Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales
It is well-established that, at periods shorter than a year, variations in Antarctic circumpolar transport are reflected in a barotropic mode, known as the southern mode , in which sea level and bottom pressure varies coherently around Antarctica. Here, we use two multidecadal ocean model runs to in...
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ftcopernicus:oai:publications.copernicus.org:os22718 2023-05-15T13:54:27+02:00 Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales Hughes, C. W. Williams, Joanne Coward, A. C. de Cuevas, B. A. 2018-01-15 application/pdf https://doi.org/10.5194/os-10-215-2014 https://os.copernicus.org/articles/10/215/2014/ eng eng doi:10.5194/os-10-215-2014 https://os.copernicus.org/articles/10/215/2014/ eISSN: 1812-0792 Text 2018 ftcopernicus https://doi.org/10.5194/os-10-215-2014 2020-07-20T16:25:08Z It is well-established that, at periods shorter than a year, variations in Antarctic circumpolar transport are reflected in a barotropic mode, known as the southern mode , in which sea level and bottom pressure varies coherently around Antarctica. Here, we use two multidecadal ocean model runs to investigate the behaviour of the southern mode at timescales on which density changes become important, leading to a baroclinic component to the adjustment. We find that the concept of a southern mode in bottom pressure remains valid, and remains a direct measure of the circumpolar transport, with changes at the northern boundary playing only a small role even on decadal timescales. However, at periods longer than about 5 years, density changes start to play a role, leading to a surface intensification of the vertical profile of the transport. We also find that barotropic currents on the continental slope account for a significant fraction of the variability, and produce surface intensification in the meridional-integral flow. Circumpolar sea level and transport are related at all investigated timescales. However, the role of density variations results in a ratio of sea level change to transport which becomes larger at longer timescales. This means that any long-term transport monitoring strategy based on present measurement systems must involve multiplying the observed quantity by a factor which depends on frequency. Text Antarc* Antarctic Antarctica Copernicus Publications: E-Journals Antarctic Ocean Science 10 2 215 225 |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
It is well-established that, at periods shorter than a year, variations in Antarctic circumpolar transport are reflected in a barotropic mode, known as the southern mode , in which sea level and bottom pressure varies coherently around Antarctica. Here, we use two multidecadal ocean model runs to investigate the behaviour of the southern mode at timescales on which density changes become important, leading to a baroclinic component to the adjustment. We find that the concept of a southern mode in bottom pressure remains valid, and remains a direct measure of the circumpolar transport, with changes at the northern boundary playing only a small role even on decadal timescales. However, at periods longer than about 5 years, density changes start to play a role, leading to a surface intensification of the vertical profile of the transport. We also find that barotropic currents on the continental slope account for a significant fraction of the variability, and produce surface intensification in the meridional-integral flow. Circumpolar sea level and transport are related at all investigated timescales. However, the role of density variations results in a ratio of sea level change to transport which becomes larger at longer timescales. This means that any long-term transport monitoring strategy based on present measurement systems must involve multiplying the observed quantity by a factor which depends on frequency. |
format |
Text |
author |
Hughes, C. W. Williams, Joanne Coward, A. C. de Cuevas, B. A. |
spellingShingle |
Hughes, C. W. Williams, Joanne Coward, A. C. de Cuevas, B. A. Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales |
author_facet |
Hughes, C. W. Williams, Joanne Coward, A. C. de Cuevas, B. A. |
author_sort |
Hughes, C. W. |
title |
Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales |
title_short |
Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales |
title_full |
Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales |
title_fullStr |
Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales |
title_full_unstemmed |
Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales |
title_sort |
antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales |
publishDate |
2018 |
url |
https://doi.org/10.5194/os-10-215-2014 https://os.copernicus.org/articles/10/215/2014/ |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_source |
eISSN: 1812-0792 |
op_relation |
doi:10.5194/os-10-215-2014 https://os.copernicus.org/articles/10/215/2014/ |
op_doi |
https://doi.org/10.5194/os-10-215-2014 |
container_title |
Ocean Science |
container_volume |
10 |
container_issue |
2 |
container_start_page |
215 |
op_container_end_page |
225 |
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1766260367875375104 |