Oceanography The Official Magazine of
The Oceanography Society
Volume 30 Issue 03

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Volume 30, No. 3
Pages 110 - 119

Internal Waves Along the Malvinas Current: Evidence of Transcritical Generation in Satellite Imagery

Jorge M. Magalhães José C.B. da Silva
Article 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.

Citation

Magalhães, J.M., and J.C.B. da Silva. 2017. Internal waves along the Malvinas Current: Evidence of transcritical generation in satellite imagery. Oceanography 30(3):110–119, https://doi.org/10.5670/oceanog.2017.319.

Supplementary Materials

Figure S1. An ensemble of climatological stratifications along the Patagonian shelf break and continental slope (highlighted in the left panel using selected isobaths). The blue envelope represents the maxima in the Brunt-Väisälä frequencies for all austral winter profiles between 200 m and 2,000 m as a function of latitude; average values for July along the 1,000 m isobath are shown as a black solid line. The orange envelope is the same for the austral summer, and in this case the solid black line is for January. > 96 KB pdf 

Figure S2. A mosaic from Sentinel-2A acquisitions dated February 19, 2016, between 22:57 and 23:02 UTC (corresponding to its spectral band 6 centered at 740 nm). Selected isobaths are also given for 200, 500, 1,000, and 2,000 m. > 562 KB pdf | 20.2 MB kmz

Figure S3. A synergy between two RGB composites dated January 31, 2016, acquired at 14:00 UTC (MODIS-Terra) and 17:20 UTC (Suomi-Viirs). > 498 KB pdf | 1.6 MB kmz

Figure S4. An RGB composite from a MODIS-Aqua acquisition dated January 6, 2014, at 17:45 UTC. > 582 KB pdf | 134 KB kmz

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