A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial
Changes in the latitudinal position and strength of the Southern Hemisphere westerlies (SHW) are thought to be tightly coupled to important climate processes, such as cross-equatorial heat fluxes, Atlantic Meridional Overturning Circulation (AMOC), the bipolar seesaw, Southern Ocean ventilation and...
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ftdoajarticles:oai:doaj.org/article:a7dc870cc95843e1954b519c1ed4b532 2023-05-15T18:25:55+02:00 A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial S. Björck J. Sjolte K. Ljung F. Adolphi R. Flower R. H. Smittenberg M. E. Kylander T. F. Stocker S. Holmgren H. Jiang R. Muscheler Y. K. K. Afrifa J. E. Rattray N. Van der Putten 2019-11-01T00:00:00Z https://doi.org/10.5194/cp-15-1939-2019 https://doaj.org/article/a7dc870cc95843e1954b519c1ed4b532 EN eng Copernicus Publications https://www.clim-past.net/15/1939/2019/cp-15-1939-2019.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-15-1939-2019 1814-9324 1814-9332 https://doaj.org/article/a7dc870cc95843e1954b519c1ed4b532 Climate of the Past, Vol 15, Pp 1939-1958 (2019) Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 article 2019 ftdoajarticles https://doi.org/10.5194/cp-15-1939-2019 2022-12-31T12:23:44Z Changes in the latitudinal position and strength of the Southern Hemisphere westerlies (SHW) are thought to be tightly coupled to important climate processes, such as cross-equatorial heat fluxes, Atlantic Meridional Overturning Circulation (AMOC), the bipolar seesaw, Southern Ocean ventilation and atmospheric CO 2 levels. However, many uncertainties regarding magnitude, direction, and causes and effects of past SHW shifts still exist due to lack of suitable sites and scarcity of information on SHW dynamics, especially from the last glacial. Here we present a detailed hydroclimate multiproxy record from a 36.4–18.6 kyr old lake sediment sequence on Nightingale Island (NI). It is strategically located at 37 ∘ S in the central South Atlantic (SA) within the SHW belt and situated just north of the marine Subtropical Front (SF). This has enabled us to assess hydroclimate changes and their link to the regional climate development as well as to large-scale climate events in polar ice cores. The NI record exhibits a continuous impact of the SHW, recording shifts in both position and strength, and between 36 and 31 ka the westerlies show high latitudinal and strength-wise variability possibly linked to the bipolar seesaw. This was followed by 4 kyr of slightly falling temperatures, decreasing humidity and fairly southerly westerlies. After 27 ka temperatures decreased 3–4 ∘ C, marking the largest hydroclimate change with drier conditions and a variable SHW position. We note that periods with more intense and southerly-positioned SHW seem to be related to periods of increased CO 2 outgassing from the ocean, while changes in the cross-equatorial gradient during large northern temperature changes appear as the driving mechanism for the SHW shifts. Together with coeval shifts of the South Pacific westerlies, our results show that most of the Southern Hemisphere experienced simultaneous atmospheric circulation changes during the latter part of the last glacial. Finally we can conclude that multiproxy lake records from ... Article in Journal/Newspaper Southern Ocean Directory of Open Access Journals: DOAJ Articles Pacific Southern Ocean Climate of the Past 15 6 1939 1958 |
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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 S. Björck J. Sjolte K. Ljung F. Adolphi R. Flower R. H. Smittenberg M. E. Kylander T. F. Stocker S. Holmgren H. Jiang R. Muscheler Y. K. K. Afrifa J. E. Rattray N. Van der Putten A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial |
topic_facet |
Environmental pollution TD172-193.5 Environmental protection TD169-171.8 Environmental sciences GE1-350 |
description |
Changes in the latitudinal position and strength of the Southern Hemisphere westerlies (SHW) are thought to be tightly coupled to important climate processes, such as cross-equatorial heat fluxes, Atlantic Meridional Overturning Circulation (AMOC), the bipolar seesaw, Southern Ocean ventilation and atmospheric CO 2 levels. However, many uncertainties regarding magnitude, direction, and causes and effects of past SHW shifts still exist due to lack of suitable sites and scarcity of information on SHW dynamics, especially from the last glacial. Here we present a detailed hydroclimate multiproxy record from a 36.4–18.6 kyr old lake sediment sequence on Nightingale Island (NI). It is strategically located at 37 ∘ S in the central South Atlantic (SA) within the SHW belt and situated just north of the marine Subtropical Front (SF). This has enabled us to assess hydroclimate changes and their link to the regional climate development as well as to large-scale climate events in polar ice cores. The NI record exhibits a continuous impact of the SHW, recording shifts in both position and strength, and between 36 and 31 ka the westerlies show high latitudinal and strength-wise variability possibly linked to the bipolar seesaw. This was followed by 4 kyr of slightly falling temperatures, decreasing humidity and fairly southerly westerlies. After 27 ka temperatures decreased 3–4 ∘ C, marking the largest hydroclimate change with drier conditions and a variable SHW position. We note that periods with more intense and southerly-positioned SHW seem to be related to periods of increased CO 2 outgassing from the ocean, while changes in the cross-equatorial gradient during large northern temperature changes appear as the driving mechanism for the SHW shifts. Together with coeval shifts of the South Pacific westerlies, our results show that most of the Southern Hemisphere experienced simultaneous atmospheric circulation changes during the latter part of the last glacial. Finally we can conclude that multiproxy lake records from ... |
format |
Article in Journal/Newspaper |
author |
S. Björck J. Sjolte K. Ljung F. Adolphi R. Flower R. H. Smittenberg M. E. Kylander T. F. Stocker S. Holmgren H. Jiang R. Muscheler Y. K. K. Afrifa J. E. Rattray N. Van der Putten |
author_facet |
S. Björck J. Sjolte K. Ljung F. Adolphi R. Flower R. H. Smittenberg M. E. Kylander T. F. Stocker S. Holmgren H. Jiang R. Muscheler Y. K. K. Afrifa J. E. Rattray N. Van der Putten |
author_sort |
S. Björck |
title |
A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial |
title_short |
A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial |
title_full |
A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial |
title_fullStr |
A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial |
title_full_unstemmed |
A South Atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial |
title_sort |
south atlantic island record uncovers shifts in westerlies and hydroclimate during the last glacial |
publisher |
Copernicus Publications |
publishDate |
2019 |
url |
https://doi.org/10.5194/cp-15-1939-2019 https://doaj.org/article/a7dc870cc95843e1954b519c1ed4b532 |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
Climate of the Past, Vol 15, Pp 1939-1958 (2019) |
op_relation |
https://www.clim-past.net/15/1939/2019/cp-15-1939-2019.pdf https://doaj.org/toc/1814-9324 https://doaj.org/toc/1814-9332 doi:10.5194/cp-15-1939-2019 1814-9324 1814-9332 https://doaj.org/article/a7dc870cc95843e1954b519c1ed4b532 |
op_doi |
https://doi.org/10.5194/cp-15-1939-2019 |
container_title |
Climate of the Past |
container_volume |
15 |
container_issue |
6 |
container_start_page |
1939 |
op_container_end_page |
1958 |
_version_ |
1766207639530766336 |