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

TitleReflection of linear internal tides from realistic topography: The Tasman continental slope
Publication TypeJournal Article
Year of Publication2016
AuthorsKlymak J.M, Simmons H.L, Braznikov D., Kelly S., MacKinnon JA, Alford MH, Pinkel R, Nash J.D
JournalJournal of Physical Oceanography
Date Published2016/11
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000389036600005
Keywordsenergetics; frequencies; islands; ocean; ridge; seamounts

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 the mode-1 internal tide as mode 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.

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