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Oct 17, 2022
Hydroclimate and ENSO Variability recorded by oxygen isotopes from tree rings in the South American Altiplano
Hydroclimate and ENSO Variability recorded by oxygen isotopes from tree rings in the South American Altiplano

Figure 1: Relationships between Polylepis tarapacana δ18OTR chronologies (sorted from the northernmost to the southernmost form top to bottom) and precipitation (a) Pearson correlation coefficients between δ18OTR and monthly regional precipitation based on meteorological stations (note that left y axis is inverted) for August of the previous growing season (lowercase) to May of the current growing season (uppercase) for 1950–2007. Vertical solid (dashed) lines represent significant (nonsignificant) bootstrap monthly correlation coefficients (alpha<0.05). Blue shading shows CHIRPS precipitation seasonality (1981–2020). Green vertical shading highlights current-year JFM (b) δ18OTR values during years of extreme (upper and lower percentiles [25%]) JFM precipitation. Asterisks indicate significant differences (Mann-Whitney, alpha <0.05) (c) Field Spearman correlations between the δ18OTR chronologies and JFM CRU precipitation; only significant values are shown (alpha <0.05).

Hydroclimate variability in tropical South America is strongly regulated by the South American Summer Monsoon (SASM). However, past precipitation changes are poorly constrained due to limited observations and high-resolution paleoproxies. We found that summer precipitation and the El Nino-Southern Oscillation (ENSO) variability are well registered in tree-ring stable oxygen isotopes (δ18OTR) of Polylepis tarapacana in the Chilean and Bolivian Altiplano in the Central Andes (18–22°S, ∼4,500 m a.s.l.) with the northern forests having the strongest climate signal (Figure 1). More enriched δ18OTR values were found at the southern sites likely due to the increasing aridity toward the southwest of the Altiplano. The climate signal of P. tarapacana δ18OTR is the combined result of moisture transported from the Amazon Basin, modulated by the SASM, ENSO, and local evaporation, and emerges as a novel tree-ring climate proxy for the southern tropical Andes.

Référence : Rodriguez-Caton M., Andreu-Hayles L., Daux V., Vuille M., Varuolo-Clarke A., Oelkers R., Christie D.A., D’Arrigo R., Morales M., Rao M.P., Srur A., Vimeux F., Villalba R. Hydroclimate and ENSO Variability recorded by oxygen isotopes from tree rings in the South American Altiplano. Geophys. Res. Lett. 49, e2021GL0958

 

 
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