Causes and processes of two opposite climatic years in the tropical Atlantic warm pools

• Published in: Dynamics of Atmospheres and Oceans
• Main Authors: Cintra, Marcio M., Lentini, Carlos A. D., Servain, Jacques, Araujo, Moacyr, Silva, Marcus, Mendes, David
• Other Authors: 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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: Temperature budget; Ocean-atmosphere interannual variability; Atlantic climatic variability modes; Tropical Atlantic warm pools; [SDU]Sciences of the Universe [physics]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Austral; Southern Ocean; North Atlantic; North Atlantic oscillation
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03846479; https://doi.org/10.1016/j.dynatmoce.2022.101337

International audience A numerical investigation of the interannual Southwestern and Equatorial Atlantic warm pools (WPs) (SST>28 °C) was conducted for the 2000-2014 period, focusing on two major opposite events over the past 39 years (1982-2020): an intense warming event in 2010 (sizeable warm pool) and a moderate-to-low event in 2012 (small warm pool). Some modes of climate variability (remote and local) were confronted with the WP area. Significant remote connections were found for the North Atlantic Oscillation (NAO) and the Atlantic Meridional Mode (AMM). Whereas, the Tropical Northern Atlantic (TNA) and Tropical Southern Atlantic (TSA) indices were locally related to anomalies over the WP area. On the months that preceded the 2010 WP event, an anomalous atmospheric circulation in the tropical North Atlantic basin occurred (extremely negative NAO and positive AMM), causing a major weakening of winds, shallower mixed layer, and higher SST. Consequently, the WP boundaries, which usually developed southward along the equator in the austral fall, were pushed northward as warm waters spread out into the north tropical basin. Locally, both basins (i.e., tropical north and south) were warmer than climatologically expected (positive TNA and TSA), leading to a significant increase in the WP area recorded in this period. On the other hand, during the months that preceded the 2012 WP, the trade winds were faster (positive NAO and positive AMM), leading to a condition close to the climatologically expected. The approximation of the center of the subtropical high in the southern ocean basin practically extinguished the portion of warm waters that usually spreads southwest along the basin. While the TNA was weakly positive, the TSA presented negative anomalies that ensured a significant reduction in the WP area in the southern basin during this time. Numerical results from the 2000-2014 run were contrasted with PIRATA buoys and satellite data to assess the model's performance. Investigations of the mixed layer ...