The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers
<p>The dense mixture of iceberg of various sizes and sea ice observed in many of Greenland's fjords, called ice mélange (<i>sikussak</i> in Greenlandic), has been shown to have a significant impact on the dynamics of several Greenland tidewater glaciers, mainly through the sea...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-01-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/17/309/2023/tc-17-309-2023.pdf |
| _version_ | 1797945425300291584 |
|---|---|
| author | A. Wehrlé M. P. Lüthi A. Vieli |
| author_facet | A. Wehrlé M. P. Lüthi A. Vieli |
| author_sort | A. Wehrlé |
| collection | DOAJ |
| description | <p>The dense mixture of iceberg of various sizes and sea ice observed
in many of Greenland's fjords, called ice mélange (<i>sikussak</i> 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<span class="inline-formula"><sup>−1</sup></span>. We found that 87 % of the IMW episodes occurred prior to a
calving event visible in spaceborne observations and that <span class="inline-formula">∼75</span> %
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 floes without
fluctuating external forcing can reproduce IMW events and their
cyclic influence and explain observed propagation speeds. These
results further support our observations in characterizing the IMW
process as self-sustained through the existence of an IMW–calving
feedback. This study therefore highlights the importance of
short-term ice mélange dynamics in the longer-term evolution of
Greenland outlet glaciers.</p> |
| first_indexed | 2024-04-10T20:55:57Z |
| format | Article |
| id | doaj.art-bb63635d39e648269ad595ffc721e226 |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-04-10T20:55:57Z |
| publishDate | 2023-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-bb63635d39e648269ad595ffc721e2262023-01-23T06:45:12ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242023-01-011730932610.5194/tc-17-309-2023The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciersA. WehrléM. P. LüthiA. Vieli<p>The dense mixture of iceberg of various sizes and sea ice observed in many of Greenland's fjords, called ice mélange (<i>sikussak</i> 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<span class="inline-formula"><sup>−1</sup></span>. We found that 87 % of the IMW episodes occurred prior to a calving event visible in spaceborne observations and that <span class="inline-formula">∼75</span> % 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 floes without fluctuating external forcing can reproduce IMW events and their cyclic influence and explain observed propagation speeds. These results further support our observations in characterizing the IMW process as self-sustained through the existence of an IMW–calving feedback. This study therefore highlights the importance of short-term ice mélange dynamics in the longer-term evolution of Greenland outlet glaciers.</p>https://tc.copernicus.org/articles/17/309/2023/tc-17-309-2023.pdf |
| spellingShingle | A. Wehrlé M. P. Lüthi A. Vieli The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers The Cryosphere |
| title | 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_short | The control of short-term ice mélange weakening episodes on calving activity at major Greenland outlet glaciers |
| title_sort | control of short term ice melange weakening episodes on calving activity at major greenland outlet glaciers |
| url | https://tc.copernicus.org/articles/17/309/2023/tc-17-309-2023.pdf |
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