HR: 15:45h
AN: OS43A-08    [Abstracts]
TI: Variability of the Atlantic meridional overturning circulation during 2004-2005 as observed from the 26°N RAPID-MOC Array
AU: * Johns, W
EM: bjohns@rsmas.miami.edu
AF: Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL , United States
AU: Cunningham, S
EM: scu@noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, United Kingdom
AU: Kanzow, T
EM: tok@mercury.noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, United Kingdom
AU: Bryden, H
EM: hlb@mercury.noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, United Kingdom
AU: Marotzke, J
EM: marotzke@dkrz.de
AF: Max Planck Institut, Hamburg, Germany
AU: Baringer, M
EM: molly.baringer@noaa.gov
AF: NOAA Atlantic Oceanographic and Meteorological Laboratories, Miami, FL , United States
AU: Beal, L
EM: lbeal@rsmas.miami.edu
AF: Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL , United States
AU: Meinen, C
EM: christopher.meinen@noaa.gov
AF: NOAA Atlantic Oceanographic and Meteorological Laboratories, Miami, FL , United States
AU: Hirschi, J
EM: jjmh@noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, United Kingdom
AU: Rayner, D
EM: dr400@soc.soton.ac.uk
AF: National Oceanography Centre, Southampton, United Kingdom
AB: The Atlantic Meridional Overturning Circulation (MOC) strength and variability are estimated from the first year of the joint U.K./U.S. RAPID-MOC Array across 26°N in the Atlantic. The overall measurement strategy relies on deep water endpoint "dynamic height" moorings on either side of the basin to monitor the basin-wide geostrophic shear, combined with observations from clusters of moorings up the western (Bahamas) and eastern (African) continental margins, and direct measurements of the flow through the Straits of Florida by electromagnetic cable. Ekman transports derived from satellite winds are then combined with the geostrophic and direct current observations and an overall mass conservation constraint to continuously estimate the basin- wide MOC strength and vertical structure. Precision bottom pressure gauges were also employed to monitor absolute transports including barotropic circulation. The annual mean strength and standard deviation of the MOC for the period from March 2004 to March 2005 was 18.1±5.1 Sv, with instantaneous (daily) values varying over a range from nearly 10-30 Sv. The Florida Current, Ekman, and mid-ocean geostrophic transport are found to contribute about equally to the variability in the upper ocean limb of the MOC. Independent estimates of the five main contributions to net mass transport across the section (Florida Current, Bahamas western boundary, interior ocean geostrophic internal and external components, and Ekman transport) show a near balance on time scales longer than 20 days, indicating the system is working and is producing reliable estimates of the MOC. The large range of instantaneous values for the MOC strength in this one year of observations suggests that MOC estimates derived from one-time hydrographic sections are likely to be seriously aliased by short-term variability. Although the short-term variability of the MOC is large, the standard error in this one-year estimate derived from the autocorrelation statistics of the time series is approximately 1.5 Sv. Thus the array should be capable of resolving interannual variability or trends of the order of a few Sverdrups.
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4262 Ocean observing systems
DE: 4512 Currents
DE: 4532 General circulation (1218, 1222)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly