Topographic scattering of the low-mode internal tide in the deep ocean
Article first published online: 3 APR 2014
© 2014. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Oceans
Volume 119, Issue 4, pages 2165–2182, April 2014
How to Cite
2014), Topographic scattering of the low-mode internal tide in the deep ocean, J. Geophys. Res. Oceans, 119, 2165–2182, doi:10.1002/2013JC009152., , and (
- Issue published online: 13 MAY 2014
- Article first published online: 3 APR 2014
- Accepted manuscript online: 11 MAR 2014 12:55PM EST
- Manuscript Accepted: 6 MAR 2014
- Manuscript Revised: 18 FEB 2014
- Manuscript Received: 29 MAY 2013
- National Science Foundation . Grant Numbers: 0645529 , OCE1129757
- internal tide;
We investigate the role of deep-ocean topography in scattering energy from the large spatial scales of the low-mode internal tide to the smaller spatial scales of higher modes. The complete Green function method, which is not subject to the restrictions of the WKB approximation, is used for the first time to study the two-dimensional scattering of a mode-1 internal tide incident on subcritical and supercritical topography of any form in arbitrary stratifications. For an isolated Gaussian ridge in a uniform stratification, large amplitude critical topography is the most efficient at mode-1 scattering and small amplitude topography scatters with an efficiency on the order of 5–10%. In a nonuniform stratification with a pycnocline, the results are qualitatively the same as for a constant stratification, albeit with the key features shifted to larger height ratios. Having validated these results by direct comparison with the results of nonlinear numerical simulations, and in the process demonstrated that WKB results are not appropriate for reasonable ocean predictions, we proceed to use the Green function approach to quantify the role of topographic scattering for the region of the Pacific Ocean surrounding the Hawaiian Islands chain. To the south, the Line Islands ridge is found to scatter ∼40% of a mode-1 internal tide coming from the Hawaiian Ridge. To the north, realistic, small-amplitude, rough topography scatters ∼5–10% of the energy out of mode 1 for transects of length 1000–3000 km. A significant finding is that compared to large extents of small-amplitude, rough topography a single large topographic feature along the path of a mode-1 internal tide plays the dominant role in scattering the internal tide.