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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2023
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ftleibnizopen:oai:oai.leibnizopen.de:w9JEfYoBNQPDO7WIL3sf 2023-10-09T21:45:10+02:00 Timescales of outlet-glacier flow with negligible basal friction: Theory, observations and modeling Feldmann, Johannes Levermann, Anders 2023 application/pdf https://oa.tib.eu/renate/handle/123456789/12287 https://doi.org/10.34657/11319 eng eng Katlenburg-Lindau : Copernicus CC BY 4.0 Unported https://creativecommons.org/licenses/by/4.0 The Cryosphere 17 (2023), Nr. 1 flow field friction glacier flow ice flow observational method sea level change timescale Antarctica 910 article Text 2023 ftleibnizopen https://doi.org/10.34657/11319 2023-09-10T23:35:18Z 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 LeibnizOpen (The Leibniz Association) 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) |
institution |
Open Polar |
collection |
LeibnizOpen (The Leibniz Association) |
op_collection_id |
ftleibnizopen |
language |
English |
topic |
flow field friction glacier flow ice flow observational method sea level change timescale Antarctica 910 |
spellingShingle |
flow field friction glacier flow ice flow observational method sea level change timescale Antarctica 910 Feldmann, Johannes Levermann, Anders Timescales of outlet-glacier flow with negligible basal friction: Theory, observations and modeling |
topic_facet |
flow field friction glacier flow ice flow observational method sea level change timescale Antarctica 910 |
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 |
Feldmann, Johannes Levermann, Anders |
author_facet |
Feldmann, Johannes Levermann, Anders |
author_sort |
Feldmann, Johannes |
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 |
Katlenburg-Lindau : Copernicus |
publishDate |
2023 |
url |
https://oa.tib.eu/renate/handle/123456789/12287 https://doi.org/10.34657/11319 |
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 17 (2023), Nr. 1 |
op_rights |
CC BY 4.0 Unported https://creativecommons.org/licenses/by/4.0 |
op_doi |
https://doi.org/10.34657/11319 |
_version_ |
1779316426018914304 |