Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial
The lack of continental ice sheets in Alaska during the Last Glacial Maximum (LGM; 26–19 ka) has long been attributed to extensive aridity in the western Arctic. More recently, climate model outputs, a few isolated paleoclimate studies, and global paleoclimate synthesis products show mild summer tem...
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Copernicus Publications
2024
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Online Access: | https://doi.org/10.5194/cp-20-91-2024 https://doaj.org/article/65e9b1fad8b44d4d94a732be46a7ebd0 |
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ftdoajarticles:oai:doaj.org/article:65e9b1fad8b44d4d94a732be46a7ebd0 2024-02-11T09:54:50+01:00 Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial C. K. Walcott J. P. Briner J. P. Tulenko S. M. Evans 2024-01-01T00:00:00Z https://doi.org/10.5194/cp-20-91-2024 https://doaj.org/article/65e9b1fad8b44d4d94a732be46a7ebd0 EN eng Copernicus Publications https://cp.copernicus.org/articles/20/91/2024/cp-20-91-2024.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-20-91-2024 1814-9324 1814-9332 https://doaj.org/article/65e9b1fad8b44d4d94a732be46a7ebd0 Climate of the Past, Vol 20, Pp 91-106 (2024) Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 article 2024 ftdoajarticles https://doi.org/10.5194/cp-20-91-2024 2024-01-14T01:38:17Z The lack of continental ice sheets in Alaska during the Last Glacial Maximum (LGM; 26–19 ka) has long been attributed to extensive aridity in the western Arctic. More recently, climate model outputs, a few isolated paleoclimate studies, and global paleoclimate synthesis products show mild summer temperature depressions in Alaska compared to much of the high northern latitudes. This suggests the importance of limited summer temperature depressions in controlling the relatively limited glacier growth during the LGM. To explore this further, we present a new statewide map of LGM alpine glacier equilibrium line altitudes (ELAs), LGM Δ ELAs (LGM ELA anomalies relative to the Little Ice Age, LIA), and Δ ELA-based estimates of temperature depressions across Alaska to assess paleoclimate conditions. We reconstructed paleoglacier surfaces in ArcGIS to calculate ELAs using an accumulation area ratio (AAR) of 0.58 and an area–altitude balance ratio (AABR) of 1.56. We calculated LGM ELAs ( n = 480) in glaciated massifs in the state, excluding areas in southern Alaska that were covered by the Cordilleran Ice Sheet. The data show a trend of increasing ELAs from the southwest to the northeast during both the LGM and the LIA, indicating a consistent southern Bering Sea and northernmost Pacific Ocean precipitation source. Our LGM–LIA Δ ELAs from the Alaska Range, supported with limited LGM–LIA Δ ELAs from the Brooks Range and the Kigluaik Mountains, average to − 355 ± 176 m. This value is much greater than the global LGM average of ca. − 1000 m. Using a range of atmospheric lapse rates, LGM–LIA Δ ELAs in Alaska translate to summer cooling of < 2–5 ∘ C. Our results are consistent with a growing number of local climate proxy reconstructions and global data assimilation syntheses that indicate mild summer temperature across Beringia during the LGM. Limited LGM summer temperature depressions could be explained by the influence of Northern Hemisphere ice sheets on atmospheric circulation. Article in Journal/Newspaper alaska range Arctic Bering Sea Brooks Range glacier glaciers Ice Sheet Alaska Beringia Directory of Open Access Journals: DOAJ Articles Arctic Bering Sea Ela ENVELOPE(9.642,9.642,63.170,63.170) Pacific Climate of the Past 20 1 91 106 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
spellingShingle |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 C. K. Walcott J. P. Briner J. P. Tulenko S. M. Evans Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial |
topic_facet |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
description |
The lack of continental ice sheets in Alaska during the Last Glacial Maximum (LGM; 26–19 ka) has long been attributed to extensive aridity in the western Arctic. More recently, climate model outputs, a few isolated paleoclimate studies, and global paleoclimate synthesis products show mild summer temperature depressions in Alaska compared to much of the high northern latitudes. This suggests the importance of limited summer temperature depressions in controlling the relatively limited glacier growth during the LGM. To explore this further, we present a new statewide map of LGM alpine glacier equilibrium line altitudes (ELAs), LGM Δ ELAs (LGM ELA anomalies relative to the Little Ice Age, LIA), and Δ ELA-based estimates of temperature depressions across Alaska to assess paleoclimate conditions. We reconstructed paleoglacier surfaces in ArcGIS to calculate ELAs using an accumulation area ratio (AAR) of 0.58 and an area–altitude balance ratio (AABR) of 1.56. We calculated LGM ELAs ( n = 480) in glaciated massifs in the state, excluding areas in southern Alaska that were covered by the Cordilleran Ice Sheet. The data show a trend of increasing ELAs from the southwest to the northeast during both the LGM and the LIA, indicating a consistent southern Bering Sea and northernmost Pacific Ocean precipitation source. Our LGM–LIA Δ ELAs from the Alaska Range, supported with limited LGM–LIA Δ ELAs from the Brooks Range and the Kigluaik Mountains, average to − 355 ± 176 m. This value is much greater than the global LGM average of ca. − 1000 m. Using a range of atmospheric lapse rates, LGM–LIA Δ ELAs in Alaska translate to summer cooling of < 2–5 ∘ C. Our results are consistent with a growing number of local climate proxy reconstructions and global data assimilation syntheses that indicate mild summer temperature across Beringia during the LGM. Limited LGM summer temperature depressions could be explained by the influence of Northern Hemisphere ice sheets on atmospheric circulation. |
format |
Article in Journal/Newspaper |
author |
C. K. Walcott J. P. Briner J. P. Tulenko S. M. Evans |
author_facet |
C. K. Walcott J. P. Briner J. P. Tulenko S. M. Evans |
author_sort |
C. K. Walcott |
title |
Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial |
title_short |
Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial |
title_full |
Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial |
title_fullStr |
Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial |
title_full_unstemmed |
Equilibrium line altitudes of alpine glaciers in Alaska suggest Last Glacial Maximum summer temperature was 2–5 °C lower than during the pre-industrial |
title_sort |
equilibrium line altitudes of alpine glaciers in alaska suggest last glacial maximum summer temperature was 2–5 °c lower than during the pre-industrial |
publisher |
Copernicus Publications |
publishDate |
2024 |
url |
https://doi.org/10.5194/cp-20-91-2024 https://doaj.org/article/65e9b1fad8b44d4d94a732be46a7ebd0 |
long_lat |
ENVELOPE(9.642,9.642,63.170,63.170) |
geographic |
Arctic Bering Sea Ela Pacific |
geographic_facet |
Arctic Bering Sea Ela Pacific |
genre |
alaska range Arctic Bering Sea Brooks Range glacier glaciers Ice Sheet Alaska Beringia |
genre_facet |
alaska range Arctic Bering Sea Brooks Range glacier glaciers Ice Sheet Alaska Beringia |
op_source |
Climate of the Past, Vol 20, Pp 91-106 (2024) |
op_relation |
https://cp.copernicus.org/articles/20/91/2024/cp-20-91-2024.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-20-91-2024 1814-9324 1814-9332 https://doaj.org/article/65e9b1fad8b44d4d94a732be46a7ebd0 |
op_doi |
https://doi.org/10.5194/cp-20-91-2024 |
container_title |
Climate of the Past |
container_volume |
20 |
container_issue |
1 |
container_start_page |
91 |
op_container_end_page |
106 |
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1790607606988931072 |