The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers

The dense mixture of iceberg of various sizes and sea ice observed in many of Greenland's fjords, called ice mélange ( sikussak in Greenlandic), has been shown to have a significant impact on the dynamics of several Greenland tidewater glaciers, mainly through the seasonal support it provides t...

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Published in:The Cryosphere
Main Authors: A. Wehrlé, M. P. Lüthi, A. Vieli
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2023
Subjects:
Online Access:https://doi.org/10.5194/tc-17-309-2023
https://doaj.org/article/bb63635d39e648269ad595ffc721e226
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spelling ftdoajarticles:oai:doaj.org/article:bb63635d39e648269ad595ffc721e226 2023-05-15T16:21:09+02:00 The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers A. Wehrlé M. P. Lüthi A. Vieli 2023-01-01T00:00:00Z https://doi.org/10.5194/tc-17-309-2023 https://doaj.org/article/bb63635d39e648269ad595ffc721e226 EN eng Copernicus Publications https://tc.copernicus.org/articles/17/309/2023/tc-17-309-2023.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-17-309-2023 1994-0416 1994-0424 https://doaj.org/article/bb63635d39e648269ad595ffc721e226 The Cryosphere, Vol 17, Pp 309-326 (2023) Environmental sciences GE1-350 Geology QE1-996.5 article 2023 ftdoajarticles https://doi.org/10.5194/tc-17-309-2023 2023-01-29T01:30:48Z The dense mixture of iceberg of various sizes and sea ice observed in many of Greenland's fjords, called ice mélange ( sikussak in Greenlandic), has been shown to have a significant impact on the dynamics of several Greenland tidewater glaciers, mainly through the seasonal support it provides to the glacier terminus in winter. However, a clear understanding of shorter-term ice mélange dynamics is still lacking, mainly due to the high complexity and variability of the processes at play at the ice–ocean boundary. In this study, we use a combination of Sentinel-1 radar and Sentinel-2 optical satellite imagery to investigate in detail intra-seasonal ice mélange dynamics and its link to calving activity at three major outlet glaciers: Kangerdlugssuaq Glacier, Helheim Glacier and Sermeq Kujalleq in Kangia (Jakobshavn Isbræ). In those fjords, we identified recurrent ice mélange weakening (IMW) episodes consisting of the up-fjord propagation of a discontinuity between jam-packed and weaker ice mélange towards the glacier terminus. At a late stage, i.e., when the IMW front approaches the glacier terminus, these episodes were often correlated with the occurrence of large-scale calving events. The IMW process is particularly visible at the front of Kangerdlugssuaq Glacier and presents a cyclic behavior, such that we further analyzed IMW dynamics during the June–November period from 2018 to 2021 at this location. Throughout this period, we detected 30 IMW episodes with a recurrence time of 24 d, propagating over a median distance of 5.9 km and for 17 d, resulting in a median propagation speed of 400 m d −1 . We found that 87 % of the IMW episodes occurred prior to a calving event visible in spaceborne observations and that ∼75 % of all detected calving events were preceded by an IMW episode. These results therefore present the IMW process as a clear control on the calving activity of Kangerdlugssuaq Glacier. Finally, using a simple numerical model for ice mélange motion, we showed that a slightly biased random motion of ice ... Article in Journal/Newspaper glacier Greenland greenlandic Jakobshavn Jakobshavn isbræ Kangia Kujalleq Sea ice Sermeq Kujalleq The Cryosphere Tidewater Directory of Open Access Journals: DOAJ Articles Greenland Jakobshavn Isbræ ENVELOPE(-49.917,-49.917,69.167,69.167) Kujalleq ENVELOPE(-46.037,-46.037,60.719,60.719) The Cryosphere 17 1 309 326
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
A. Wehrlé
M. P. Lüthi
A. Vieli
The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers
topic_facet Environmental sciences
GE1-350
Geology
QE1-996.5
description The dense mixture of iceberg of various sizes and sea ice observed in many of Greenland's fjords, called ice mélange ( sikussak in Greenlandic), has been shown to have a significant impact on the dynamics of several Greenland tidewater glaciers, mainly through the seasonal support it provides to the glacier terminus in winter. However, a clear understanding of shorter-term ice mélange dynamics is still lacking, mainly due to the high complexity and variability of the processes at play at the ice–ocean boundary. In this study, we use a combination of Sentinel-1 radar and Sentinel-2 optical satellite imagery to investigate in detail intra-seasonal ice mélange dynamics and its link to calving activity at three major outlet glaciers: Kangerdlugssuaq Glacier, Helheim Glacier and Sermeq Kujalleq in Kangia (Jakobshavn Isbræ). In those fjords, we identified recurrent ice mélange weakening (IMW) episodes consisting of the up-fjord propagation of a discontinuity between jam-packed and weaker ice mélange towards the glacier terminus. At a late stage, i.e., when the IMW front approaches the glacier terminus, these episodes were often correlated with the occurrence of large-scale calving events. The IMW process is particularly visible at the front of Kangerdlugssuaq Glacier and presents a cyclic behavior, such that we further analyzed IMW dynamics during the June–November period from 2018 to 2021 at this location. Throughout this period, we detected 30 IMW episodes with a recurrence time of 24 d, propagating over a median distance of 5.9 km and for 17 d, resulting in a median propagation speed of 400 m d −1 . We found that 87 % of the IMW episodes occurred prior to a calving event visible in spaceborne observations and that ∼75 % of all detected calving events were preceded by an IMW episode. These results therefore present the IMW process as a clear control on the calving activity of Kangerdlugssuaq Glacier. Finally, using a simple numerical model for ice mélange motion, we showed that a slightly biased random motion of ice ...
format Article in Journal/Newspaper
author A. Wehrlé
M. P. Lüthi
A. Vieli
author_facet A. Wehrlé
M. P. Lüthi
A. Vieli
author_sort A. Wehrlé
title The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers
title_short The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers
title_full The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers
title_fullStr The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers
title_full_unstemmed The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers
title_sort control of short-term ice mélange weakening episodes on calving activity at major greenland outlet glaciers
publisher Copernicus Publications
publishDate 2023
url https://doi.org/10.5194/tc-17-309-2023
https://doaj.org/article/bb63635d39e648269ad595ffc721e226
long_lat ENVELOPE(-49.917,-49.917,69.167,69.167)
ENVELOPE(-46.037,-46.037,60.719,60.719)
geographic Greenland
Jakobshavn Isbræ
Kujalleq
geographic_facet Greenland
Jakobshavn Isbræ
Kujalleq
genre glacier
Greenland
greenlandic
Jakobshavn
Jakobshavn isbræ
Kangia
Kujalleq
Sea ice
Sermeq Kujalleq
The Cryosphere
Tidewater
genre_facet glacier
Greenland
greenlandic
Jakobshavn
Jakobshavn isbræ
Kangia
Kujalleq
Sea ice
Sermeq Kujalleq
The Cryosphere
Tidewater
op_source The Cryosphere, Vol 17, Pp 309-326 (2023)
op_relation https://tc.copernicus.org/articles/17/309/2023/tc-17-309-2023.pdf
https://doaj.org/toc/1994-0416
https://doaj.org/toc/1994-0424
doi:10.5194/tc-17-309-2023
1994-0416
1994-0424
https://doaj.org/article/bb63635d39e648269ad595ffc721e226
op_doi https://doi.org/10.5194/tc-17-309-2023
container_title The Cryosphere
container_volume 17
container_issue 1
container_start_page 309
op_container_end_page 326
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