Equatorial Pacific forcing of western Amazonian precipitation during Heinrich Stadial 1

• Published in: Scientific Reports
• Main Authors: Zhang, Yancheng, Zhang, Xu, Chiessi, Cristiano, Mulitza, Stefan, Zhang, Xiao, Lohmann, Gerrit, Prange, Matthias, Behling, Hermann, Zabel, Matthias, Govin, Aline, Sawakuchi, André, Cruz, Francisco, Wefer, Gerold
• Other Authors: Center for Marine Environmental Sciences Bremen (MARUM), Universität Bremen, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Universidade de São Paulo (USP), Nanjing University of Information Science and Technology (NUIST), Albrecht-von-Haller Institut für Pflanzenwissenschaften, Georg-August-University Göttingen, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Climat et Magnétisme (CLIMAG), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology; Pacific; North Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-02180994; https://hal.archives-ouvertes.fr/hal-02180994/document; https://hal.archives-ouvertes.fr/hal-02180994/file/Zhang%28Y%29-SREP2016.pdf; https://doi.org/10.1038/srep35866

International audience Abundant hydroclimatic evidence from western Amazonia and the adjacent Andes documents wet conditions during Heinrich Stadial 1 (HS1, 18-15 ka), a cold period in the high latitudes of the North Atlantic. This precipitation anomaly was attributed to a strengthening of the South American summer monsoon due to a change in the Atlantic interhemispheric sea surface temperature (SST) gradient. However, the physical viability of this mechanism has never been rigorously tested. We address this issue by combining a thorough compilation of tropical South American paleorecords and a set of atmosphere model sensitivity experiments. Our results show that the Atlantic SST variations alone, although leading to dry conditions in northern South America and wet conditions in northeastern Brazil, cannot produce increased precipitation over western Amazonia and the adjacent Andes during HS1. Instead, an eastern equatorial Pacific SST increase (i.e., 0.5-1.5 °C), in response to the slowdown of the Atlantic Meridional Overturning Circulation during HS1, is crucial to generate the wet conditions in these regions. The mechanism works via anomalous low sea level pressure over the eastern equatorial Pacific, which promotes a regional easterly low-level wind anomaly and moisture recycling from central Amazonia towards the Andes.