Fast response of deep ocean circulation to mid-latitude winds in the Atlantic

Abstract

\textit{In situ} observations of transbasin deep ocean transports at $26^\circ$N show variability on monthly to decadal timescales (2004--2015). Satellite-based estimates of ocean bottom pressure from the Gravity Recovery and Climate Experiment (GRACE) satellites were previously used to estimate interannual variability of deep ocean transports at $26^\circ$N. Here, we use GRACE ocean bottom pressure, reanalysis winds and \textit{in situ} transport estimates at $26^\circ$N to diagnose the large-scale response of the deep ocean circulation to wind-forcing. We find that deep ocean transports -- including those associated with a reversal of the Atlantic meridional overturning circulation in 2009/10 and 2010/11 -- are part of a large-scale response to wind stress curl over the intergyre-gyre region. Wind-forcing dominates deep ocean circulation variability on monthly timescales, but interannual fluctuations in the residual \textit{in situ} transports (after removing the wind-effect) are also captured by GRACE bottom pressure measurements. On decadal timescales, uncertainty in regional trends in GRACE ocean bottom pressure preclude investigation of decadal-timescale transport trends.