Relations between the oxygen isotope ratios in the Nevado Illimani (Bolivia) snow and ice with the precipitation temporal variability over South America

Abstract

This article examines the temporal relations between the oxygen stable isotopes ratio (^δ18O) in an ice core from the Nevado Illimani, Bolivia (16°37’S, 67°46’W), with precipitation series from South America. We used δ¹⁸O data from the upper 50 m of this core and precipitation monthly totals collected at 890 weather stations in South America in the period 1979–2008. Precipitation data were arranged in a grid with ~2° latitude and longitude resolution, for zoning the spatial temporal variability, using the Principal Components Analysis Mode–S. The relation between the δ¹⁸O record with drought and rain events above the South America mean values changes seasonally due to spatial migration of transport mechanisms and moisture convergence. The precipitation interannual temporal variability in the equatorial and subtropical regions is the one with the greatest similarity to δ¹⁸O variations in the Nevado Illimani. This relationship results from the control of precipitation anomalies in the two regions by the surface temperature of the equatorial Pacific and North Atlantic oceans, at temporal frequencies from 24 to 60 months. The δ¹⁸O and precipitation series have temporal cycles of high spectral frequency that vary independently, as those cycles are controlled by local factors.