On topography-related dynamics in the Argentine Basin

• Main Author: Poli, Léa
• Other Authors: Austral, Boréal et Carbone (ABC), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Sorbonne Université, Jérôme Sirven, Camila Artana
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2023
• Subjects: Physical Oceanography; Dynamics; Tropographic Waves; Variability; Topography; Océanographie physique; Dynamique; Ondes topographiques; Variabilité; Topographie; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Drake Passage
• Online Access: https://theses.hal.science/tel-04391274; https://theses.hal.science/tel-04391274/document; https://theses.hal.science/tel-04391274/file/POLI_Lea_these_2023.pdf

The Argentine Basin (>5000 m) is home to rather unique oceanic structures of prime importance to the global circulation. In this thesis, we focus on elements of circulation (ocean waves and currents) constrained by topography. To the west, the Patagonian continental shelf of variable slope and direction hosts a variety of topographic waves. By combining outputs of a high-resolution reanalysis (GLORYS12), in-situ and satellite data, two types of sub-inertial waves were documented, fast and slow waves. Fast waves propagating along the Patagonian shelf break, with phase velocities between 1 m/s and 7 m/s, periods ranging from 5 to 130 days and wavelengths from 1,200 to 12,000 km. Their characteristics depend upon stratification, slope, shelf width, latitude and mean flow. High-frequency waves with periods between 5 and 40 days are often locally forced by strong variations of the zonal wind south of 47°S(Poli et al.,2020), whereas lower-frequency waves with periods between 40 and 130 days propagate from the equatorial Pacific to the tropical Atlantic (22°S, Poli et al.,2022). The Madden-Julian Oscillation (MJO) plays a key role in forcing these low-frequency waves in two ways. (a) By an oceanic teleconnection involving equatorial Kelvin waves reaching the American west coast, and (b) by an atmospheric teleconnection reinforcing southerly winds in the southeast Pacific. In addition, local winds, which are not necessarily linked to the MJO, modulate and trigger low-frequency waves (40-130 days period) in specific locations, such as the Brazil-Malvinas confluence and the Drake Passage. All these waves have an impact on along-shore currents : during the positive phase, the near-surface current is increased by around 0.1 m/s. In addition, these waves contribute to the supply of nutrients sustaining the high primary production on the Patagonian shelf. Slow waves propagate in the core of the Malvinas Current with phase velocities between 0.10 and 0.30 m/s, periods around 20, 60 and 100 days, and wavelengths ranging ...