Publication

2005-06

English

http://archimer.ifremer.fr/doc/2005/publication-359.pdf (1.94 Mo)

2005 American Geophysical Union

Bouruet-Aubertot Pascale³, Mercier Herle^{1, 2}, Gaillard Fabienne², Lherminier Pascale²

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.

Journal of Geophysical Union - Research C - Oceans (0148-0227) (American Geophysical Union), 2005-06 , Vol. 110 , N. C7

5

Climatology-Meteorology, Geology, Physical Oceanography

Turbulent mixing, Tnertia gravity waves

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.