Stability properties of a barotropic surface-water jet observed in the Denmark Strait

Observational data from a transect of the Denmark Strait have shown a rapid (1 m/s) southward-flowing barotropic surface jet. A linear stability analysis of the jet suggests that it may be unstable with respect to wave like perturbations. The most unstable wave proved to be sinuous, i.e., meandering, with a growth rate of around 19 h (in terms of an e-folding time), a phasevelocity of approximately 25 cm/s and wavelengths of around 40 km. Associated hydrographic data indicate that the local mixing of the surface waters predominantly is isopycnic. A possible explanation of this observed water-mass distribution could be that the jet initiated cross-channel water transports as the meandering instabilities grew with time. It must, however, be emphasised that since the stability properties of the jet are mainly locally determined, an overall description of the mixing processes in the area cannot be accomplished without invoking the along-streamvariations of the flow.