Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation
The large-scale reorganization of deep ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contribu...
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Online Access: | http://www.osti.gov/servlets/purl/1412877 https://www.osti.gov/biblio/1412877 https://doi.org/10.1073/pnas.1704512114 |
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ftosti:oai:osti.gov:1412877 2023-07-30T03:58:11+02:00 Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation Zhang, Jiaxu Liu, Zhengyu Brady, Esther C. Oppo, Delia W. Clark, Peter U. Jahn, Alexandra Marcott, Shaun A. Lindsay, Keith 2022-03-30 application/pdf http://www.osti.gov/servlets/purl/1412877 https://www.osti.gov/biblio/1412877 https://doi.org/10.1073/pnas.1704512114 unknown http://www.osti.gov/servlets/purl/1412877 https://www.osti.gov/biblio/1412877 https://doi.org/10.1073/pnas.1704512114 doi:10.1073/pnas.1704512114 54 ENVIRONMENTAL SCIENCES 2022 ftosti https://doi.org/10.1073/pnas.1704512114 2023-07-11T09:23:11Z The large-scale reorganization of deep ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including δ 18 O of benthic foraminiferal calcite (δ 18 Oc). Here in this study, we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ 18 O evolution. Model results suggest that, in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses, while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties caused by freshwater input as suggested previously, the observed phasing difference of deep δ 18 O c likely reflects early warming of the deep northern North Atlantic by ~1.4 °C, while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong middepth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way that ocean circulation affects heat, a dynamic tracer, is considerably different from how it affects passive tracers, like δ 18 O, and call for caution when inferring water mass changes from δ 18 O c records while assuming uniform changes in deep temperatures. Other/Unknown Material Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic Southern Ocean SciTec Connect (Office of Scientific and Technical Information - OSTI, U.S. Department of Energy) Antarctic Southern Ocean Proceedings of the National Academy of Sciences 114 42 11075 11080 |
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SciTec Connect (Office of Scientific and Technical Information - OSTI, U.S. Department of Energy) |
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ftosti |
language |
unknown |
topic |
54 ENVIRONMENTAL SCIENCES |
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54 ENVIRONMENTAL SCIENCES Zhang, Jiaxu Liu, Zhengyu Brady, Esther C. Oppo, Delia W. Clark, Peter U. Jahn, Alexandra Marcott, Shaun A. Lindsay, Keith Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation |
topic_facet |
54 ENVIRONMENTAL SCIENCES |
description |
The large-scale reorganization of deep ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including δ 18 O of benthic foraminiferal calcite (δ 18 Oc). Here in this study, we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ 18 O evolution. Model results suggest that, in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses, while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties caused by freshwater input as suggested previously, the observed phasing difference of deep δ 18 O c likely reflects early warming of the deep northern North Atlantic by ~1.4 °C, while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong middepth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way that ocean circulation affects heat, a dynamic tracer, is considerably different from how it affects passive tracers, like δ 18 O, and call for caution when inferring water mass changes from δ 18 O c records while assuming uniform changes in deep temperatures. |
author |
Zhang, Jiaxu Liu, Zhengyu Brady, Esther C. Oppo, Delia W. Clark, Peter U. Jahn, Alexandra Marcott, Shaun A. Lindsay, Keith |
author_facet |
Zhang, Jiaxu Liu, Zhengyu Brady, Esther C. Oppo, Delia W. Clark, Peter U. Jahn, Alexandra Marcott, Shaun A. Lindsay, Keith |
author_sort |
Zhang, Jiaxu |
title |
Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation |
title_short |
Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation |
title_full |
Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation |
title_fullStr |
Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation |
title_full_unstemmed |
Asynchronous warming and δ 18 O evolution of deep Atlantic water masses during the last deglaciation |
title_sort |
asynchronous warming and δ 18 o evolution of deep atlantic water masses during the last deglaciation |
publishDate |
2022 |
url |
http://www.osti.gov/servlets/purl/1412877 https://www.osti.gov/biblio/1412877 https://doi.org/10.1073/pnas.1704512114 |
geographic |
Antarctic Southern Ocean |
geographic_facet |
Antarctic Southern Ocean |
genre |
Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic Southern Ocean |
genre_facet |
Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic Southern Ocean |
op_relation |
http://www.osti.gov/servlets/purl/1412877 https://www.osti.gov/biblio/1412877 https://doi.org/10.1073/pnas.1704512114 doi:10.1073/pnas.1704512114 |
op_doi |
https://doi.org/10.1073/pnas.1704512114 |
container_title |
Proceedings of the National Academy of Sciences |
container_volume |
114 |
container_issue |
42 |
container_start_page |
11075 |
op_container_end_page |
11080 |
_version_ |
1772821063127793664 |