Satellite investigation of the M-2 Internal Tide in the Tasman Sea

TitleSatellite investigation of the M-2 Internal Tide in the Tasman Sea
Publication TypeJournal Article
Year of Publication2018
AuthorsZhao Z.X, Alford MH, Simmons H.L, Brazhnikov D., Pinkel R
JournalJournal of Physical Oceanography
Volume48
Pagination687-703
Date Published2018/03
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000430757700013
Keywordscentral north pacific; continental-slope; deep-ocean; energy; global patterns; gravity-waves; Luzon Strait; model; new-zealand; oceanography; propagation
Abstract

The M-2 internal tide in the Tasman Sea is investigated using sea surface height measurements made by multiple altimeter missions from 1992 to 2012. Internal tidal waves are extracted by two-dimensional plane wave fits in 180 km by 180 km windows. The results show that the Macquarie Ridge radiates three internal tidal beams into the Tasman Sea. The northern and southern beams propagate respectively into the East Australian Current and the Antarctic Circumpolar Current and become undetectable to satellite altimetry. The central beam propagates across the Tasman Sea, impinges on the Tasmanian continental slope, and partially reflects. The observed propagation speeds agree well with theoretical values determined from climatological ocean stratification. Both the northern and central beams refract about 158 toward the equator because of the beta effect. Following a concave submarine ridge in the source region, the central beam first converges around 45.5 degrees S, 155.5 degrees E and then diverges beyond the focal region. The satellite results reveal two reflected internal tidal beams off the Tasmanian slope, consistent with previous numerical simulations and glider measurements. The total energy flux from the Macquarie Ridge into the Tasman Sea is about 2.2 GW, of which about half is contributed by the central beam. The central beam loses little energy in its first 1000-km propagation, for which the likely reasons include flat bottom topography and weak mesoscale eddies.

DOI10.1175/jpo-d-17-0047.1
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