Large near-inertial oscillations of the Atlantic meridional overturning circulation

Blaker, Adam T., Hirschi, Joël J-M., Sinha, Bablu, de Cuevas, Beverly, Alderson, Steven, Coward, Andrew and Madec, Gurvan (2012) Large near-inertial oscillations of the Atlantic meridional overturning circulation. Ocean Modelling, 42, 50-56. (doi:10.1016/j.ocemod.2011.11.008).

Abstract

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.

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