Chris Meinen, Bill Johns, Silvia Garzoli, Erik van Sebille,
Darren Rayner, Torsten Kanzow, and Molly Baringer
In Deep Sea Research II, 2013, volume 85, pages 154-168.
10.1016/j.dsr2.2012.07.036
Five years of data from a line of dynamic height moorings (DHM), bottom-pressure recorders (BPR), and pressure-equipped inverted echo sounders (PIES) near the Atlantic Ocean western boundary at 26.5°N are used to evaluate the structure and variability of the Deep Western Boundary Current (DWBC) during 2004-2009. Comparisons made between transports estimated from the DHM+BPR and those made by the PIES demonstrate that the two systems are collecting equivalent volume transport information (correlation coefficient r = 0.96, root-mean-square difference = 6 Sv; 1 Sv = 106 m3 s-1). Integrated to ~450 km off from the continental shelf and between 800 and 4800 dbar, the DWBC has a mean transport of approximately 32 Sv and a standard deviation during these five years of 16 Sv. Both the barotropic (full-depth vertical mean) and baroclinic flows have significant variability (changes exceeding 10 Sv) on time scales ranging from a few days to months, with the barotropic variations being larger and more energetic at all time scales. The annual cycle of the deep transport is highly dependent on the horizontal integration distance; integrating ~100 km offshore yields an annual cycle of roughly similar magnitude but shifted in phase relative to that found from current meter arrays in the 1980s-1990s, while the annual cycle becomes quite weak when integrating ~450 km offshore. Variations in the DWBC transport far exceed those of the total basin-wide meridional overturning circulation (standard deviations of 16 Sv vs. 5 Sv). Transport integrated in the deep layer out to the west side of the Mid-Atlantic Ridge still demonstrates a surprisingly high variance, indicating that some compensation of the western basin deep variability must occur in the eastern basin.