Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison
The Southern Hemisphere (SH) westerly winds are thought to be critical to global ocean circulation, productivity, and carbon storage. For example, an equatorward shift in the winds, though its affect on the Southern Ocean circulation, has been suggested as the leading cause for the reduction in atmo...
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ftnerc:oai:nora.nerc.ac.uk:18845 2023-05-15T18:18:50+02:00 Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison Sime, Louise C. Kohfeld, Karen E. Le Quere, Corinne Wolff, Eric de Boer, Agatha M. Graham, Robert M. Bopp, Laurent 2013-03-15 text http://nora.nerc.ac.uk/id/eprint/18845/ https://nora.nerc.ac.uk/id/eprint/18845/1/QSR_Sime_reduced.pdf http://www.sciencedirect.com/science/article/pii/S0277379112005215 en eng Elsevier https://nora.nerc.ac.uk/id/eprint/18845/1/QSR_Sime_reduced.pdf Sime, Louise C. orcid:0000-0002-9093-7926 Kohfeld, Karen E.; Le Quere, Corinne; Wolff, Eric; de Boer, Agatha M.; Graham, Robert M.; Bopp, Laurent. 2013 Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison. Quaternary Science Reviews, 64. 104-120. https://doi.org/10.1016/j.quascirev.2012.12.008 <https://doi.org/10.1016/j.quascirev.2012.12.008> Publication - Article PeerReviewed 2013 ftnerc https://doi.org/10.1016/j.quascirev.2012.12.008 2023-02-04T19:31:59Z The Southern Hemisphere (SH) westerly winds are thought to be critical to global ocean circulation, productivity, and carbon storage. For example, an equatorward shift in the winds, though its affect on the Southern Ocean circulation, has been suggested as the leading cause for the reduction in atmospheric CO2 during the Last Glacial period. Despite the importance of the winds, it is currently not clear, from observations or model results, how they behave during the Last Glacial. Here, an atmospheric modelling study is performed to help determine likely changes in the SH westerly winds during the Last Glacial Maximum (LGM). Using LGM boundary conditions, the maximum in SH westerlies is strengthened by ∼+1 m s−1 and moved southward by ∼2° at the 850 hPa pressure level. Boundary layer stabilisation effects over equatorward extended LGM sea-ice can lead to a small apparent equatorward shift in the wind band at the surface. Further sensitivity analysis with individual boundary condition changes indicate that changes in sea surface temperatures are the strongest factor behind the wind change. The HadAM3 atmospheric simulations, along with published PMIP2 coupled climate model simulations, are then assessed against the newly synthesised database of moisture observations for the LGM. Although the moisture data is the most commonly cited evidence in support of a large equatorward shift in the SH winds during the LGM, none of the models that produce realistic LGM precipitation changes show such a large equatorward shift. In fact, the model which best simulates the moisture proxy data is the HadAM3 LGM simulation which shows a small poleward wind shift. While we cannot prove here that a large equatorward shift would not be able to reproduce the moisture data as well, we show that the moisture proxies do not provide an observational evidence base for it. Article in Journal/Newspaper Sea ice Southern Ocean Natural Environment Research Council: NERC Open Research Archive Southern Ocean Quaternary Science Reviews 64 104 120 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
English |
description |
The Southern Hemisphere (SH) westerly winds are thought to be critical to global ocean circulation, productivity, and carbon storage. For example, an equatorward shift in the winds, though its affect on the Southern Ocean circulation, has been suggested as the leading cause for the reduction in atmospheric CO2 during the Last Glacial period. Despite the importance of the winds, it is currently not clear, from observations or model results, how they behave during the Last Glacial. Here, an atmospheric modelling study is performed to help determine likely changes in the SH westerly winds during the Last Glacial Maximum (LGM). Using LGM boundary conditions, the maximum in SH westerlies is strengthened by ∼+1 m s−1 and moved southward by ∼2° at the 850 hPa pressure level. Boundary layer stabilisation effects over equatorward extended LGM sea-ice can lead to a small apparent equatorward shift in the wind band at the surface. Further sensitivity analysis with individual boundary condition changes indicate that changes in sea surface temperatures are the strongest factor behind the wind change. The HadAM3 atmospheric simulations, along with published PMIP2 coupled climate model simulations, are then assessed against the newly synthesised database of moisture observations for the LGM. Although the moisture data is the most commonly cited evidence in support of a large equatorward shift in the SH winds during the LGM, none of the models that produce realistic LGM precipitation changes show such a large equatorward shift. In fact, the model which best simulates the moisture proxy data is the HadAM3 LGM simulation which shows a small poleward wind shift. While we cannot prove here that a large equatorward shift would not be able to reproduce the moisture data as well, we show that the moisture proxies do not provide an observational evidence base for it. |
format |
Article in Journal/Newspaper |
author |
Sime, Louise C. Kohfeld, Karen E. Le Quere, Corinne Wolff, Eric de Boer, Agatha M. Graham, Robert M. Bopp, Laurent |
spellingShingle |
Sime, Louise C. Kohfeld, Karen E. Le Quere, Corinne Wolff, Eric de Boer, Agatha M. Graham, Robert M. Bopp, Laurent Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison |
author_facet |
Sime, Louise C. Kohfeld, Karen E. Le Quere, Corinne Wolff, Eric de Boer, Agatha M. Graham, Robert M. Bopp, Laurent |
author_sort |
Sime, Louise C. |
title |
Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison |
title_short |
Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison |
title_full |
Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison |
title_fullStr |
Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison |
title_full_unstemmed |
Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison |
title_sort |
southern hemisphere westerly wind changes during the last glacial maximum: model-data comparison |
publisher |
Elsevier |
publishDate |
2013 |
url |
http://nora.nerc.ac.uk/id/eprint/18845/ https://nora.nerc.ac.uk/id/eprint/18845/1/QSR_Sime_reduced.pdf http://www.sciencedirect.com/science/article/pii/S0277379112005215 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Sea ice Southern Ocean |
genre_facet |
Sea ice Southern Ocean |
op_relation |
https://nora.nerc.ac.uk/id/eprint/18845/1/QSR_Sime_reduced.pdf Sime, Louise C. orcid:0000-0002-9093-7926 Kohfeld, Karen E.; Le Quere, Corinne; Wolff, Eric; de Boer, Agatha M.; Graham, Robert M.; Bopp, Laurent. 2013 Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison. Quaternary Science Reviews, 64. 104-120. https://doi.org/10.1016/j.quascirev.2012.12.008 <https://doi.org/10.1016/j.quascirev.2012.12.008> |
op_doi |
https://doi.org/10.1016/j.quascirev.2012.12.008 |
container_title |
Quaternary Science Reviews |
container_volume |
64 |
container_start_page |
104 |
op_container_end_page |
120 |
_version_ |
1766195570642255872 |