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

Abstract

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 beunstable with respect to wavelike 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 hydrographicdata indicate that the local mixing of the surface waters predominantly is isopycnic. A possibleexplanation of this observed water-mass distribution could be that the jet initiated cross-channelwater transports as the meandering instabilities grew with time. It must, however, be emphasisedthat since the stability properties of the jet are mainly locally determined, an overall descriptionof the mixing processes in the area cannot be accomplished without invoking the along-streamvariations of the flow.