Temporal Variability of High Vertical Wavenumber Shear over the Izu-Ogasawara Ridge |
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| Authors: | Email author" target="_blank">Maki?NagasawaEmail author Toshiyuki?Hibiya Naoki?Furuichi Shogo?Takagi |
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| Institution: | (1) Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan;(2) Faculty of Fisheries, Hokkaido University, Hakodate 041-8611, Japan |
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| Abstract: | Recent numerical studies (Hibiya et al., 1996, 1998, 2002) showed that the energy cascade across the internal wave spectrum down to small dissipation scales was
under strong control of parametric subharmonic instabilities (PSI) which transfer energy from low vertical mode double-inertial
frequency internal waves to high vertical mode near-inertial internal waves. To see whether or not the numerically-predicted
energy cascade process is actually dominant in the real deep ocean, we examine the temporal variability of vertical profiles
of horizontal velocity observed by deploying a number of expendable current profilers (XCPs) at one location near the Izu-Ogasawara
Ridge. By calculating EOFs, we find the observed velocity profiles are dominated by low mode semidiurnal (∼double-inertial
frequency) internal tides and high mode near-inertial internal waves. Furthermore, we find that the WKB-stretched vertical
scales of the near-inertial current shear are about 250 sm and 100 sm. The observed features are reasonably explained if the
energy cascade down to small dissipation scales is dominated by PSI. |
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| Keywords: | Internal waves internal tide near-inertial waves XCP |
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