EarthRef.org Reference Database (ERR)
Development and Maintenance by the EarthRef.org Database Team

Detailed Reference Information
Nagasawa et al. 2002
Nagasawa, M., Hibiya, T., Niwa, Y., Watanabe, M., Isoda, Y., Takagi, S. and Kamei, Y. (2002). Distribution of fine-scale shear in the deep waters of the North Pacific obtained using expendable current profilers. Journal of Geophysical Research 107: doi: 10.1029/2002JC001376. issn: 0148-0227.

Recent numerical experiments <Hibiya et al., 1996, 1998, 2002> predicted that the energy cascade across the internal wave spectrum down to small dissipation scales was under strong control by parametric subharmonic instabilities that transfer energy from the low vertical wave number, double-inertial frequency wave band to a high vertical wave number, near-inertial frequency wave band. To test whether or not the numerically predicted energy cascade process is actually dominant in the real deep ocean, we deployed a total of 106 expendable current profilers over a large area in the North Pacific to examine the spatial distribution of high vertical wave number (vertical wavelength ~25 m) shear. At midlatitudes, significant enhancement of the 25 m vertical shear was found over prominent generation regions of semidiurnal internal tides such as the Hawaiian Ridge and the Izu-Ogasawara Ridge where the semidiurnal tidal frequency exceeds twice the local inertial frequency. At high latitudes, in contrast, no significant enhancement of the 25 m vertical shear was found to occur even over another prominent generation region of semidiurnal internal tides, the Aleutian Ridge, where the semidiurnal tidal frequency is less than twice the local inertial frequency. We find that the spatial distribution of the intensity of the 25 m vertical shear correlates very well with that of the low vertical wave number, double-inertial frequency internal wave energy numerically predicted by Nagasawa et al. <2000> and Niwa and Hibiya <2001a, 2001b>. This is the first in situ evidence for the dominant role of parametric subharmonic instability in transferring deep ocean internal wave energy down to small dissipation scales. This study provides a theoretical framework for future attempts to determine the large-scale structure of mixing over the world's oceans.

BACKGROUND DATA FILES

Abstract

Keywords
Oceanography, Physical, Internal and inertial waves, Oceanography, Physical, Fine structure and microstructure, Oceanography, Physical, Turbulence, diffusion, and mixing processes
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
2000 Florida Avenue N.W.
Washington, D.C. 20009-1277
USA
1-202-462-6900
1-202-328-0566
service@agu.org
Click to clear formClick to return to previous pageClick to submit