Observation of Non Linear Internal Waves on the Landes Shelf (Bay of Biscay)

Other titles Observation d'ondes internes non linéaires sur le Plateau des Landes (Golfe de Gascogne)
Type Poster
Date 2022-03-02
Language English
Other localization https://www.aslo.org/osm2022/
Author(s) Moncuquet Adele1, 2, Dufois Francois1, Jones Nicole3, Bordois Lucie4, Grasso FlorentORCID1, Lazure PascalORCID2
Affiliation(s) 1 : DYNECO / IFREMER Brest, France
2 : LOPS / IFREMER Brest, France
3 : UWA Ocean Institute, Perth Australia
4 : SHOM, Brest, France
Meeting OSM 2022 - Ocean Science Meeting “Come Together and Connect”. 24 february - 4 march 2022, Online everywhere

The Bay of Biscay (Bob) is a hotspot of internal tide and non-linear internal wave generation. Yet, the internal waveson the inner shelf have never been observed nor described. An oceanographic campaign has been conducted overthe Landes shelf (Southern BoB) during the summer of 2017 to better characterize internal wave dynamics. Usingvelocity current profiles, thermistor chains and MVP (Moving Vessel Profiler) measurements in 65m water depth, wehere describe a part of the first field observations of non-linear internal waves (NLIWs) on the southern shelf of theBay of Biscay. Frequent NLIWs, characterized by isotherm excursions up to 20m and vertical currents of 0.2m/s, wereobserved. NLIWs of depression propagate close to the surface and polarity reversal was evidence for some of thoseNLIWs. No polarity reversals were observed when background stratification was maximum close to the seafloor.Trains of NLIWs of elevation, associated with a maximum density gradient close to the bottom, were observed at thebeginning of the campaign. The latter observation seems to be linked to a deep cold water advection. Velocity measurements show two flow regions within the wave frame of reference. The backscatter signal is used to proxysuspended materials and showed different responses depending on the flow region. In conclusion, we observechanges in the NLIWs response with the background stratification. Clear elevation and depression NLIWs exist whenthere was strong near-bed stratification. Twenty days later, maximum stratification was in the middle of the watercolumn and packets of mixed polarity waves were observed. Increased backscatter signal within the core of someNLIWs suggests that they could potentially impact the dynamics of near-bed material. However, the processesinducing increased backscatter have not been identified, and dedicated measurements will be conducted in the futureto better understand the underlying mechanisms.

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Moncuquet Adele, Dufois Francois, Jones Nicole, Bordois Lucie, Grasso Florent, Lazure Pascal (2022). Observation of Non Linear Internal Waves on the Landes Shelf (Bay of Biscay). OSM 2022 - Ocean Science Meeting “Come Together and Connect”. 24 february - 4 march 2022, Online everywhere. https://archimer.ifremer.fr/doc/00767/87888/