E.Coelho ferreira.coelho@hidrografico.pt
Instituto Hidrografico, PT-1000 Lisboa, Portugal
S.M. Jesus sjesus@ualg.pt
SiPLAB-FCT, Universidade do Algarve, PT-8000 Faro, Portugal
Y. Stephan stephan@shom.fr
and X. Demoulin demoulin@shom.fr
CMO-EPSHOM, F-29275 Brest, France
M.B. Porter michael.porter@njit.edu
Math. Dept., New Jersey Inst. of Technol., Newark, NJ 07102, USA
Comments: download pdf file .
Ref.: in 133th Meeting
of the Acoustical Society of America, Penn State, Pennsylvania, (USA),
Vol.111, No.5, Pt.2,
p.3015-3016, June 1997.
Abstract : As is well-known, the tidal force of the moon and the sun can cause notable
changes in the sea level. Besides this so-called barotropic effect, the tidal force also drives
internal waves in a daily rhythm. Thus, the internal wave spectrum is often dominated by a single
component with perhaps 10 km from crest to crest. This ``internal tide'' tends to propagate toward
shore and has its greatest height near the shelfbreak. As this tide propagates it modulates the
surface duct and its acoustic signature is often seen in data. The Intimate '96 experiment
(conducted off the coast of Portugal) was specifically designed to acoustically image the internal
tide with an eye toward a more precise understanding of its structure and acoustic impact. A towed
source emitted chirps every 8 s for several days and the chirps were received on the SACLANTCEN
portable array. The data show a textbook multipath structure with early refracted paths followed
by some 30 distinct bottom and surface echoes which shift with the internal tide. The acoustic and
oceanographic interpretation of this data will be discussed.
ACKNOWLEDGMENT: this work was partially supported by the EU project MAS2-CT920022.