Internal waves along the malvinas current: Evidence of transcritical generation in satellite imagery

Abstract

An extended satellite image data set is used to investigate the two-dimensional structure of internal waves (IWs) that propagate along the Patagonian shelf break and continental slope in the opposite direction of the Malvinas Current (MC). Intense surface manifestations of IWs are found throughout the semidiurnal and fortnightly tidal cycles, propagating more than 1,000 km in the along-slope direction between 38°S and 48°S. An instantaneous 800 km view provided by the Sentinel-2A satellite multispectral imager shows a nearly continuous IW field in which inter-packet distances do not fit the usual semidiurnal tidal scales observed in coastal waters. Instead, acoustic Doppler current profiler-measured currents and CTD station data are consistent with resonant generation mechanisms in which the MC flows over bottom topography and generates upstream-propagating waves in a transcritical regime. These conditions are known to cause extra dissipation and mixing, whose effects over time and along more than 1,000 km may be important to a wider scope of ocean applications.