Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3
This study investigates the impact of CO2 on the amplitude, frequency, and mechanisms of Atlantic meridional overturning circulation (AMOC) variability in millennial simulations of the HadCM3 coupled climate model. Multichannel singular spectrum analysis (MSSA) and empirical orthogonal functions (EO...
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American Meteorological Society
2017
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ftunivreading:oai:centaur.reading.ac.uk:73032 2024-06-23T07:50:15+00:00 Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3 Armstrong, Edward Valdes, Paul House, Jo Singarayer, Joy 2017-10 text https://centaur.reading.ac.uk/73032/ https://centaur.reading.ac.uk/73032/1/jcli-d-16-0767.1.pdf en eng American Meteorological Society https://centaur.reading.ac.uk/73032/1/jcli-d-16-0767.1.pdf Armstrong, E., Valdes, P., House, J. and Singarayer, J. <https://centaur.reading.ac.uk/view/creators/90005422.html> (2017) Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3. Journal of Climate, 30 (19). pp. 7863-7883. ISSN 1520-0442 doi: https://doi.org/10.1175/jcli-d-16-0767.1 <https://doi.org/10.1175/jcli-d-16-0767.1> cc_by_4 Article PeerReviewed 2017 ftunivreading https://doi.org/10.1175/jcli-d-16-0767.1 2024-06-11T15:06:49Z This study investigates the impact of CO2 on the amplitude, frequency, and mechanisms of Atlantic meridional overturning circulation (AMOC) variability in millennial simulations of the HadCM3 coupled climate model. Multichannel singular spectrum analysis (MSSA) and empirical orthogonal functions (EOFs) are applied to the AMOC at four quasi-equilibrium CO2 forcings. The amount of variance explained by the first and second eigenmodes appears to be small (i.e., 11.19%); however, the results indicate that both AMOC strength and variability weaken at higher CO2 concentrations. This accompanies an apparent shift from a predominant 100–125-yr cycle at 350 ppm to 160 yr at 1400 ppm. Changes in amplitude are shown to feed back onto the atmosphere. Variability may be linked to salinity-driven density changes in the Greenland–Iceland– Norwegian Seas, fueled by advection of anomalies predominantly from the Arctic and Caribbean regions. A positive density anomaly accompanies a decrease in stratification and an increase in convection and Ekman pumping, generating a strong phase of the AMOC (and vice versa). Arctic anomalies may be generated via an internal ocean mode that may be key in driving variability and are shown to weaken at higher CO2, possibly driving the overall reduction in amplitude. Tropical anomalies may play a secondary role in modulating variability and are thought to be more influential at higher CO2, possibly due to an increased residence time in the subtropical gyre and/or increased surface runoff driven by simulated dieback of the Amazon rain forest. These results indicate that CO2 may not only weaken AMOC strength but also alter the mechanisms that drive variability, both of which have implications for climate change on multicentury time scales. Article in Journal/Newspaper Arctic Climate change Greenland Iceland CentAUR: Central Archive at the University of Reading Arctic Greenland Journal of Climate 30 19 7863 7883 |
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Open Polar |
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CentAUR: Central Archive at the University of Reading |
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ftunivreading |
language |
English |
description |
This study investigates the impact of CO2 on the amplitude, frequency, and mechanisms of Atlantic meridional overturning circulation (AMOC) variability in millennial simulations of the HadCM3 coupled climate model. Multichannel singular spectrum analysis (MSSA) and empirical orthogonal functions (EOFs) are applied to the AMOC at four quasi-equilibrium CO2 forcings. The amount of variance explained by the first and second eigenmodes appears to be small (i.e., 11.19%); however, the results indicate that both AMOC strength and variability weaken at higher CO2 concentrations. This accompanies an apparent shift from a predominant 100–125-yr cycle at 350 ppm to 160 yr at 1400 ppm. Changes in amplitude are shown to feed back onto the atmosphere. Variability may be linked to salinity-driven density changes in the Greenland–Iceland– Norwegian Seas, fueled by advection of anomalies predominantly from the Arctic and Caribbean regions. A positive density anomaly accompanies a decrease in stratification and an increase in convection and Ekman pumping, generating a strong phase of the AMOC (and vice versa). Arctic anomalies may be generated via an internal ocean mode that may be key in driving variability and are shown to weaken at higher CO2, possibly driving the overall reduction in amplitude. Tropical anomalies may play a secondary role in modulating variability and are thought to be more influential at higher CO2, possibly due to an increased residence time in the subtropical gyre and/or increased surface runoff driven by simulated dieback of the Amazon rain forest. These results indicate that CO2 may not only weaken AMOC strength but also alter the mechanisms that drive variability, both of which have implications for climate change on multicentury time scales. |
format |
Article in Journal/Newspaper |
author |
Armstrong, Edward Valdes, Paul House, Jo Singarayer, Joy |
spellingShingle |
Armstrong, Edward Valdes, Paul House, Jo Singarayer, Joy Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3 |
author_facet |
Armstrong, Edward Valdes, Paul House, Jo Singarayer, Joy |
author_sort |
Armstrong, Edward |
title |
Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3 |
title_short |
Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3 |
title_full |
Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3 |
title_fullStr |
Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3 |
title_full_unstemmed |
Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3 |
title_sort |
investigating the impact of co2 on low-frequency variability of the amoc in hadcm3 |
publisher |
American Meteorological Society |
publishDate |
2017 |
url |
https://centaur.reading.ac.uk/73032/ https://centaur.reading.ac.uk/73032/1/jcli-d-16-0767.1.pdf |
geographic |
Arctic Greenland |
geographic_facet |
Arctic Greenland |
genre |
Arctic Climate change Greenland Iceland |
genre_facet |
Arctic Climate change Greenland Iceland |
op_relation |
https://centaur.reading.ac.uk/73032/1/jcli-d-16-0767.1.pdf Armstrong, E., Valdes, P., House, J. and Singarayer, J. <https://centaur.reading.ac.uk/view/creators/90005422.html> (2017) Investigating the impact of CO2 on low-frequency variability of the AMOC in HadCM3. Journal of Climate, 30 (19). pp. 7863-7883. ISSN 1520-0442 doi: https://doi.org/10.1175/jcli-d-16-0767.1 <https://doi.org/10.1175/jcli-d-16-0767.1> |
op_rights |
cc_by_4 |
op_doi |
https://doi.org/10.1175/jcli-d-16-0767.1 |
container_title |
Journal of Climate |
container_volume |
30 |
container_issue |
19 |
container_start_page |
7863 |
op_container_end_page |
7883 |
_version_ |
1802641119073271808 |