Anatomy of subinertial waves along the Patagonian shelf break in a 1/12° global ocean reanalysis.

Léa Poli (LOCEAN,Sorbonne Université, France)

CoAuthors

Camila Artana (Mercator Océan, France); Christine Provost (LOCEAN, Sorbonne Université, CNRS, France); Jérôme Sirven (LOCEN, Sorbonne Université, France); Nathalie Sennéchael (LOCEAN, Sorbonne Université, France); Yannis Cuypers (LOCEAN, Sorbonne Université, France); Jean Michel Lellouche (Mercator Ocean, France)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Science III: Mesoscale and sub-mesoscale oceanography

Presentation type: Type Forum

The Malvinas Current (MC) carries subantarctic waters along the Patagonian slope. Those nutrient-rich waters play a key role in the development of massive phytoplankton blooms observed over the continental shelf and shelf-break (with chlorophyll concentrations as large as 2.5-3.0 mg/m3). Topographically trapped waves at the shelf-break could enhance the fluxes of nutrients towards the continental shelf.
The sinuous Patagonian continental slope hosts a variety of waves. We used a state-of-the-art ocean reanalysis (25 years of Mercator Ocean GLORYS12) to examine waves at the shelf break and in the core of the MC at periods larger than 5 days.
Statistics over 25 years indicate three types of signals: in phase signals at specific locations of the shelf break to the south of 47°S, fast propagating signals all along the shelf break (with phase speeds in the range 1.4 - 3.0 cm/s) at periods between 5 and 110 days, and slower signals in the core of the MC (with phase speeds between 0.1 and 0.3 m/s) at 20-day, 60-day and 100-day periods.
The large zonal wind stress variations south of 47°S force in-phase along-slope velocity variations and trigger fast propagating waves at distinct sites corresponding to abrupt changes in the shelf break orientation. The modal structures, phase velocities, wavelengths and periods of those fast waves are consistent with linear theory. Period-wavelength spectrum of along-shore velocities at the shelf-break shows energy patterns in line with theoretical dispersion curves of mode 2 to 4. The shelf-break waves have spatial structures and temporal scales congruent with those of observed upwelling events.
Slow propagating waves in the core of the MC have along-slope wavelengths between 450 and 1200 km and are remotely forced. They were tracked back to the Drake Passage and the Malvinas Escarpment.
The Patagonian slope abruptly changes orientation and shape. Thus, the wave characteristics evolve during their northward propagation (frequencies, wavelengths, phase speeds and modal structure).
Reference:
Poli L,. C Artana, C. Provost, J. Sirven, N. Sennéchael, Y. Cuypers, J-M. Lellouche, (2020), Anatomy of subinertial waves along the Patagonian shelf break in a 1/12° global operational model. Journal Geophysical Research, Oceans, doi:10.1029/2020JC016549 (revised).
 
Léa Poli
LOCEAN,Sorbonne Université
France
lpoli@locean-ipsl.upmc.fr