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A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity
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| Zeitschriftentitel: | The Cryosphere |
|---|---|
| Personen und Körperschaften: | , , , |
| In: | The Cryosphere, 14, 2020, 1, S. 211-227 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
Copernicus GmbH
|
| Schlagwörter: |
| author_facet |
Joughin, Ian Shean, David E. Smith, Benjamin E. Floricioiu, Dana Joughin, Ian Shean, David E. Smith, Benjamin E. Floricioiu, Dana |
|---|---|
| author |
Joughin, Ian Shean, David E. Smith, Benjamin E. Floricioiu, Dana |
| spellingShingle |
Joughin, Ian Shean, David E. Smith, Benjamin E. Floricioiu, Dana The Cryosphere A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity Earth-Surface Processes Water Science and Technology |
| author_sort |
joughin, ian |
| spelling |
Joughin, Ian Shean, David E. Smith, Benjamin E. Floricioiu, Dana 1994-0424 Copernicus GmbH Earth-Surface Processes Water Science and Technology http://dx.doi.org/10.5194/tc-14-211-2020 <jats:p>Abstract. The speed of Greenland's fastest glacier, Jakobshavn Isbræ, has varied substantially since its speed-up in the late 1990s. Here we present observations of surface velocity, mélange rigidity, and surface elevation to examine its behaviour over the last decade. Consistent with earlier results, we find a pronounced cycle of summer speed-up and thinning followed by winter slowdown and thickening. There were extended periods of rigid mélange in the winters of 2016–2017 and 2017–2018, concurrent with terminus advances ∼6 km farther than in the several winters prior. These terminus advances to shallower depths caused slowdowns, leading to substantial thickening, as has been noted elsewhere. The extended periods of rigid mélange coincide well with a period of cooler waters in Disko Bay. Thus, along with the relative timing of the seasonal slowdown, our results suggest that the ocean's dominant influence on Jakobshavn Isbræ is through its effect on winter mélange rigidity, rather than summer submarine melting. The elevation time series also reveals that in summers when the area upstream of the terminus approaches flotation, large surface depressions can form, which eventually become the detachment points for major calving events. It appears that as elevations approach flotation, basal crevasses can form, which initiates a necking process that forms the depressions. The elevation data also show that steep cliffs often evolve into short floating extensions, rather than collapsing catastrophically due to brittle failure. Finally, summer 2019 speeds were slightly faster than the prior two summers, leaving it unclear whether the slowdown is ending. </jats:p> A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity The Cryosphere |
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| title |
A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_unstemmed |
A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_full |
A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_fullStr |
A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_full_unstemmed |
A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_short |
A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_sort |
a decade of variability on jakobshavn isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| topic |
Earth-Surface Processes Water Science and Technology |
| url |
http://dx.doi.org/10.5194/tc-14-211-2020 |
| publishDate |
2020 |
| physical |
211-227 |
| description |
<jats:p>Abstract. The speed of Greenland's fastest glacier, Jakobshavn Isbræ, has varied substantially since its speed-up in the late 1990s. Here
we present observations of surface velocity, mélange rigidity, and
surface elevation to examine its behaviour over the last decade. Consistent
with earlier results, we find a pronounced cycle of summer speed-up and
thinning followed by winter slowdown and thickening. There were extended
periods of rigid mélange in the winters of 2016–2017 and 2017–2018,
concurrent with terminus advances ∼6 km farther than in the
several winters prior. These terminus advances to shallower depths caused
slowdowns, leading to substantial thickening, as has been noted elsewhere.
The extended periods of rigid mélange coincide well with a period of
cooler waters in Disko Bay. Thus, along with the relative timing of the
seasonal slowdown, our results suggest that the ocean's dominant influence
on Jakobshavn Isbræ is through its effect on winter mélange rigidity,
rather than summer submarine melting. The elevation time series also reveals
that in summers when the area upstream of the terminus approaches flotation,
large surface depressions can form, which eventually become the detachment
points for major calving events. It appears that as elevations approach
flotation, basal crevasses can form, which initiates a necking process that
forms the depressions. The elevation data also show that steep cliffs often
evolve into short floating extensions, rather than collapsing
catastrophically due to brittle failure. Finally, summer 2019 speeds were
slightly faster than the prior two summers, leaving it unclear whether the
slowdown is ending.
