Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling
The timescales of the flow and retreat of Greenland's and Antarctica's outlet glaciers and their potential instabilities are arguably the largest uncertainty in future sea-level projections. Here we derive a scaling relation that allows the comparison of the timescales of observed complex...
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Copernicus Publications
2023
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Online Access: | https://doi.org/10.5194/tc-17-327-2023 https://doaj.org/article/6e828b7c83434e65a6032013ff7b65a6 |
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ftdoajarticles:oai:doaj.org/article:6e828b7c83434e65a6032013ff7b65a6 2023-05-15T13:49:54+02:00 Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling J. Feldmann A. Levermann 2023-01-01T00:00:00Z https://doi.org/10.5194/tc-17-327-2023 https://doaj.org/article/6e828b7c83434e65a6032013ff7b65a6 EN eng Copernicus Publications https://tc.copernicus.org/articles/17/327/2023/tc-17-327-2023.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-17-327-2023 1994-0416 1994-0424 https://doaj.org/article/6e828b7c83434e65a6032013ff7b65a6 The Cryosphere, Vol 17, Pp 327-348 (2023) Environmental sciences GE1-350 Geology QE1-996.5 article 2023 ftdoajarticles https://doi.org/10.5194/tc-17-327-2023 2023-01-29T01:30:11Z The timescales of the flow and retreat of Greenland's and Antarctica's outlet glaciers and their potential instabilities are arguably the largest uncertainty in future sea-level projections. Here we derive a scaling relation that allows the comparison of the timescales of observed complex ice flow fields with geometric similarity. The scaling relation is derived under the assumption of fast, laterally confined, geometrically similar outlet-glacier flow over a slippery bed, i.e., with negligible basal friction. According to the relation, the time scaling of the outlet flow is determined by the product of the inverse of (1) the fourth power of the width-to-length ratio of its confinement, (2) the third power of the confinement depth and (3) the temperature-dependent ice softness. For the outflow at the grounding line of streams with negligible basal friction, this means that the volume flux is proportional to the ice softness and the bed depth, but goes with the fourth power of the gradient of the bed and with the fifth power of the width of the stream. We show that the theoretically derived scaling relation is supported by the observed velocity scaling of outlet glaciers across Greenland as well as by idealized numerical simulations of marine ice-sheet instabilities (MISIs) as found in Antarctica. Assuming that changes in the ice-flow velocity due to ice-dynamic imbalance are proportional to the equilibrium velocity, we combine the scaling relation with a statistical analysis of the topography of 13 MISI-prone Antarctic outlets. Under these assumptions, the timescales in response to a potential destabilization are fastest for Thwaites Glacier in West Antarctica and Mellor, Ninnis and Cook Glaciers in East Antarctica; between 16 and 67 times faster than for Pine Island Glacier. While the applicability of our results is limited by several strong assumptions, the utilization and potential further development of the presented scaling approach may help to constrain timescale estimates of outlet-glacier flow, ... Article in Journal/Newspaper Antarc* Antarctic Antarctica East Antarctica glacier Greenland Ice Sheet Pine Island Pine Island Glacier The Cryosphere Thwaites Glacier West Antarctica Directory of Open Access Journals: DOAJ Articles Antarctic East Antarctica West Antarctica Greenland Pine Island Glacier ENVELOPE(-101.000,-101.000,-75.000,-75.000) Thwaites Glacier ENVELOPE(-106.750,-106.750,-75.500,-75.500) Mellor ENVELOPE(-114.944,-114.944,60.714,60.714) Misi ENVELOPE(26.683,26.683,66.617,66.617) The Cryosphere 17 1 327 348 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
spellingShingle |
Environmental sciences GE1-350 Geology QE1-996.5 J. Feldmann A. Levermann Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
The timescales of the flow and retreat of Greenland's and Antarctica's outlet glaciers and their potential instabilities are arguably the largest uncertainty in future sea-level projections. Here we derive a scaling relation that allows the comparison of the timescales of observed complex ice flow fields with geometric similarity. The scaling relation is derived under the assumption of fast, laterally confined, geometrically similar outlet-glacier flow over a slippery bed, i.e., with negligible basal friction. According to the relation, the time scaling of the outlet flow is determined by the product of the inverse of (1) the fourth power of the width-to-length ratio of its confinement, (2) the third power of the confinement depth and (3) the temperature-dependent ice softness. For the outflow at the grounding line of streams with negligible basal friction, this means that the volume flux is proportional to the ice softness and the bed depth, but goes with the fourth power of the gradient of the bed and with the fifth power of the width of the stream. We show that the theoretically derived scaling relation is supported by the observed velocity scaling of outlet glaciers across Greenland as well as by idealized numerical simulations of marine ice-sheet instabilities (MISIs) as found in Antarctica. Assuming that changes in the ice-flow velocity due to ice-dynamic imbalance are proportional to the equilibrium velocity, we combine the scaling relation with a statistical analysis of the topography of 13 MISI-prone Antarctic outlets. Under these assumptions, the timescales in response to a potential destabilization are fastest for Thwaites Glacier in West Antarctica and Mellor, Ninnis and Cook Glaciers in East Antarctica; between 16 and 67 times faster than for Pine Island Glacier. While the applicability of our results is limited by several strong assumptions, the utilization and potential further development of the presented scaling approach may help to constrain timescale estimates of outlet-glacier flow, ... |
format |
Article in Journal/Newspaper |
author |
J. Feldmann A. Levermann |
author_facet |
J. Feldmann A. Levermann |
author_sort |
J. Feldmann |
title |
Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling |
title_short |
Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling |
title_full |
Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling |
title_fullStr |
Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling |
title_full_unstemmed |
Timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling |
title_sort |
timescales of outlet-glacier flow with negligible basal friction: theory, observations and modeling |
publisher |
Copernicus Publications |
publishDate |
2023 |
url |
https://doi.org/10.5194/tc-17-327-2023 https://doaj.org/article/6e828b7c83434e65a6032013ff7b65a6 |
long_lat |
ENVELOPE(-101.000,-101.000,-75.000,-75.000) ENVELOPE(-106.750,-106.750,-75.500,-75.500) ENVELOPE(-114.944,-114.944,60.714,60.714) ENVELOPE(26.683,26.683,66.617,66.617) |
geographic |
Antarctic East Antarctica West Antarctica Greenland Pine Island Glacier Thwaites Glacier Mellor Misi |
geographic_facet |
Antarctic East Antarctica West Antarctica Greenland Pine Island Glacier Thwaites Glacier Mellor Misi |
genre |
Antarc* Antarctic Antarctica East Antarctica glacier Greenland Ice Sheet Pine Island Pine Island Glacier The Cryosphere Thwaites Glacier West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica East Antarctica glacier Greenland Ice Sheet Pine Island Pine Island Glacier The Cryosphere Thwaites Glacier West Antarctica |
op_source |
The Cryosphere, Vol 17, Pp 327-348 (2023) |
op_relation |
https://tc.copernicus.org/articles/17/327/2023/tc-17-327-2023.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-17-327-2023 1994-0416 1994-0424 https://doaj.org/article/6e828b7c83434e65a6032013ff7b65a6 |
op_doi |
https://doi.org/10.5194/tc-17-327-2023 |
container_title |
The Cryosphere |
container_volume |
17 |
container_issue |
1 |
container_start_page |
327 |
op_container_end_page |
348 |
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1766252499098927104 |