This study uses stable isotopes and major ions to examine the seasonal evolution of penitentes on the surface of Tapado Glacier, in the Norte Chico region of the Chilean Andes. A snow pit was sampled in November 2011, and penitentes were sampled during the summer (December 2011 and January 2012). The major ion load of the winter snowpack is dominated by Ca2+ (60%), SO42- (16%) and NO3- (13%), and there is little influence from marine air masses at the site, with most SO42-, Mg2+, Ca2+ and Na+, derived from non-sea salt sources. During the early ablation season we observe increases in stable isotope ratios and major ion concentrations (particularly lithic ions Na+, Mg2+ and Ca2+) in the upper reaches of penitentes, which is attributed to sublimation and the aeolian deposition of dust particles. In the late-summer, melt replaces sublimation as the dominant ablation process and results in smoothing of the stable isotope profile and the elution of major ions within the penitente snow and ice matrix. Copyright (C) 2015 John Wiley & Sons, Ltd.