Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates
Many glaciers are thinning rapidly beneath melt-reducing debris cover, including Kennicott Glacier in Alaska where glacier-wide maximum thinning also occurs under debris. This contradiction has been explained by melt hotspots, such as ice cliffs, scattered within the debris cover. However, melt hots...
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ftcopernicus:oai:publications.copernicus.org:tc78848 2023-05-15T16:20:10+02:00 Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates Anderson, Leif S. Armstrong, William H. Anderson, Robert S. Buri, Pascal 2021-01-19 application/pdf https://doi.org/10.5194/tc-15-265-2021 https://tc.copernicus.org/articles/15/265/2021/ eng eng doi:10.5194/tc-15-265-2021 https://tc.copernicus.org/articles/15/265/2021/ eISSN: 1994-0424 Text 2021 ftcopernicus https://doi.org/10.5194/tc-15-265-2021 2021-01-25T17:22:13Z Many glaciers are thinning rapidly beneath melt-reducing debris cover, including Kennicott Glacier in Alaska where glacier-wide maximum thinning also occurs under debris. This contradiction has been explained by melt hotspots, such as ice cliffs, scattered within the debris cover. However, melt hotspots alone cannot account for the rapid thinning at Kennicott Glacier. We consider the significance of ice cliffs, debris, and ice dynamics in addressing this outstanding problem. We collected abundant in situ measurements of debris thickness, sub-debris melt, and ice cliff backwasting, allowing for extrapolation across the debris-covered tongue (the study area and the lower 24.2 km 2 of the 387 km 2 glacier). A newly developed automatic ice cliff delineation method is the first to use only optical satellite imagery. The adaptive binary threshold method accurately estimates ice cliff coverage even where ice cliffs are small and debris color varies. Kennicott Glacier exhibits the highest fractional area of ice cliffs (11.7 %) documented to date. Ice cliffs contribute 26 % of total melt across the glacier tongue. Although the relative importance of ice cliffs to area-average melt is significant, the absolute area-averaged melt is dominated by debris. At Kennicott Glacier, glacier-wide melt rates are not maximized in the zone of maximum thinning. Declining ice discharge through time therefore explains the rapid thinning. There is more debris-covered ice in Alaska than in any other region on Earth. Through this study, Kennicott Glacier is the first glacier in Alaska, and the largest glacier globally, where melt across its debris-covered tongue has been rigorously quantified. Text glacier glaciers Alaska Copernicus Publications: E-Journals The Cryosphere 15 1 265 282 |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
Many glaciers are thinning rapidly beneath melt-reducing debris cover, including Kennicott Glacier in Alaska where glacier-wide maximum thinning also occurs under debris. This contradiction has been explained by melt hotspots, such as ice cliffs, scattered within the debris cover. However, melt hotspots alone cannot account for the rapid thinning at Kennicott Glacier. We consider the significance of ice cliffs, debris, and ice dynamics in addressing this outstanding problem. We collected abundant in situ measurements of debris thickness, sub-debris melt, and ice cliff backwasting, allowing for extrapolation across the debris-covered tongue (the study area and the lower 24.2 km 2 of the 387 km 2 glacier). A newly developed automatic ice cliff delineation method is the first to use only optical satellite imagery. The adaptive binary threshold method accurately estimates ice cliff coverage even where ice cliffs are small and debris color varies. Kennicott Glacier exhibits the highest fractional area of ice cliffs (11.7 %) documented to date. Ice cliffs contribute 26 % of total melt across the glacier tongue. Although the relative importance of ice cliffs to area-average melt is significant, the absolute area-averaged melt is dominated by debris. At Kennicott Glacier, glacier-wide melt rates are not maximized in the zone of maximum thinning. Declining ice discharge through time therefore explains the rapid thinning. There is more debris-covered ice in Alaska than in any other region on Earth. Through this study, Kennicott Glacier is the first glacier in Alaska, and the largest glacier globally, where melt across its debris-covered tongue has been rigorously quantified. |
format |
Text |
author |
Anderson, Leif S. Armstrong, William H. Anderson, Robert S. Buri, Pascal |
spellingShingle |
Anderson, Leif S. Armstrong, William H. Anderson, Robert S. Buri, Pascal Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates |
author_facet |
Anderson, Leif S. Armstrong, William H. Anderson, Robert S. Buri, Pascal |
author_sort |
Anderson, Leif S. |
title |
Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates |
title_short |
Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates |
title_full |
Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates |
title_fullStr |
Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates |
title_full_unstemmed |
Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates |
title_sort |
debris cover and the thinning of kennicott glacier, alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates |
publishDate |
2021 |
url |
https://doi.org/10.5194/tc-15-265-2021 https://tc.copernicus.org/articles/15/265/2021/ |
genre |
glacier glaciers Alaska |
genre_facet |
glacier glaciers Alaska |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-15-265-2021 https://tc.copernicus.org/articles/15/265/2021/ |
op_doi |
https://doi.org/10.5194/tc-15-265-2021 |
container_title |
The Cryosphere |
container_volume |
15 |
container_issue |
1 |
container_start_page |
265 |
op_container_end_page |
282 |
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1766007836315222016 |