ice Sheet dynamics |
title_sort |
influence of meltwater on greenland ice sheet dynamics |
publisher |
Massachusetts Institute of Technology and Woods Hole Oceanographic Institution |
publishDate |
2017 |
url |
https://hdl.handle.net/1912/9251 |
long_lat |
ENVELOPE(-37.694,-37.694,-54.060,-54.060) |
geographic |
Greenland Ice Fjord |
geographic_facet |
Greenland Ice Fjord |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
doi:10.1575/1912/9251 |
op_relation |
WHOI Theses https://hdl.handle.net/1912/9251 doi:10.1575/1912/9251 |
op_doi |
https://doi.org/10.1575/1912/9251 |
op_publisher_place |
Woods Hole, MA |
_version_ |
1766016140599885824 |