Observed basin-scale response of the North Atlantic Meridional Overturning Circulation to wind stress forcing

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 years. These time series are derived from four mooring arrays located on the western boundary of the North Atlantic: the RAPID WAVE array (42.5°N), the Woods Hole Oceanographic Institution Line W array (39°N), the RAPID MOC/MOCHA array (26.5°N), and the 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 drives the MOC coherently at four latitudes, on the timescales available for this study. The dominant mode of covariance is interpreted as rapid barotropic oceanic adjustments to wind stress forcing, eventually forming two counter-rotating 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 which likely interact with topography to form overturning cells.