Figure 2: Speleothem δ¹⁸O records from western Amazonia in comparison with other climate records.

(a) AM records (purple: Hulu-Dongge caves; dark purple: Sanbao cave)^15,45 and boreal summer (JJA) insolation at 30°N (ref. 47). (b) Southern Brazil records (Botuverá cave)¹⁸ and ASI (DJF) at 30°S(ref. 47). (c) Western Amazon records and ASI (DJF) at 10°S(ref. 47). (d) Niño3 temperature anomalies estimated with the Zebiak and Cane model⁴⁸ depict the variability of orbital ENSO mean state. (e) The stacked benthic δ¹⁸O record⁴⁹. Numbers at the top indicate MISs. Arrows depict an increase of the AM and the SAM. The typical SAM record from southern Brazil follows ASI and thus displays a broad anti-phase relationship to the AM. In contrast, while the record from western Amazonia tracks ASI during relatively warm periods (MIS 1, 5 and 7) when sea level was higher, it shows an apparently anti-phase relationship to some extent to ASI during relatively cold periods (MIS 2–4 and 6) when sea level was lower (see Supplementary Fig. S11 for more details). To first order, the ENSO counterbalances and reinforces orbital SAM variations in western Amazonia and eastern Amazonia-northeastern-southern Brazil, respectively (see Supplementary Figs S9 and S10 for details).