Transport and variability of the antarctic circumpolar current South of Africa

Type Article
Date 2008-09
Language English
Author(s) Swart S1, Speich Sabrina4, 5, Ansorge I1, Goni G3, Gladyshev S2, Lutjeharms J1
Affiliation(s) 1 : Univ Cape Town, Dept Oceanog, ZA-7701 Rondebosch, South Africa.
2 : Russian Acad Sci, Shirshov Inst Oceanol, Moscow, Russia.
3 : NOAA, Atlantic Oceanog & Meteorol Lab, Phys Oceanog Div, Miami, FL 33149 USA.
4 : Univ Bretagne Occidentale, IFREMER, Lab Phys Ocean, Brest, France.
Source Journal of Geophysical Research (0148-0227) (American Geophysical Union), 2008-09 , Vol. 113 , N. C09014 , P. NIL_45-NIL_68
DOI 10.1029/2007JC004223
WOS© Times Cited 40
Keyword(s) satellite altimetry, Antarctic Circumpolar Current, Baroclinic transport
Abstract Data from five CTD and 18 XBT sections are used to estimate the baroclinic transport ( referenced to 2500 dbar) of the ACC south of Africa. Surface dynamic height is derived from XBT data by establishing an empirical relationship between vertically integrated temperature and surface dynamic height calculated from CTD data. This temperature-derived dynamic height data compare closely with dynamic heights calculated from CTD data ( average RMS difference = 0.05 dyn m). A second empirical relationship between surface dynamic height and cumulative baroclinic transport is defined, allowing us to study a more extensive time series of baroclinic transport derived from upper ocean temperature sections. From 18 XBT transects of the ACC, the average baroclinic transport, relative to 2500 dbar, is estimated at 90 +/- 2.4 Sv. This estimate is comparable to baroclinic transport values calculated from CTD data. We then extend the baroclinic transport time-series by applying an empirical relationship between dynamic height and cumulative baroclinic transport to weekly maps of absolute dynamic topography derived from satellite altimetry, between 14 October 1992 and 23 May 2007. The estimated mean baroclinic transport of the ACC, obtained this way, is 84.7 +/- 3.0 Sv. These transports agree well with simultaneous in-situ estimates ( RMS difference in net transport = 5.2 Sv). This suggests that sea level anomalies largely reflect baroclinic transport changes above 2500 dbar.
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