title: Equatorial Pacific forcing of western Amazonian precipitation during Heinrich Stadial 1.
abstract: 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.
authors: MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.
authors: Yancheng
authors: Y
authors: Zhang
authors: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors: Xu
authors: X
authors: Zhang
authors: School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil.
authors: Cristiano M
authors: CM
authors: Chiessi
authors: MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.
authors: Stefan
authors: S
authors: Mulitza
authors: MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.
authors: Xiao
authors: X
authors: Zhang
authors: MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.|Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors: Gerrit
authors: G
authors: Lohmann
authors: MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.
authors: Matthias
authors: M
authors: Prange
authors: Department of Palynology and Climate Dynamics, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Germany.
authors: Hermann
authors: H
authors: Behling
authors: MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.
authors: Matthias
authors: M
authors: Zabel
authors: IPSL/LSCE, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-UVSQ), Université Paris Saclay, Gif sur Yvette, France.
authors: Aline
authors: A
authors: Govin
authors: Institute of Geosciences, University of São Paulo, São Paulo, Brazil.
authors: André O
authors: AO
authors: Sawakuchi
authors: Institute of Geosciences, University of São Paulo, São Paulo, Brazil.
authors: Francisco W
authors: FW
authors: Cruz
authors: MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.
authors: Gerold
authors: G
authors: Wefer