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.