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Internal tide spatial variability off western Portugal detected by current meter observations
Author(s) -
Dias Joaquim
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl024957
Subject(s) - geology , internal tide , current meter , kinetic energy , continental shelf , geodesy , internal wave , spectral line , harmonics , geophysics , physics , atmospheric sciences , oceanography , quantum mechanics , astronomy , voltage
Long‐term (10–12 months) current meter observations from the western Iberian continental margin are analyzed focusing on oscillations in the internal gravity wave band. Kinetic energy spectra are characterized by background falloff rates with frequency ω ranging from ω −1 to ω −2 , superposed by energetic narrow bands at specific frequencies. Significant spectral peaks are found at some of the inertial‐tidal nonlinear interaction frequencies (M 2 + f and M 4 + f) and at higher semidiurnal harmonics (M 4 , M 6 and M 8 ). Semidiurnal internal tide kinetic energy reveals a spatial distribution with a maximum coherent contribution (44 cm 2 s −2 ) at 1200‐m depth on the mid continental slope and a maximum relative incoherent signal (>60% of the total semidiurnal tidal band energy) at intermediate levels (650 to 1200 m depth and 30 to 130 km from the shelf break).