Mountain glacier systems are decreasing in volume worldwide yet relatively little is known about their upper reaches (>5000 m). Here we show, based on the world’s highest ice core and highest automatic weather stations, the significant and increasing role that melting and sublimation have on the mass loss of even Mt. Everest’s highest glacier (South Col Glacier, 8020 m). Estimated contemporary thinning rates approaching ~2 m a⁻¹water equivalent (w.e.) indicate several decades of accumulation may be lost on an annual basis now that glacier ice has been exposed. These results identify extreme sensitivity to glacier surface type for high altitude Himalayan ice masses and forewarn of rapidly emerging impacts as Mt. Everest’s highest glacier appears destined for rapid retreat.

Peruvian glaciers are important contributors to dry season runoff for agriculture and hydropower, but they are at risk of disappearing due to climate change. We applied a physically based, energy balance melt model at five on‐glacier sites within the Peruvian Cordilleras Blanca and Vilcanota. Net shortwave radiation dominates the energy balance, and despite this flux being higher in the dry season, melt rates are lower due to losses from net longwave radiation and the latent heat flux. The sensible heat flux is a relatively small contributor to melt energy. At three of the sites the wet season snowpack was discontinuous, forming and melting within a daily to weekly timescale, and resulting in highly variable melt rates closely related to precipitation dynamics. Cold air temperatures due to a strong La Niña year at Shallap Glacier (Cordillera Blanca) resulted in a continuous wet season snowpack, significantly reducing wet season ablation. Sublimation was most important at the highest site in the accumulation zone of the Quelccaya Ice Cap (Cordillera Vilcanota), accounting for 81% of ablation, compared to 2%–4% for the other sites. Air temperature and precipitation inputs were perturbed to investigate the climate sensitivity of the five glaciers. At the lower sites warmer air temperatures resulted in a switch from snowfall to rain, so that ablation was increased via the decrease in albedo and increase in net shortwave radiation. At the top of Quelccaya Ice Cap warming caused melting to replace sublimation so that ablation increased nonlinearly with air temperature.

The Cordillera Vilcanota in the southern Peruvian Andes has been the site of significant research focused on paleoclimatic reconstructions from ice cores (Quelccaya), past glaciations, climate–glacier interactions, and ecological and human responses to climate change. In this article, we analyse precipitation patterns in the region from 2004 to 2010 using twice daily precipitation observations from six regional climate stations and hourly observations of precipitation intensity from nearby Cusco International Airport. We also analyse atmospheric fields of temperature, wind, and moisture at 700 and 200 hPa from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset and create 72-h antecedent upstream air trajectories for the heaviest precipitation events using the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Results indicate that the majority of annual precipitation across the cordilleras and inter-montane valleys alike occurs from nocturnal, regionally coherent rainfall events, inferred to be stratiform in structure, that occur in association with deep moist convection over adjacent Amazon lowlands. Low-level moisture (as inferred from the antecedent upstream air trajectories) for precipitation events can be supplied from a number of different regions, including from the northwest and west. The trajectory analysis reveals a strong dominance (83%) of precipitation events occur under weak flow regimes from nearby Amazon basin source regions, with 50% associated with trajectories from the northwest. In addition, the El Niño-Southern Oscillation (ENSO) signal reported in previous work in the central Andes is not necessarily representative of the Cordillera Vilcanota, where La Niña years (including 2007–2008) typically experience slightly below normal precipitation and El Niño years (including 2009–2010) are considerably wetter. These results are of particular value in understanding atmospheric signals registered in Andean low latitude ice cores, and point the way towards obtaining greater climatological inference from parameters preserved in annual snow and ice stratigraphy. Copyright © 2013 Royal Meteorological Society