Little Ice Age dryness in Northeast Brazil recorded by lacustrine sediments of lake Boqueirão explains discrepancies between 14 C and 210 Pb measurements

• Main Authors: Turcq, Bruno, Zocatelli, Renata, Costa, Renata Lima, Cordeiro, Renato Campello, Luiza Spadano Albuquerque, Ana, Mandeng Yogo, Magloire
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL), 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-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)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Departamento de Geoquímica, Universidade Federal Fluminense Rio de Janeiro (UFF)
• Format: Conference Object
• Language: English
• Published: CCSD 2012
• Subjects: [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDE.MCG]Environmental Sciences/Global Changes; North Atlantic
• Online Access: https://insu.hal.science/insu-00843366

International audience Lake Boqueirão is located at 5°S latitude, on the Brazilian Atlantic coast, a region where the climate is directly influenced by the Intertropical Convergence Zone (ITCZ) displacements. Two cores were collected at different water depths based on a seismic survey. 210 Pb were measured in the top 20 cm and 14 C all along the profiles. The two methods indicated very different results concerning ages and sedimentation rates of the sediment. Lake level changes has been reconstructed using granulometry, Total Organic Carbon, C/N, 13 C, 15 N and Rock Eval (Hydrogen Index (HI), Oxygen Index (OI)). These proxies indicate large variations of the lake levels during the last 3000 cal yrs BP. Moreover, a prolonged dryness occurred in Lake Boqueirão since 570 cal yrs BP, till the last decades. This event provoked a drying of the lake at the two sampling sites. This drying can explains why the 210 Pb method did not work in this lake probably due to an enrichment phenomenon of bare surfaces called " meteoric cap ". This dry phase corresponds to the Little Ice Age characterized by a cooler North Atlantic Ocean. These data indicate that the teleconnection pattern between tropical Atlantic, ENSO and Northeast Brazil rainfalls has changed in the past 3000 years.