Glacier retreat and associated processes since the Last Glacial Maximum in the Lejiamayu valley, Peruvian Andes

Abstract

In this study, we examine glacier retreat and associated processes in the Lejiamayu valley, central Cordillera Blanca, Peru (9.27°S; 77.48°W) since the Last Glacial Maximum (LGM). Based on detailed mapping of well-preserved moraines, we reconstruct glacier extent during the LGM, the Antarctic Cold Reversal (ACR) and the Little Ice Age (LIA), being 21.34 km2 (LGM), 13.68 km2 (ACR) and 6.84 km2 (LIA). We document that glacier extent decreased to 2,86 km2 since the end of the LIA in this catchment (ice loss 58%). In addition, we explore the colonization and growth of lichens and Schmidt-hammer rock test R-values over the deglaciated surfaces, suggesting a relationship to possible evironmental controls rather than to the timing of the exposure. Further, we use empirical glacier velocity-based equation to estimate maximum potential future volume of the new glacial lake forming in the upper part of the valley (4725 m a.s.l.; 2.2 Mm3). We conclude that previous estimates of future lake volume might have been underestimated and that the sufficiency of the glacial lake outburst flood (GLOF) mitigation measures implemented at downstream located Lake Lejiacocha (4628 m a.s.l.) should be revised in future.