Reflection of linear internal tides from realistic topography: The Tasman continental slope

Citation:
Klymak, JM, Simmons HL, Braznikov D, Kelly S, MacKinnon JA, Alford MH, Pinkel R, Nash JD.  2016.  Reflection of linear internal tides from realistic topography: The Tasman continental slope. Journal of Physical Oceanography. 46:3321-3337.

Date Published:

2016/11

Keywords:

energetics, frequencies, Islands, ocean, ridge, seamounts

Abstract:

The reflection of a low-mode internal tide on the Tasman continental slope is investigated using simulations of realistic and simplified topographies. The slope is supercritical to the internal tide, which should predict a large fraction of the energy reflected. However, the response to the slope is complicated by a number of factors: the incoming beam is confined laterally, it impacts the slope at an angle, there is a roughly cylindrical rise directly offshore of the slope, and a leaky slope-mode wave is excited. These effects are isolated in simulations that simplify the topography. To separate the incident from the reflected signal, a response without the reflector is subtracted from the total response to arrive at a reflected signal. The real slope reflects approximately 65% of themode-1 internal tide asmode 1, less than two-dimensional linear calculations predict, because of the three-dimensional concavity of the topography. It is also less than recent glider estimates, likely as a result of along-slope inhomogeneity. The inhomogeneity of the response comes from the Tasman Rise that diffracts the incoming tidal beam into two beams: one focused along beam and one diffracted to the north. Along-slope inhomogeneity is enhanced by a partially trapped, superinertial slope wave that propagates along the continental slope, locally removing energy from the deep-water internal tide and reradiating it into the deep water farther north. This wave is present even in a simplified, straight slope topography; its character can be predicted from linear resonance theory, and it represents up to 30% of the local energy budget.

Notes:

n/a

Website

DOI:

10.1175/jpo-d-16-0061.1