Enhanced Abyssal Mixing in the Equatorial Pacific Associated with Non-Traditional Effects

Type Article
Date 2021-06
Language English
Author(s) Delorme Bertrand L.1, Thomas Leif N1, Marchesiello Patrick2, Gula Jonathan3, 4, Roullet Guillaume3, Molemaker M. Jeroen5
Affiliation(s) 1 : Earth System Science Department, Stanford University, Stanford, California
2 : IRD/LEGOS, Toulouse, France
3 : Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Océanographie Physique et Spatiale (LOPS), IUEM, Brest, France
4 : Institut Universitaire de France (IUF), France
5 : Department of Atmospheric and Oceanic Sciences, University of California Los Angeles, Los Angeles, California
Source Journal Of Physical Oceanography (0022-3670) (American Meteorological Society), 2021-06 , Vol. 51 , N. 6 , P. 1892-1914
DOI 10.1175/JPO-D-20-0238.1
WOS© Times Cited 4
Keyword(s) Tropics, Abyssal circulation, Diapycnal mixing, Waves, oceanic

Recent theoretical work has shown that, when the so-called nontraditional effects are taken into account, the reflection of equatorially trapped waves (ETWs) off the seafloor generates strong vertical shear that results in bottom-intensified mixing at the inertial latitude of the ETW via a mechanism of critical reflection. It has been estimated that this process could play an important role in driving diapycnal upwelling in the abyssal meridional overturning circulation (AMOC). However, these results were derived under an idealized configuration with a monochromatic ETW propagating through a flat ocean at rest. To test the theory in a flow that is more representative of the ocean, we contrast a set of realistic numerical simulations of the eastern equatorial Pacific run using either the hydrostatic or quasi-hydrostatic approximation, the latter of which accounts for nontraditional effects. The simulations are nested into a Pacific-wide hydrostatic parent solution forced with climatological data and realistic bathymetry, resulting in an ETW field and a deep circulation consistent with observations. Using these simulations, we observe enhanced abyssal mixing in the quasi-hydrostatic run, even over smooth topography, that is absent in the hydrostatic run. The mixing is associated with inertial shear that has spatiotemporal properties consistent with the critical reflection mechanism. The enhanced mixing results in a weakening of the abyssal stratification and drives diapycnal upwelling in our simulation, in agreement with the predictions from the idealized simulations. The diapycnal upwelling is O(10) Sv (1 Sv ≡ 106 m3 s−1) and thus could play an important role in closing the AMOC.

Full Text
File Pages Size Access
Publisher's official version 20 7 MB Open access
Top of the page

How to cite 

Delorme Bertrand L., Thomas Leif N, Marchesiello Patrick, Gula Jonathan, Roullet Guillaume, Molemaker M. Jeroen (2021). Enhanced Abyssal Mixing in the Equatorial Pacific Associated with Non-Traditional Effects. Journal Of Physical Oceanography, 51(6), 1892-1914. Publisher's official version : https://doi.org/10.1175/JPO-D-20-0238.1 , Open Access version : https://archimer.ifremer.fr/doc/00696/80797/