Tropical South American temperature responses to rapid high-latitude climate shifts since the last deglaciation

Reconstructing past temperature variations is essential for understanding climate systems and improve projections for future climate changes. In central-east South America, modern warming has been shown to progress faster than global average. Nonetheless, paleotemperature records remain sparse in central South America, which limits our ability to evaluate the response of this region to rapid shifts in global forcings, such as during the deglacial period. Studies show that temperature evolution during the deglaciation was characterized by high-latitude rapid warming episodes associated with major reorganizations of the Atlantic Meridional Overturning Circulation (AMOC), which led to perturbations in inter-hemispheric heat distribution. Yet, how these perturbations affect temperatures in tropical South America and the thermal evolution of this region is still largely unknown. Here we present a new 15k-year paleotemperature reconstruction from a precisely dated speleothem collected in central-eastern Brazil. The temperature record is based on the glycerol dialkyl glycerol tetraether (GDGT) paleothermometer, revealing a total of 6.1°C±0.81 (2std = 0.81°C) of temperature shifts over the last 15k years. Our findings provide evidence of a non-linear temperature increase since the last deglaciation with abrupt warming and cooling events in response to high-latitude forcings, shifts in South Atlantic sea-surface temperatures (SSTs), and increases in atmospheric CO₂. Finally, we present a temperature gradient within central-east Brazil and show how paleoclimate models might underestimate rapid temperature changes.