Application of an internal tide generation model to baroclinic spring-neap cycles

Abstract

A numerical internal tide generation model is used to study the behavior of baroclinic spring-neap cycles in open basins and channels. The motivation for this study comes from an observation on tidal currents in Faeroe-Shetland Channel, which is briefly described; a surprisingly large baroclinic semidiurnal tidal signal is found in the lower part of the water column above the slope on the Shetland side, concurring with barotropic neap tides. The numerical model results indeed show that the baroclinic spring-neap cycle may have a phase shift with respect to the barotropic spring-neap cycle and that the phase of the baroclinic cycle may vary strongly within short distances. It is also shown that even small changes in the background conditions (e.g., stratification) can provoke a large phase shift in the baroclinic cycle; a possible connection to "intermittency" is discussed.