Internal gravity waves in sill fjords: vertical modes, ray theory and comparison with observations.

Abstract

It is well known that marked topographic variations are an important feature by which surface gravity waves can generate internal gravity waves. Typical examples are the generation of internal tides on an abrupt continental shelf and in sill fjords. Two methods of description are available: vertical modes and ray tracing. Both have severe limitations. Decomposition into vertical modes is rigorously justified only if the bottom is horizontal, whereas ray tracing is asymptotically valid only if the wavelengths present are at most a small portion of the total depth. In view of these restrictions, neither method is strictly applicable to the study of internal waves in sill fjords. However, lacking any other applicable techniques, the methods were applied to data from Skjomen, a sill fjord in northern Norway.