THE EFFECTS OF STRATIFICATION AND ALONGSHORE CURRENTS ON THE PROPAGATION OF COASTAL-TRAPPED WAVES

A hierarchy of models has been developed to describe coastal-trapped w ave (CTW) propagation along continental shelves. In this paper, the re sults of four models are compared with respect to predictions of phase speeds for low-frequency non-dispersive CTWs propagating through the ACE (Australian Coastal Experiment) study area along the southeast Aus tralian coast. The ACE experiment demonstrated that the stratification there significantly increased theoretical CTW phase speeds. At times substantial mean alongshore currents, apparently associated with meand ers of the East Australian Current, were observed to intrude onto the continental shelf. Such currents can alter CTW propagation speeds by a dvection and by altering background vorticity if the current has shear . Accordingly, the models chosen here for intercomparsion incorporate first, no stratification and no current [BUCHWALD and ADAms, (1968) Pr oceedings of the Royal Society Series A, 305, 235-250]; secondly, baro tropic currents and no stratification [NIILER and MYSAK (1971), Geophy sical Fluid Dynamics, 2,273-288]; thirdly, vertical stratification but no currents (HUTHNANCE (1978), Journal of Physical Oceanography, 8, 7 4-92]; and fourthly, full stratification and baroclinic currents [LUTH ER and BANE (1985) Journal of Physical Oceanography, 15, 3-23]. The st ratification and currents used in these models were determined from CT D casts and ship drift data obtained during six ACE cruises. Between t he six cruises the oceanographic conditions on the shelf and offshore were observed to undergo considerable variation. Hence, it has been po ssible to compare the models over a wide range of parametric variation s. The results show that there is considerable variation in the predic ted phase speeds between models.