Most reconstructions of the South American Monsoon System (SAMS) over the last two millennia are based on δ18O records from locations at high-elevation sites in the Andes, which are not influenced by the South Atlantic Convergence Zone (SACZ). Yet the SACZ is a key driver of SAMS variability over much of Brazil. Here we use two new δ18O records from speleothems sampled in the central and southwestern portions of the SACZ core to show that the SAMS was not varying in phase over the entire tropical continent during the last two millennia. In fact, speleothem records located to the northeast of the SACZ record precipitation variations that are antiphased with similar records on the opposite side of the SACZ, in particular during the Little Ice Age period, while records close to the core of the SACZ axis show no significant departure from the mean state during this period.
Bibliographical noteFunding Information:
We thank Alyne Barros and Osmar Antunes for their support during the stable isotope data acquisition at the University of São Paulo. We are grateful to ICMBio for permission to collect stalagmite samples. This work was supported by the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP), Brazil (grants 2012/01187-4 and 2016/00299-4 to I. K.; 2009/12902-3 fellowship to M. S. P; 2012/03942-4, 2014/10095-1, 2015/08351-2, 2016/15807-5, and 2017/23687-2 fel lowships to V. F. N.; and 2012/50260-6, 2013/50297, and 2017/50085-3 PIRE NSF-FAPESP to F. W. C.), INCLINE/USP and PRIMO cooperative project (CNPq- IRD) to F. W. C, and the U.S. National Science Foundation (NSF) grants AGS- 1303828 and PIRE-NSF 1743738 to M. V. and 1103403 to R. L. E and H. C. The data presented in this paper can be found in the supporting information.
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- South American Monsoon
- South Atlantic Convergence Zone