Malvinas Current at 40°S–41°S: first assessment of temperature and salinity temporal variability

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Paniagua, Guillermina, Saraceno, Martin, Piola, Alberto R., Guerrero, Raúl, Provost, Christine, Ferrari, Ramiro, Lago, Loreley, Artana, Camila
• Other Authors: Centro de Investigaciones del Mar y la Atmósfera (CIMA), Facultad de Ciencias Exactas y Naturales Buenos Aires (FCEyN), Universidad de Buenos Aires Buenos Aires (UBA)-Universidad de Buenos Aires Buenos Aires (UBA)-Consejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires (CONICET), Departamento de Ciencias de la Atmosfera y los Oceanos (DCAO), Universidad de Buenos Aires Buenos Aires (UBA)-Universidad de Buenos Aires Buenos Aires (UBA), Instituto Franco-Argentino sobre Estudios de Clima y sus Impactos Buenos Aires (IFAECI), Universidad de Buenos Aires Buenos Aires (UBA)-Universidad de Buenos Aires Buenos Aires (UBA)-Consejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires (CONICET)-Facultad de Ciencias Exactas y Naturales Buenos Aires (FCEyN), Universidad de Buenos Aires Buenos Aires (UBA)-Universidad de Buenos Aires Buenos Aires (UBA)-Consejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires (CONICET)-Centre National de la Recherche Scientifique (CNRS), Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Austral, Boréal et Carbone (ABC), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), 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)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), 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)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU]Sciences of the Universe [physics]; Antarctic; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-02190616; https://hal.archives-ouvertes.fr/hal-02190616/document; https://hal.archives-ouvertes.fr/hal-02190616/file/JGR%20Oceans%20-%202018%20-%20Paniagua%20-%20Malvinas%20Current%20at%2040%20S%2041%20S%20First%20Assessment%20of%20Temperature%20and%20Salinity%20Temporal.pdf; https://doi.org/10.1029/2017JC013666

International audience The temporal variability of 11 months of in situ velocity, temperature, and salinity data collected at five moorings deployed at 40°S–41°S across the shelf-break in the Southwestern Atlantic is analyzed. Two distinct regimes characterized by strong and weak along-slope velocities are present. During the strong regime the Malvinas Current flows northward through the moorings while during the nearly 5months long weak regime reversals of the along-slope velocities are frequently observed. Comparison with the previous in situ time series obtained in the same region shows that such an extended period of weak flow has not been previously observed. During the weak regime, Sub-Antarctic Mode Water is observed over the 1,800 m isobath at an average depth of 500 m. Water masses occupying the upper 1,600 m during the strong regime deepen and shift eastward during the weak period. Satellite geostrophic velocities and sea surface temperature clearly show that the weak regime is due to a deflection to the east of the Malvinas Current, upstream of the mooring position. Analysis of the vertical structure of the currents indicate that during the weak regime the flow weakens mostly at the surface and presents a very small vertical shear. In contrast, during the strong regime currents are surface-intensified. The change in the structure of the cur-rents at the mooring location impacts the relationship between in situ and altimetry-derived currents: during the weak regime altimetry adequately represents (rmsd 12 cm/s) in situ currents in the whole water column, while during strong regime rmsd are larger than 15 cm/s below 600 m depth.