Oxygen stable isotopes in tree rings reveal 300 years of precipitation variability in the South American Altiplano.

MARIANO S. MORALES; ROSE OELKERS; ANA M. SRUR; VALERIE DAUX; MILAGROS RODRÍGUEZ-CATÓN; DUNCAN A. CHRISTIE; ARIANNA VARUOLO-CLARKE; MATHIAS VUILLE; RICARDO VILLALBA; LAIA ANDREU HAYLES; MUKUND PALAT RAO; FRANÇOISE VIMEUX; ROSANNE DARRIGO

New Orleans

Conferencia; AGU fall meeting; 2021

Polylepis tarapacana is the longest paleoclimatic tree-ring archive near the South American tropics. It grows up to 5200 m a.s.l. in the South American Altiplano, a semiarid-high elevation Andean Plateau. Ring-width annual records of P. tarapacana have provided centuries of past hydroclimate variability. Here, we developed a network of four oxygen stable isotope (18O) chronologies from P. tarapacana tree rings along the Altiplano (18S to 22S) for the period 1950-2010, with the southern site Uturunco (22.30 S 67.23 W, 4650 m a.s.l) spanning from 1700 to 2013 C.E. Our results revealed that P. tarapacana tree-ring 18O records January-March austral summer precipitation at all four sites. This season coincides with the pick of the South American Summer Monsoon (SASM), which drives most of the precipitation to this region. We also found that El Nino - Southern Oscillation (ENSO) variability is recorded by 18O, but better reflected at the northernmost location than at the southern sites. Overall, the signal of P. tarapacana 18O is the result of moisture coming from the Amazon Basin paced by the SASM and ENSO, as well as local evaporation. At site Uturunco we developed the first long-term 300 year tree-ring 18O chronology in tropical South America and have reconstructed precipitation variability since 1700 C.E. The 18O based tree-ring reconstruction explained more than 45% of the variance in precipitation. Our next step is developing multi-parametric tree-ring reconstructions combining ring-width and stable isotopes for a better understanding of the full range of climate variability of this region.