Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current
The Southern Ocean’s Antarctic Circumpolar Current (ACC) naturally lends itself to interpretations using a zonally averaged framework. Yet, navigation around steep and complicated bathymetric obstacles suggests that local dynamics may be far removed from those described by zonally symmetric models....
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American Meteorological Society
2012
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ftnerc:oai:nora.nerc.ac.uk:19078 2023-05-15T13:45:12+02:00 Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current Thompson, Andrew F. Sallee, Jean-Baptiste 2012 text http://nora.nerc.ac.uk/id/eprint/19078/ https://nora.nerc.ac.uk/id/eprint/19078/1/JPO-D-11-0135.pdf http://journals.ametsoc.org/doi/pdf/10.1175/JPO-D-11-0135.1 en eng American Meteorological Society https://nora.nerc.ac.uk/id/eprint/19078/1/JPO-D-11-0135.pdf Thompson, Andrew F.; Sallee, Jean-Baptiste. 2012 Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current. Journal of Physical Oceanography, 42. 956-972. https://doi.org/10.1175/JPO-D-11-0135.1 <https://doi.org/10.1175/JPO-D-11-0135.1> Publication - Article PeerReviewed 2012 ftnerc https://doi.org/10.1175/JPO-D-11-0135.1 2023-02-04T19:32:08Z The Southern Ocean’s Antarctic Circumpolar Current (ACC) naturally lends itself to interpretations using a zonally averaged framework. Yet, navigation around steep and complicated bathymetric obstacles suggests that local dynamics may be far removed from those described by zonally symmetric models. In this study, both observational and numerical results indicate that zonal asymmetries, in the form of topography, impact global flow structure and transport properties. The conclusions are based on a suite of more than 1.5 million virtual drifter trajectories advected using a satellite altimetry–derived surface velocity field spanning 17 years. The focus is on sites of ‘‘cross front’’ transport as defined by movement across selected sea surface height contours that correspond to jets along most of the ACC. Cross-front exchange is localized in the lee of bathymetric features with more than 75% of crossing events occurring in regions corresponding to only 20% of the ACC’s zonal extent. These observations motivate a series of numerical experiments using a two-layer quasigeostrophic model with simple, zonally asymmetric topography, which often produces transitions in the front structure along the channel. Significantly, regimes occur where the equilibrated number of coherent jets is a function of longitude and transport barriers are not periodic. Jet reorganization is carried out by eddy flux divergences acting to both accelerate and decelerate the mean flow of the jets. Eddy kinetic energy is amplified downstream of topography due to increased baroclinicity related to topographic steering. The combination of high eddy kinetic energy and recirculation features enhances particle exchange. These results stress the complications in developing consistent circumpolar definitions of the ACC fronts. Article in Journal/Newspaper Antarc* Antarctic Natural Environment Research Council: NERC Open Research Archive Antarctic The Antarctic Journal of Physical Oceanography 42 6 956 972 |
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Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
English |
description |
The Southern Ocean’s Antarctic Circumpolar Current (ACC) naturally lends itself to interpretations using a zonally averaged framework. Yet, navigation around steep and complicated bathymetric obstacles suggests that local dynamics may be far removed from those described by zonally symmetric models. In this study, both observational and numerical results indicate that zonal asymmetries, in the form of topography, impact global flow structure and transport properties. The conclusions are based on a suite of more than 1.5 million virtual drifter trajectories advected using a satellite altimetry–derived surface velocity field spanning 17 years. The focus is on sites of ‘‘cross front’’ transport as defined by movement across selected sea surface height contours that correspond to jets along most of the ACC. Cross-front exchange is localized in the lee of bathymetric features with more than 75% of crossing events occurring in regions corresponding to only 20% of the ACC’s zonal extent. These observations motivate a series of numerical experiments using a two-layer quasigeostrophic model with simple, zonally asymmetric topography, which often produces transitions in the front structure along the channel. Significantly, regimes occur where the equilibrated number of coherent jets is a function of longitude and transport barriers are not periodic. Jet reorganization is carried out by eddy flux divergences acting to both accelerate and decelerate the mean flow of the jets. Eddy kinetic energy is amplified downstream of topography due to increased baroclinicity related to topographic steering. The combination of high eddy kinetic energy and recirculation features enhances particle exchange. These results stress the complications in developing consistent circumpolar definitions of the ACC fronts. |
format |
Article in Journal/Newspaper |
author |
Thompson, Andrew F. Sallee, Jean-Baptiste |
spellingShingle |
Thompson, Andrew F. Sallee, Jean-Baptiste Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current |
author_facet |
Thompson, Andrew F. Sallee, Jean-Baptiste |
author_sort |
Thompson, Andrew F. |
title |
Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current |
title_short |
Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current |
title_full |
Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current |
title_fullStr |
Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current |
title_full_unstemmed |
Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current |
title_sort |
jets and topography: jet transitions and the impact on transport in the antarctic circumpolar current |
publisher |
American Meteorological Society |
publishDate |
2012 |
url |
http://nora.nerc.ac.uk/id/eprint/19078/ https://nora.nerc.ac.uk/id/eprint/19078/1/JPO-D-11-0135.pdf http://journals.ametsoc.org/doi/pdf/10.1175/JPO-D-11-0135.1 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
https://nora.nerc.ac.uk/id/eprint/19078/1/JPO-D-11-0135.pdf Thompson, Andrew F.; Sallee, Jean-Baptiste. 2012 Jets and topography: jet transitions and the impact on transport in the Antarctic Circumpolar Current. Journal of Physical Oceanography, 42. 956-972. https://doi.org/10.1175/JPO-D-11-0135.1 <https://doi.org/10.1175/JPO-D-11-0135.1> |
op_doi |
https://doi.org/10.1175/JPO-D-11-0135.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
42 |
container_issue |
6 |
container_start_page |
956 |
op_container_end_page |
972 |
_version_ |
1766216785976098816 |