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Subantarctic Mode Water variability influenced by mesoscale eddies south of Tasmania

Subantarctic Mode Water variability influenced by mesoscale eddies south of Tasmania
Subantarctic Mode Water variability influenced by mesoscale eddies south of Tasmania
[1] Subantarctic Mode Water (SAMW) is formed by deep mixing on the equatorward side of the Antarctic Circumpolar Current. The subduction and export of SAMW from the Southern Ocean play an important role in global heat, freshwater, carbon, and nutrient budgets. However, the formation process and variability of SAMW remain poorly understood, largely because of a lack of observations. To determine the temporal variability of SAMW in the Australian sector of the Southern Ocean, we used a 15 year time series of repeat expendable bathythermograph sections from 1993 to 2007, seven repeat conductivity-temperature-depth sections from 1991 to 2001, and sea surface height maps. The mean temperature of the SAMW lies between 8.5°C and 9.5°C (mean of 8.8°C, standard deviation of 0.3°C), and there is no evidence of a trend over the 18 year record. However, the temperature, salinity, and pycnostad strength of the SAMW can change abruptly from section to section. In addition, the SAMW pool on a single section often consists of two or more modes with distinct temperature, salinity, and vertical homogeneity characteristics but similar density. We show that the multiple types of mode water can be explained by the advection of anomalous water from eddies and meanders of the fronts bounding the Subantarctic Zone and by recirculation of SAMW of different ages. Our results suggest that infrequently repeated sections can potentially produce misleading results because of aliasing of high interannual variability.
Subantarctic Mode Water, Subantarctic Front, mesoscale features, water mass variability, Southern Ocean
2169-9275
C04004
Herraiz-Borreguero, Laura
faa962ba-19f8-4cf3-83be-ee4972fdbe9f
Rintoul, Stephen R.
ff078a21-d6cd-45bf-8c8f-f81f2e8ae410
Herraiz-Borreguero, Laura
faa962ba-19f8-4cf3-83be-ee4972fdbe9f
Rintoul, Stephen R.
ff078a21-d6cd-45bf-8c8f-f81f2e8ae410

Herraiz-Borreguero, Laura and Rintoul, Stephen R. (2010) Subantarctic Mode Water variability influenced by mesoscale eddies south of Tasmania. Journal of Geophysical Research: Oceans, 115 (C4), C04004. (doi:10.1029/2008JC005146).

Record type: Article

Abstract

[1] Subantarctic Mode Water (SAMW) is formed by deep mixing on the equatorward side of the Antarctic Circumpolar Current. The subduction and export of SAMW from the Southern Ocean play an important role in global heat, freshwater, carbon, and nutrient budgets. However, the formation process and variability of SAMW remain poorly understood, largely because of a lack of observations. To determine the temporal variability of SAMW in the Australian sector of the Southern Ocean, we used a 15 year time series of repeat expendable bathythermograph sections from 1993 to 2007, seven repeat conductivity-temperature-depth sections from 1991 to 2001, and sea surface height maps. The mean temperature of the SAMW lies between 8.5°C and 9.5°C (mean of 8.8°C, standard deviation of 0.3°C), and there is no evidence of a trend over the 18 year record. However, the temperature, salinity, and pycnostad strength of the SAMW can change abruptly from section to section. In addition, the SAMW pool on a single section often consists of two or more modes with distinct temperature, salinity, and vertical homogeneity characteristics but similar density. We show that the multiple types of mode water can be explained by the advection of anomalous water from eddies and meanders of the fronts bounding the Subantarctic Zone and by recirculation of SAMW of different ages. Our results suggest that infrequently repeated sections can potentially produce misleading results because of aliasing of high interannual variability.

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More information

Published date: April 2010
Keywords: Subantarctic Mode Water, Subantarctic Front, mesoscale features, water mass variability, Southern Ocean
Organisations: Physical Oceanography

Identifiers

Local EPrints ID: 398745
URI: http://eprints.soton.ac.uk/id/eprint/398745
ISSN: 2169-9275
PURE UUID: a8d1c4ba-32cb-4e30-bb92-6fb0d257c7a6

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Date deposited: 01 Aug 2016 09:02
Last modified: 15 Mar 2024 01:40

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Contributors

Author: Laura Herraiz-Borreguero
Author: Stephen R. Rintoul

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