</jats:p> |
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| author | Joughin, Ian, Shean, David E., Smith, Benjamin E., Floricioiu, Dana |
| author_facet | Joughin, Ian, Shean, David E., Smith, Benjamin E., Floricioiu, Dana, Joughin, Ian, Shean, David E., Smith, Benjamin E., Floricioiu, Dana |
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| description | <jats:p>Abstract. The speed of Greenland's fastest glacier, Jakobshavn Isbræ, has varied substantially since its speed-up in the late 1990s. Here we present observations of surface velocity, mélange rigidity, and surface elevation to examine its behaviour over the last decade. Consistent with earlier results, we find a pronounced cycle of summer speed-up and thinning followed by winter slowdown and thickening. There were extended periods of rigid mélange in the winters of 2016–2017 and 2017–2018, concurrent with terminus advances ∼6 km farther than in the several winters prior. These terminus advances to shallower depths caused slowdowns, leading to substantial thickening, as has been noted elsewhere. The extended periods of rigid mélange coincide well with a period of cooler waters in Disko Bay. Thus, along with the relative timing of the seasonal slowdown, our results suggest that the ocean's dominant influence on Jakobshavn Isbræ is through its effect on winter mélange rigidity, rather than summer submarine melting. The elevation time series also reveals that in summers when the area upstream of the terminus approaches flotation, large surface depressions can form, which eventually become the detachment points for major calving events. It appears that as elevations approach flotation, basal crevasses can form, which initiates a necking process that forms the depressions. The elevation data also show that steep cliffs often evolve into short floating extensions, rather than collapsing catastrophically due to brittle failure. Finally, summer 2019 speeds were slightly faster than the prior two summers, leaving it unclear whether the slowdown is ending. </jats:p> |
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| spelling | Joughin, Ian Shean, David E. Smith, Benjamin E. Floricioiu, Dana 1994-0424 Copernicus GmbH Earth-Surface Processes Water Science and Technology http://dx.doi.org/10.5194/tc-14-211-2020 <jats:p>Abstract. The speed of Greenland's fastest glacier, Jakobshavn Isbræ, has varied substantially since its speed-up in the late 1990s. Here we present observations of surface velocity, mélange rigidity, and surface elevation to examine its behaviour over the last decade. Consistent with earlier results, we find a pronounced cycle of summer speed-up and thinning followed by winter slowdown and thickening. There were extended periods of rigid mélange in the winters of 2016–2017 and 2017–2018, concurrent with terminus advances ∼6 km farther than in the several winters prior. These terminus advances to shallower depths caused slowdowns, leading to substantial thickening, as has been noted elsewhere. The extended periods of rigid mélange coincide well with a period of cooler waters in Disko Bay. Thus, along with the relative timing of the seasonal slowdown, our results suggest that the ocean's dominant influence on Jakobshavn Isbræ is through its effect on winter mélange rigidity, rather than summer submarine melting. The elevation time series also reveals that in summers when the area upstream of the terminus approaches flotation, large surface depressions can form, which eventually become the detachment points for major calving events. It appears that as elevations approach flotation, basal crevasses can form, which initiates a necking process that forms the depressions. The elevation data also show that steep cliffs often evolve into short floating extensions, rather than collapsing catastrophically due to brittle failure. Finally, summer 2019 speeds were slightly faster than the prior two summers, leaving it unclear whether the slowdown is ending. </jats:p> A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity The Cryosphere |
| spellingShingle | Joughin, Ian, Shean, David E., Smith, Benjamin E., Floricioiu, Dana, The Cryosphere, A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity, Earth-Surface Processes, Water Science and Technology |
| title | A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_full | A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_fullStr | A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_full_unstemmed | A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_short | A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_sort | a decade of variability on jakobshavn isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| title_unstemmed | A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity |
| topic | Earth-Surface Processes, Water Science and Technology |
| url | http://dx.doi.org/10.5194/tc-14-211-2020 |