Evidence of strong inertia-gravity wave activity during the POMME experiment

Type Publication
Date 2005-06
Language English
Copyright 2005 American Geophysical Union
Author(s) Bouruet-Aubertot Pascale3, Mercier HerleORCID1, 2, Gaillard FabienneORCID2, Lherminier PascaleORCID2
Affiliation(s) 1 : CNRS, Univ Paris 06, Inst Rech Dev, UMR 7617,Inst Pierre Simon Laplace, Lab Oceanog & Climat Expt & Approches Numer, F-75252 Paris, France.
2 : Univ Bretagne Occidentale, Inst Francais Rech Exploitat Mer, CNRS,UMR 6523, Lab Phys Oceans, Plouzane, France.
3 : Univ Paris 06, Inst Rech Dev, UMR 7617,Inst Pierre Simon Laplace, Lab Oceanog & Climat Expt & Approches Numer, F-75252 Paris, France.
Source Journal of Geophysical Union - Research C - Oceans (0148-0227) (American Geophysical Union), 2005-06 , Vol. 110 , N. C7
DOI 10.1029/2004JC002747
WOS© Times Cited 9
Keyword(s) Turbulent mixing, Tnertia gravity waves
Abstract The purpose of this paper is to characterize inertia-gravity waves (IGW) activity and to investigate the variability of these waves in relationship to atmospheric forcing and larger-scale motions. To this aim, we analyzed Eulerian measurements of horizontal currents and temperature collected over 1 year during the Programme Océan Multidisciplinaire Méso Echelle (POMME). We focused on the main frequency components of the IGW spectrum, namely the inertial frequency f and the semidiurnal frequency M2. Time evolution of the relative energy of these two components gave evidence of isolated events of high intensity. We performed a detailed analysis of these events and identified mechanisms of generation of these waves. Localized spots of intense, near-inertial IGW were observed in winter. During the mixed layer deepening, one event was correlated with plume-like structures resulting from peaks of intense surface cooling. This suggests a local generation process driven by strong downward vertical motions. Instead, other events of strong IGW could be related to submesoscale features, characteristic of a frontal region, in particular, wave trapping within anticyclonic eddies. In contrast, a downward energy propagation down to about 500 m below the mixed layer was isolated after a stormy period. Eventually, internal tidal beams, possibly generated at a nearby seamount, intermittently crossed the mooring, though less energetically than the previous events. Last, we estimated the eddy diffusivity from the velocity vertical shear. Large variations were obtained, from 10-6 m2/s up to 10-3 m2/s, consistent with the intense events previously isolated.
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