Annual Cycle and Depth Penetration of Wind-Generated Near-Inertial Internal Waves at Ocean Station Papa in the Northeast Pacific
| Type | : | ACL |
|---|---|---|
| Nature | : | Production scientifique |
| Au bénéfice du Laboratoire | : | Non |
| Statut de publication | : | Publié |
| Année de publication | : | 2012 |
| Auteurs (3) | : | ALFORD Matthew,h CRONIN M,f KLYMAK Jody,m |
| Revue scientifique | : | Journal of Physical Oceanography |
| Volume | : | 42 |
| Fascicule | : | 6 |
| Pages | : | 889-909 |
| DOI | : | 10.1175/JPO-D-11-092.1 |
| URL | : | - |
| Abstract | : | The downward propagation of near-inertial internal waves following winter storms is examined in the context of a 2-yr record of velocity in the upper 800 m at Ocean Station Papa. The long time series allow accurate estimation of wave frequency, whereas the continuous data in depth allow separation into upward- and downward-propagating components. Near-inertial kinetic energy (KEin) dominates the record. At all measured depths, energy in downgoing motions exceeds that of upward-propagating motions by factors of 3-7, whereas KEin is elevated by a factor of 3-5 in winter relative to summer. The two successive winters are qualitatively similar but show important differences in timing and depth penetration. Energy is seen radiating downward in a finite number of wave groups, which are tagged and catalogued to determine the vertical group velocity c, which has a mean of about 1.5 x 10(-4) m s(-1) (13 m day(-1)). Case studies of three of these are presented in detail. Downward energy flux is estimated as c(gz) X KEin (i) by summing over the set of events, (ii) from time series near the bottom of the record, and (iii) from the wavenumber-frequency spectrum and the dispersion relationship. These estimates are compared to the work done on near-inertial motions in the mixed layer by the wind, which is directly estimated from mixed layer near-inertial currents and winds measured from a surface buoy 10 km away. All three methods yield similar values, indicating that 12%-33% of the energy input into the mixed layer transits 800 m toward the deep sea. This simple picture neglects lateral energy flux carried by the first few vertical modes, which was not measured. The substantial deep penetration implies that near-inertial motions may play a role in mixing the deep ocean, but the strong observed variability calls for a need to better understand the role of lateral mesoscale structures in modulating the vertical propagation. |
| Mots-clés | : | ALTIMETER DATA; DEEP-OCEAN; ENERGY FLUX; GEOSTROPHIC FLOW; KINETIC-ENERGY; MENDOCINO ESCARPMENT; STRONG STORM; SURFACE MIXED-LAYER; VELOCITY PROFILES; WAVENUMBER-FREQUENCY-SPECTRUM |
| Commentaire | : | Times Cited in Web of Science Core Collection: 86 |
| Tags | : | - |
| Fichier attaché | : | - |
| Citation | : |
Alford MH, Cronin MF, Klymak JM (2012) Annual Cycle and Depth Penetration of Wind-Generated Near-Inertial Internal Waves at Ocean Station Papa in the Northeast Pacific. J Phys Oceanogr 42: 889-909 | doi: 10.1175/JPO-D-11-092.1
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