Abstract
Abstract The response of the North Atlantic meridional overturning circulation (MOC) to wind stress forcing is investigated from an observational standpoint, using four time series of overturning transports below and relative to 1000 m, overlapping by 3.6 yr. These time series are derived from four mooring arrays located on the western boundary of the North Atlantic: the RAPID Western Atlantic Variability Experiment (WAVE) array (42.5°N), the Woods Hole Oceanographic Institution Line W array (39°N), RAPID–MOC/MOCHA (26.5°N), and the Meridional Overturning Variability Experiment (MOVE) array (16°N). Using modal decompositions of the analytic cross-correlation between transports and wind stress, the basin-scale wind stress is shown to significantly drive the MOC coherently at four latitudes, on the time scales available for this study. The dominant mode of covariance is interpreted as rapid barotropic oceanic adjustments to wind stress forcing, eventually forming two counterrotating Ekman overturning cells centered on the tropics and subtropical gyre. A second mode of covariance appears related to patterns of wind stress and wind stress curl associated with the North Atlantic Oscillation, spinning anomalous horizontal circulations that likely interact with topography to form overturning cells.
Highlights
The Atlantic meridional overturning circulation (MOC) is the primary driver of poleward heat transport by the ocean
We conduct cross-spectral analyses with the new time series TM to find that it exhibits significant coherence at the 95% confidence level with T26 and TW only in a few marginal frequency bands corresponding to periods longer than 2 months
The amount of variance explained by ASVD2 is the strongest for the two northern latitudes, which is consistent with expectations of North Atlantic Oscillation (NAO)-type atmospheric patterns affecting regions outside of the tropics on interannual time scales
Summary
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida. National Oceanography Centre, and Liverpool University, Liverpool, United Kingdom. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California (Manuscript received 6 September 2016, in final form 19 November 2016)
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