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Antarctic Circumpolar Transport and the Southern Mode: a Model Investigation of Interannual to Decadal Timescales : Volume 10, Issue 2 (10/04/2014)

By Hughes, C. W.

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Book Id: WPLBN0004020184
Format Type: PDF Article :
File Size: Pages 11
Reproduction Date: 2015

Title: Antarctic Circumpolar Transport and the Southern Mode: a Model Investigation of Interannual to Decadal Timescales : Volume 10, Issue 2 (10/04/2014)  
Author: Hughes, C. W.
Volume: Vol. 10, Issue 2
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Williams, J., De Cuevas, B. A., Coward, A. C., & Hughes, C. W. (2014). Antarctic Circumpolar Transport and the Southern Mode: a Model Investigation of Interannual to Decadal Timescales : Volume 10, Issue 2 (10/04/2014). Retrieved from

Description: School of Environmental Sciences, University of Liverpool, Liverpool, UK. 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.

Antarctic circumpolar transport and the southern mode: a model investigation of interannual to decadal timescales

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