Revealing past climate variability using tree rings and stable isotopes from tropical and boreal regions in the Americas

High-resolution records of centennial climate variability are crucial considering the scarcity and overall short length of instrumental meteorological data in many regions of the world. The application of stable isotopic analysis in tree rings has emerged as a robust methodological tool for elucidating the intricate complexities of environmental history. This presentation will travel from high latitudes in North America to the Tropical Andes in South America to show how tree-ring stable isotopes can be used to reconstruct climate variability and atmospheric patterns across the Americas, as well as changes in Sea Surface Temperatures (SST). Stable oxygen isotopes (δ¹⁸O) measured in tree rings from white spruce trees from the Northwest Territories of Canada record similar large-scale climate patterns as modelled precipitation δ¹⁸O from a general circulation model (NASA GISS ModelE2 isotopically-equipped). Trees from the species Polylepis tarapacana growing at high elevation (~5,000 m a.s.l) at the South American Altiplano were used to reconstruct annual precipitation variability, which is driven by the South American Summer Monsoon, over the last 300 years. This newly developed tree-ring δ¹⁸O chronology revealed a robust hydroclimatic teleconnection showing interannual (2–5 years) and decadal (~11 years) periodicities consistent with records of Altiplano precipitation, central tropical Pacific SST, Andean ice core δ¹⁸O and tropical Pacific coral δ¹⁸O. Furthermore, new tree species of the genus Polyelpis growing in the inner tropics were discovered and found to have significant sensitivity to local and regional hydroclimate variability, showing a close link to tropical Pacific SST and El Niño–Southern Oscillation. Overall, our findings point out the importance of developing longer stable isotopes tree-ring records to overcome the inherent difficulties to reconstruct global hydroclimate variability.