588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM
Using the GFDL coupled atmosphere–ocean general circulation model CM2.1, the transient amplification of thermohaline circulation (THC) anomalies due to its nonnormal dynamics is studied. A reduced space based on empirical orthogonal functions (EOFs) of temperature and salinity anomaly fields in the...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.419.6507 2023-05-15T17:30:49+02:00 588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM Eli Tziperman Laure Zanna Cecile Penland The Pennsylvania State University CiteSeerX Archives 2007 application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.6507 http://www.seas.harvard.edu/climate/eli/reprints/Tziperman-Zanna-Penland-2008.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.6507 http://www.seas.harvard.edu/climate/eli/reprints/Tziperman-Zanna-Penland-2008.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://www.seas.harvard.edu/climate/eli/reprints/Tziperman-Zanna-Penland-2008.pdf text 2007 ftciteseerx 2016-01-08T03:53:34Z Using the GFDL coupled atmosphere–ocean general circulation model CM2.1, the transient amplification of thermohaline circulation (THC) anomalies due to its nonnormal dynamics is studied. A reduced space based on empirical orthogonal functions (EOFs) of temperature and salinity anomaly fields in the North Atlantic is constructed. Under the assumption that the dynamics of this reduced space is linear, the propagator of the system is then evaluated and the transient growth of THC anomalies analyzed. Although the linear dynamics are stable, such that any initial perturbation eventually decays, nonnormal effects are found to result in a significant transient growth of temperature, salinity, and THC anomalies. The growth time scale for these anomalies is between 5 and 10 yr, providing an estimate of the predictability time of the North Atlantic THC in this model. There are indications that these results are merely a lower bound on the nonnormality of THC dynamics in the present coupled GCM. This seems to suggest that such nonnormal effects should be seriously considered if the predictability of the THC is to be quantitatively evaluated from models or observations. The methodology presented here may be used to produce initial perturbations to the ocean state that may result in a stricter estimate of ocean and THC predictability than the common procedure of initializing with an identical ocean state and a perturbed atmosphere. 1. Text North Atlantic Unknown |
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ftciteseerx |
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English |
description |
Using the GFDL coupled atmosphere–ocean general circulation model CM2.1, the transient amplification of thermohaline circulation (THC) anomalies due to its nonnormal dynamics is studied. A reduced space based on empirical orthogonal functions (EOFs) of temperature and salinity anomaly fields in the North Atlantic is constructed. Under the assumption that the dynamics of this reduced space is linear, the propagator of the system is then evaluated and the transient growth of THC anomalies analyzed. Although the linear dynamics are stable, such that any initial perturbation eventually decays, nonnormal effects are found to result in a significant transient growth of temperature, salinity, and THC anomalies. The growth time scale for these anomalies is between 5 and 10 yr, providing an estimate of the predictability time of the North Atlantic THC in this model. There are indications that these results are merely a lower bound on the nonnormality of THC dynamics in the present coupled GCM. This seems to suggest that such nonnormal effects should be seriously considered if the predictability of the THC is to be quantitatively evaluated from models or observations. The methodology presented here may be used to produce initial perturbations to the ocean state that may result in a stricter estimate of ocean and THC predictability than the common procedure of initializing with an identical ocean state and a perturbed atmosphere. 1. |
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The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
Eli Tziperman Laure Zanna Cecile Penland |
spellingShingle |
Eli Tziperman Laure Zanna Cecile Penland 588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM |
author_facet |
Eli Tziperman Laure Zanna Cecile Penland |
author_sort |
Eli Tziperman |
title |
588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM |
title_short |
588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM |
title_full |
588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM |
title_fullStr |
588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM |
title_full_unstemmed |
588 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 38 Nonnormal Thermohaline Circulation Dynamics in a Coupled Ocean–Atmosphere GCM |
title_sort |
588 journal of physical oceanography volume 38 nonnormal thermohaline circulation dynamics in a coupled ocean–atmosphere gcm |
publishDate |
2007 |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.6507 http://www.seas.harvard.edu/climate/eli/reprints/Tziperman-Zanna-Penland-2008.pdf |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
http://www.seas.harvard.edu/climate/eli/reprints/Tziperman-Zanna-Penland-2008.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.6507 http://www.seas.harvard.edu/climate/eli/reprints/Tziperman-Zanna-Penland-2008.pdf |
op_rights |
Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
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1766127918789951488 |