Large near-inertial oscillations of the Atlantic meridional overturning circulation

The Atlantic meridional overturning circulation (AMOC) is a key contributor to Europe’s mild climate. Both observations and models suggest that the AMOC strength varies on a wide range of timescales. Here we show the existence of previously unreported large near inertial AMOC oscillations in a high resolution ocean model. Peak-to-peak these oscillations can exceed 50 Sv (50 · 106 m3 s−1) in one day. The AMOC oscillations are caused by equatorward propagating near-inertial gravity waves (NIGWs) which are forced by temporally changing wind forcing. The existence of NIGWs in the ocean is supported by observations, and a significant fraction of the ocean’s kinetic energy is associated with the near inertial frequencies. Our results also suggest that the NIGW-driven MOC variability would be near invisible to contemporary AMOC observing systems such as the RAPID MOC system at 26.5°N.

► We analyse the Atlantic meridional overturning circulation (AMOC) in an ocean model. ► We find high frequency variability which can exceed 50 Sv (peak-to-peak) in 24 h. ► The large variability is caused by near inertial gravity waves (NIGWs). ► The NIGWs and corresponding AMOC variability are driven by wind variability. ► The variability would be near invisible to comtemporary AMOC observing systems.