Intra‐ and inter‐annual variability of North Brazil current rings using angular momentum Eddy detection and tracking algorithm: observations from 1993 to 2016

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Aroucha, L.C., Veleda, Dóris, Lopes, F. S., Tyaquiçã, Pedro, Lefèvre, Nathalie, Araujo, Moacyr
• Other Authors: Laboratory of Physical, Coastal and Estuarine Oceanography (LOFEC), Federal University of Pernambuco Recife, 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)-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)-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)), 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)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Center for Risk Analysis and Environmental Modeling - CEERMA. Federal University of Pernambuco, Recife, PE, Brazil., European Project: 817578,TRIATLAS(2019)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; North Atlantic
• Online Access: https://hal.science/hal-03145630; https://hal.science/hal-03145630/document; https://hal.science/hal-03145630/file/JGR%20Oceans%20-%202020%20-%20Aroucha%20-%20Intra%25E2%2580%2590%20and%20Inter%25E2%2580%2590Annual%20Variability%20of%20North%20Brazil%20Current%20Rings%20Using%20Angular%20Momentum%20Eddy.pdf; https://doi.org/10.1029/2019JC015921

International audience In order to investigate intra- and inter-annual variability of North Brazil Current (NBC) rings, angular momentum eddy detection and tracking algorithm (AMEDA) was used for identification of their occurrence, trajectories, and parameters. Based on 24 years (1993–2016) of geopotential height and geostrophic current fields reanalysis data from ARMOR 3D (¼°), we identified an average rate of five NBC rings shed by year. The rings present an average lifetime of 15.3 (±5.4) weeks, average speed based radius ($R_{max}$) of 139.8 (±23.6) km, and mean sea surface height anomaly (SSHa) of 9.4 (±4.0) cm. The mean observed maximum azimuthal velocity ($V_{max}$) was 0.27 (±0.08) m/s, while the averaged Rossby number (Ro) value was 0.08 (±0.04) and averaged kinetic energy (KE) was of 255.3 (±154.8) cm2 /s2 . NBC rings have larger dimensions, rotate faster, live less, and transfer more energy in boreal winter months. In contrast, those shed during boreal summer and early fall last longer, have smaller diameters and carry less energy. Besides, the analysis of ring merging pointed that the interaction between NBC rings generated a significantly increase in ring energy (52%), and velocity (22%). Finally, we observed the vertical anomalies temperature and salinity profiles, which indicated a thermocline deepening and sinking of coastal and tropical waters due to NBC rings downwelling. This study emphasizes the robustness and efficiency of AMEDA for studying rings in the ocean and further theorizes possible impacts of NBC ring on ocean physical and biogeochemical features in the Western Tropical North Atlantic.