Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models
Multidecadal variability in the Atlantic meridional overturning circulation (AMOC) of the ocean is diagnosed in the NCAR Community Climate System Model, version 3 (CCSM3), and the GFDL Coupled Model (CM2.1). Common diagnostic approaches are applied to draw out similarities and differences between th...
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ftmit:oai:dspace.mit.edu:1721.1/76732 2024-06-23T07:54:26+00:00 Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models Tulloch, Ross Marshall, John C Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Tulloch, Ross Marshall, John C. 2011-08 application/pdf http://hdl.handle.net/1721.1/76732 en_US eng American Meteorological Society http://dx.doi.org/10.1175/jcli-d-11-00460.1 Journal of Climate 0894-8755 1520-0442 http://hdl.handle.net/1721.1/76732 Tulloch, Ross, and John Marshall. “Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models.” Journal of Climate 25.12 (2012): 4067–4080. © 2012 American Meteorological Society orcid:0000-0001-9230-3591 Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. American Meteorological Society Article http://purl.org/eprint/type/JournalArticle 2011 ftmit https://doi.org/10.1175/jcli-d-11-00460.1 2024-05-29T01:02:38Z Multidecadal variability in the Atlantic meridional overturning circulation (AMOC) of the ocean is diagnosed in the NCAR Community Climate System Model, version 3 (CCSM3), and the GFDL Coupled Model (CM2.1). Common diagnostic approaches are applied to draw out similarities and differences between the two models. An index of AMOC variability is defined, and the manner in which key variables covary with it is determined. In both models the following is found. (i) AMOC variability is associated with upper-ocean (top 1 km) density anomalies (dominated by temperature) on the western margin of the basin in the region of the Mann eddy with a period of about 20 years. These anomalies modulate the trajectory and strength of the North Atlantic Current. The importance of the western margin is a direct consequence of the thermal wind relation and is independent of the mechanisms that create those density anomalies. (ii) Density anomalies in this key region are part of a larger-scale pattern that propagates around the subpolar gyre and acts as a “pacemaker” of AMOC variability. (iii) The observed variability is consistent with the primary driving mechanism being stochastic wind curl forcing, with Labrador Sea convection playing a secondary role. Also, “toy models” of delayed oscillator form are fitted to power spectra of key variables and are used to infer “quality factors” (Q-factors), which characterize the bandwidth relative to the center frequency and hence AMOC predictability horizons. The two models studied here have Q-factors of around 2, suggesting that prediction is possible out to about two cycles, which is likely larger than the real AMOC. Article in Journal/Newspaper Labrador Sea north atlantic current North Atlantic DSpace@MIT (Massachusetts Institute of Technology) Curl ENVELOPE(-63.071,-63.071,-70.797,-70.797) Journal of Climate 25 12 4067 4080 |
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Open Polar |
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DSpace@MIT (Massachusetts Institute of Technology) |
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ftmit |
language |
English |
description |
Multidecadal variability in the Atlantic meridional overturning circulation (AMOC) of the ocean is diagnosed in the NCAR Community Climate System Model, version 3 (CCSM3), and the GFDL Coupled Model (CM2.1). Common diagnostic approaches are applied to draw out similarities and differences between the two models. An index of AMOC variability is defined, and the manner in which key variables covary with it is determined. In both models the following is found. (i) AMOC variability is associated with upper-ocean (top 1 km) density anomalies (dominated by temperature) on the western margin of the basin in the region of the Mann eddy with a period of about 20 years. These anomalies modulate the trajectory and strength of the North Atlantic Current. The importance of the western margin is a direct consequence of the thermal wind relation and is independent of the mechanisms that create those density anomalies. (ii) Density anomalies in this key region are part of a larger-scale pattern that propagates around the subpolar gyre and acts as a “pacemaker” of AMOC variability. (iii) The observed variability is consistent with the primary driving mechanism being stochastic wind curl forcing, with Labrador Sea convection playing a secondary role. Also, “toy models” of delayed oscillator form are fitted to power spectra of key variables and are used to infer “quality factors” (Q-factors), which characterize the bandwidth relative to the center frequency and hence AMOC predictability horizons. The two models studied here have Q-factors of around 2, suggesting that prediction is possible out to about two cycles, which is likely larger than the real AMOC. |
author2 |
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Tulloch, Ross Marshall, John C. |
format |
Article in Journal/Newspaper |
author |
Tulloch, Ross Marshall, John C |
spellingShingle |
Tulloch, Ross Marshall, John C Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models |
author_facet |
Tulloch, Ross Marshall, John C |
author_sort |
Tulloch, Ross |
title |
Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models |
title_short |
Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models |
title_full |
Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models |
title_fullStr |
Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models |
title_full_unstemmed |
Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models |
title_sort |
exploring mechanisms of variability and predictability of atlantic meridional overturning circulation in two coupled climate models |
publisher |
American Meteorological Society |
publishDate |
2011 |
url |
http://hdl.handle.net/1721.1/76732 |
long_lat |
ENVELOPE(-63.071,-63.071,-70.797,-70.797) |
geographic |
Curl |
geographic_facet |
Curl |
genre |
Labrador Sea north atlantic current North Atlantic |
genre_facet |
Labrador Sea north atlantic current North Atlantic |
op_source |
American Meteorological Society |
op_relation |
http://dx.doi.org/10.1175/jcli-d-11-00460.1 Journal of Climate 0894-8755 1520-0442 http://hdl.handle.net/1721.1/76732 Tulloch, Ross, and John Marshall. “Exploring Mechanisms of Variability and Predictability of Atlantic Meridional Overturning Circulation in Two Coupled Climate Models.” Journal of Climate 25.12 (2012): 4067–4080. © 2012 American Meteorological Society orcid:0000-0001-9230-3591 |
op_rights |
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. |
op_doi |
https://doi.org/10.1175/jcli-d-11-00460.1 |
container_title |
Journal of Climate |
container_volume |
25 |
container_issue |
12 |
container_start_page |
4067 |
op_container_end_page |
4080 |
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1802646590733680640 |