Internal tide coherence and decay over a wide shelf sea

Abstract

A quasi-synoptic hydrography and velocity section is used to determine the structure and the decay rate of the internal tide (IT) across the broad continental shelf of the Celtic Sea. In these observations the IT is coherent over more than 170 km, about five wavelengths, with an estimated shoreward energy decay scale of 42 km. The inferred IT wavelength-averaged dissipation rate near the shelf edge is estimated as 2.08 × 10 -7 Wkg -1, in close agreement with tidally-and vertically-averaged measurements from the region. These results provide the first in situ evidence of IT coherence over many wavelengths in a shelf sea. Copyright 2011 by the American Geophysical Union.