Shut down of the South American summer monsoon during the penultimate glacial

Paula Rodríguez-Zorro (1) , Marie-Pierre Ledru (1, 2) , Edouard Bard (3) , Olga Aquino-Alfonso (1) , Adriana Camejo (4) , Anne-Laure Daniau (5) , Charly Favier (1) , Marta Garcia (6) , Thays Mineli (7) , Frauke Rostek (6) , Fresia Ricardi-Branco (4) , André Oliveira Sawakuchi (7) , Quentin Simon (6) , K. Tachikawa (6) , Nicolas Thouveny (6)

1 UMR ISEM - Institut des Sciences de l'Evolution de Montpellier
2 IRD - Institut de Recherche pour le Développement
3 Collège de France - Chaire Evolution du climat et de l'océan
4 UNICAMP - Universidade Estadual de Campinas = University of Campinas
5 EPOC - Environnements et Paléoenvironnements OCéaniques
6 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
7 USP - Universidade de São Paulo = University of São Paulo

We analysed changes in mean annual air temperature (MAAt), vegetation and biomass burning on a long and continuous lake-peat sediment record from the colônia basin, southeastern Brazil, examining the responses of a wet tropical rainforest over the last 180 ka. Stronger southern atmospheric circulation up to the latitude of colônia was found for the penultimate glacial with lower temperatures than during the last glacial, while strengthening of the South American summer monsoon (SASM) circulation started during the last interglacial and progressively enhanced a longer wet summer season from 95 ka until the present. Past MAAT variations and fire history were possibly modulated by eccentricity, although with signatures which differ in average and in amplitude between the last 180 ka. Vegetation responses were driven by the interplay between the SASM and southern circulation linked to Antarctic ice volume, inferred by the presence of a cool mixed evergreen forest from 180 to 45 ka progressively replaced by a rainforest. We report cooler temperatures during the marine isotope stage 3 (MIS 3: 57-29 ka) than during the Last Glacial Maximum (LGM: 23–19 ka). Our findings show that tropical forest dynamics display different patterns than mid-latitude during the last 180 ka.

Domaines: Climatologie; Milieux et Changements globaux

Paula Rodríguez-Zorro, Marie-Pierre Ledru, Edouard Bard, Olga Aquino-Alfonso, Adriana Camejo, et al.. Shut down of the South American summer monsoon during the penultimate glacial. Scientific Reports, 2020, 10, pp.6275. ⟨10.1038/s41598-020-62888-x⟩. ⟨hal-02543791⟩