Journal
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
Volume 118, Issue 12, Pages 6461-6478Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2013JC009228
Keywords
meridional overturning circulation; transport; South Atlantic; inverted echo sounder; bottom pressure
Categories
Funding
- Institut National des Sciences de l'Univers (INSU)
- IFREMER programme Circulation Oceanique
- French Polar Institut Paul-Emile Victor (IPEV)
- Agence Nationale de la Recherche (ANR)
- Inter-American Institute for Global Change Research [CRN3070]
- US National Science Foundation [GEO-1128040]
- Sao Paulo Research Foundation (FAPESP) [2011/50552-4, 2010/06147-5]
- Cooperative Institute for Marine and Atmospheric Studies (CIMAS)
- Cooperative Institute of the University of Miami
- National Oceanic and Atmospheric Administration (NOAA) [NA10OAR4320143]
- NOAA Atlantic Oceanographic and Meteorological Laboratory
- NOAA Climate Program Office
- Directorate For Geosciences [1138881] Funding Source: National Science Foundation
- Directorate For Geosciences
- ICER [1128040] Funding Source: National Science Foundation
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Data from two boundary arrays deployed along 34.5 degrees S are combined to produce the first continuous in situ time series observations of the basin-wide meridional overturning circulation (MOC) in the South Atlantic. Daily estimates of the MOC between March 2009 and December 2010 range between 3 Sv and 39 Sv (1 Sv=10(6) m(3) s(-1)) after a 10 day low-pass filter is applied. Much of the variability in this approximate to 20 month record occurs at periods shorter than 100 days. Approximately two-thirds of the MOC variability is due to changes in the geostrophic (baroclinic plus barotropic) volume transport, with the remainder associated with the direct wind-forced Ekman transport. When low-pass filtered to match previously published analyses in the North Atlantic, the observed temporal standard deviation at 34.5 degrees S matches or somewhat exceeds that observed by time series observations at 16 degrees N, 26.5 degrees N, and 41 degrees N. For periods shorter than 20 days the basin-wide MOC variations are most strongly influenced by Ekman flows, while at periods between 20 and 90 days the geostrophic flows tend to exert slightly more control over the total transport variability of the MOC. The geostrophic shear variations are roughly equally controlled by density variations on the western and eastern boundaries at all time scales captured in the record. The observed time-mean MOC vertical structure and temporal variability agree well with the limited independent observations available for confirmation.
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