A model study on internally generated variability in subtropical mode water formation
Internally generated variability in the subtropical gyre is studied as a possible mechanism for the observed interannual to decadal variability in subtropical mode water formation. An isopycnic ocean model with idealized geometry and forcing which mimics the North Atlantic subtropical gyre is used f...
Published in: | Journal of Geophysical Research: Oceans |
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Online Access: | https://eprints.soton.ac.uk/349192/ |
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ftsouthampton:oai:eprints.soton.ac.uk:349192 2023-07-30T04:05:30+02:00 A model study on internally generated variability in subtropical mode water formation Hazeleger, W. Drijfhout, S.S. 2000-01 https://eprints.soton.ac.uk/349192/ unknown Hazeleger, W. and Drijfhout, S.S. (2000) A model study on internally generated variability in subtropical mode water formation. Journal of Geophysical Research, 105 (C6), 13965-13979. (doi:10.1029/2000JC900041 <http://dx.doi.org/10.1029/2000JC900041>). Article PeerReviewed 2000 ftsouthampton https://doi.org/10.1029/2000JC900041 2023-07-09T21:44:43Z Internally generated variability in the subtropical gyre is studied as a possible mechanism for the observed interannual to decadal variability in subtropical mode water formation. An isopycnic ocean model with idealized geometry and forcing which mimics the North Atlantic subtropical gyre is used for this purpose. The horizontal resolution is sufficiently high and the friction and diffusion sufficiently low for the flow to become barotropically and baroclinically unstable. Two modes of low-frequency variability are found. Both modes consist of westward propagating thickness anomalies. The anomalies have a first baroclinic modal structure with a maximum amplitude at the thermocline. One mode has a timescale of 8 years and a basin wide spatial scale; the other has a timescale of 4.5 years and a smaller spatial scale. The modes appear to be damped when the diffusion is high. In that case, the 8-year mode can be excited by a spatially coherent stochastic wind stress. The evolution of the modes is determined by an interaction between the mean flow and the low-frequency variability itself. The modes are instabilities of the mean flow determined by the basic stratification. It appears that coupling to the atmosphere and a parameterization of surface mixing are necessary for the low-frequency variability to appear in the mixed layer. The coupling and surface mixing do not play a role in generating the modes. It is concluded that these internally generated modes may play a role in the observed variability in mode water formation. Article in Journal/Newspaper North Atlantic University of Southampton: e-Prints Soton Journal of Geophysical Research: Oceans 105 C6 13965 13979 |
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Open Polar |
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University of Southampton: e-Prints Soton |
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ftsouthampton |
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unknown |
description |
Internally generated variability in the subtropical gyre is studied as a possible mechanism for the observed interannual to decadal variability in subtropical mode water formation. An isopycnic ocean model with idealized geometry and forcing which mimics the North Atlantic subtropical gyre is used for this purpose. The horizontal resolution is sufficiently high and the friction and diffusion sufficiently low for the flow to become barotropically and baroclinically unstable. Two modes of low-frequency variability are found. Both modes consist of westward propagating thickness anomalies. The anomalies have a first baroclinic modal structure with a maximum amplitude at the thermocline. One mode has a timescale of 8 years and a basin wide spatial scale; the other has a timescale of 4.5 years and a smaller spatial scale. The modes appear to be damped when the diffusion is high. In that case, the 8-year mode can be excited by a spatially coherent stochastic wind stress. The evolution of the modes is determined by an interaction between the mean flow and the low-frequency variability itself. The modes are instabilities of the mean flow determined by the basic stratification. It appears that coupling to the atmosphere and a parameterization of surface mixing are necessary for the low-frequency variability to appear in the mixed layer. The coupling and surface mixing do not play a role in generating the modes. It is concluded that these internally generated modes may play a role in the observed variability in mode water formation. |
format |
Article in Journal/Newspaper |
author |
Hazeleger, W. Drijfhout, S.S. |
spellingShingle |
Hazeleger, W. Drijfhout, S.S. A model study on internally generated variability in subtropical mode water formation |
author_facet |
Hazeleger, W. Drijfhout, S.S. |
author_sort |
Hazeleger, W. |
title |
A model study on internally generated variability in subtropical mode water formation |
title_short |
A model study on internally generated variability in subtropical mode water formation |
title_full |
A model study on internally generated variability in subtropical mode water formation |
title_fullStr |
A model study on internally generated variability in subtropical mode water formation |
title_full_unstemmed |
A model study on internally generated variability in subtropical mode water formation |
title_sort |
model study on internally generated variability in subtropical mode water formation |
publishDate |
2000 |
url |
https://eprints.soton.ac.uk/349192/ |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
Hazeleger, W. and Drijfhout, S.S. (2000) A model study on internally generated variability in subtropical mode water formation. Journal of Geophysical Research, 105 (C6), 13965-13979. (doi:10.1029/2000JC900041 <http://dx.doi.org/10.1029/2000JC900041>). |
op_doi |
https://doi.org/10.1029/2000JC900041 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
105 |
container_issue |
C6 |
container_start_page |
13965 |
op_container_end_page |
13979 |
_version_ |
1772817470281744384 |