Decay mechanisms of near-inertial mixed layer oscillations in the Bay of Bengal

TitleDecay mechanisms of near-inertial mixed layer oscillations in the Bay of Bengal
Publication TypeJournal Article
Year of Publication2016
AuthorsJohnston T.MS, Chaudhuri D., Mathur M., Rudnick D.L, Sengupta D., Simmons H.L, Tandon A., Venkatesan R.
JournalOceanography
Volume29
Pagination180-191
Date Published2016/06
Type of ArticleArticle
ISBN Number1042-8275
Accession NumberWOS:000380572500021
Keywordscurrents; events; geostrophic flow; internal waves; models; ocean; propagation; Shear; transition layer; wind
Abstract

Winds generate inertial and near-inertial currents in the upper ocean. These currents dominate the kinetic energy and contain most of the vertical shear in horizontal currents. Subsequent shear instabilities lead to mixing. In the Bay of Bengal, the annual mean wind energy input and near-inertial mixed layer energy is almost as large as in the mid-latitude storm tracks. Also, mixing associated with these waves is known to affect mixed layer heat content, sea surface temperature, and, thus, precipitation in coupled global models. Therefore, the mechanisms leading to the decay of these currents in the mixed layer and below are of considerable importance. Two such decay mechanisms are examined here. One mechanism is the downward propagation of near-inertial internal waves, which is aided by the mesoscale circulation and is observed with a rapidly profiling float. In a few days (faster than at mid-latitudes), the near-inertial wave group propagated from the base of the mixed layer to 250 m depth in the stratified interior. Another decay mechanism is enhanced shear generation at the mixed layer base from periodic alignment of rotating, near-inertial current shear and winds, which is observed with a mooring and analyzed with a simple two-layer model.

DOI10.5670/oceanog.2016.50
Short TitleOceanography
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