... The fluctuations in the Mercedario δ¹⁸O record are assumed to reflect variations in temperature during the different seasons. Thus, minima (more negative values) in the δ¹⁸O record are attributed to austral winter precipitation (June, July, August) and maxima to austral summer (December, January, February). Fluctuations of the concentration of major ions match with the δ¹⁸O record such that high concentrations coincide with high values of δ¹⁸O attributable to austral summer precipitation. All major ions show this behaviour as illustrated for SO²⁻₄ (see Figure) ... (Chapter 3.4)

Mercedario SO²⁻₄ concentration, δ¹⁸O record and suggested annual layers.