Variability of Shallow and Deep Western Boundary Currents off the Bahamas during 2004–05: Results from the 26°N RAPID–MOC Array
- 1 March 2008
- journal article
- Published by American Meteorological Society in Journal of Physical Oceanography
- Vol. 38 (3), 605-623
- https://doi.org/10.1175/2007jpo3791.1
Abstract
Data from an array of six moorings deployed east of Abaco, Bahamas, along 26.5°N during March 2004–May 2005 are analyzed. These moorings formed the western boundary array of a transbasin observing system designed to continuously monitor the meridional overturning circulation and meridional heat flux in the subtropical North Atlantic, under the framework of the joint U.K.–U.S. Rapid Climate Change (RAPID)–Meridional Overturning Circulation (MOC) Program. Important features of the western boundary circulation include the southward-flowing deep western boundary current (DWBC) below 1000 m and the northward-flowing “Antilles” Current in the upper 1000 m. Transports in the western boundary layer are estimated from direct current meter observations and from dynamic height moorings that measure the spatially integrated geostrophic flow between moorings. The results of these methods are combined to estimate the time-varying transports in the upper and deep ocean over the width of the western boundary layer to a distance of 500 km offshore of the Bahamas escarpment. The net southward transport of the DWBC across this region, inclusive of northward deep recirculation, is −26.5 Sv (Sv ≡ 106 m3 s−1), which is divided nearly equally between upper (−13.9 Sv) and lower (−12.6 Sv) North Atlantic Deep Water (NADW). In the top 1000 m, 6.0 Sv flows northward in a thermocline-intensified jet near the western boundary. These transports are found to agree well with historical current meter data in the region collected between 1986 and 1997. Variability in both shallow and deep components of the circulation is large, with transports above 1000 m varying between −15 and +25 Sv and deep transports varying between −60 and +3 Sv. Much of this transport variability, associated with barotropic fluctuations, occurs on relatively short time scales of several days to a few weeks. Upon removal of the barotropic fluctuations, slower baroclinic transport variations are revealed, including a temporary stoppage of the lower NADW transport in the DWBC during November 2004.Keywords
This publication has 26 references indexed in Scilit:
- Temporal Variability of the Atlantic Meridional Overturning Circulation at 26.5°NScience, 2007
- Deep western boundary current east of Abaco: Mean structure and transportJournal of Marine Research, 2005
- Deviation of Long-Period Tides from Equilibrium: Kinematics and GeostrophyJournal of Physical Oceanography, 2003
- Improved estimates of global ocean circulation, heat transport and mixing from hydrographic dataNature, 2000
- Meridional Heat Transport Variability at 26.5°N in the North AtlanticJournal of Physical Oceanography, 1997
- Direct observations of the current structure east of the BahamasGeophysical Research Letters, 1996
- Response of Circulation and Heat Transport in the North Atlantic to Changes in Thermohaline Forcing in Northern Latitudes: A Model StudyJournal of Physical Oceanography, 1994
- Seasonal Transport Variations in the Florida Straits: A Model StudyJournal of Physical Oceanography, 1985
- Direct estimates and mechanisms of ocean heat transportDeep Sea Research Part A. Oceanographic Research Papers, 1982
- A New Method of Interpolation and Smooth Curve Fitting Based on Local ProceduresJournal of the ACM, 1970