ABSTRACT
20Current measurements in the proximity of the western slope of the Norwegian Trench have revealed significant low-frequency (subdiurnal) wave activity. The most prominent observed signal has a period of about 36 h, and is occasionally found to exceed the dominating M 2 tidal constituent.
The purpose of this paper is to give an overview of some of the existing literature concerning this matter. In addition, a model is set up to study wave trapping over a topography approximating a section between Norway and Scotland at a latitude of 60.75°N. In particular this study focuses on the effects of stratification on the frequency of waves trapped over the western slope. A two-layered model is considered in which the upper layer is continuously stratified and the lower layer is homogeneous. The motions are set up by a prescribed wind field. It is apparent from the model studies that the 36 h period is that of the gravest mode wave of zero group speed trapped over the western slope. For a shallow stratification as employed in the numerical experiments, it turns out that the effect of stratification on the frequency is rather small, but depends upon the wavelength. For the zero group speed wave, having a wavelength of about 360 km, the increase in frequency amounts to only about 2%,
