Original abstract: We calculated the distributed surface mass and energy balance of Shallap Glacier, Cordillera Blanca, Peru (9° S, 77° W, 4700–5700 m a.s.l., ~ 7 km2), on hourly time steps for two years (September 2006–August 2008) using a process-based model and meteorological measurements as input. Model parameter combinations were optimized against 21 temporal readings of 20 stakes in the ablation zone of the glacier. Uncertainty caused by model input parameters and parameterization schemes was estimated using a leave-one out cross-validation scheme, which yields values of root mean square deviation (RMSD) of surface height change < 1 m (< 10% of the measured amplitude) for all stakes. With the best parameter combination (smallest RMSD) applied, the modeled annual surface mass balance of the glacier was -0.32 ± 0.4 m w.e. (water equivalent) for September 2006–August 2007 and...

Original abstract: We explore the small-scale spatial and temporal transferability of model parameters between two points in the ablation zone of tropical Glaciar Shallap, Cordillera Blanca, Peru (9°S, -77° W; ~4800 m a.s.l.) in order to provide a robust assessment of the performance of a process-based glacier mass-balance model. Relative surface height change is calculated at hourly time-steps, and cumulative values are compared to surface height measurements made at irregular intervals (14–64 days) over the course of two continuous hydrological years (August 2006–August 2008). Best-performing parameter combinations were determined for each point from the outcome of 1000 model simulations for which parameters were varied randomly within a defined range. With these parameter combinations measurements for a specific location and time-span are well reproduced. Transferring the parame...

Field and modelling based research indicates that for tropical glaciers, variations in snow cover and the altitude of the snow line via albedo effects are among the most crucial factors to explain the differences in annual glacier mass balance variability. It is therefore essential to identify the height of the phase change during precipitation events and its coupling with glacier mass balance. This knowledge is also fundamental to assess possible future impacts of e.g. changing air temperatures on glacier mass balances at low latitudes. However, the knowledge on heights of phase changes and air temperature during precipitation events is severely limited by the small number of meteorological measurements at high altitudes in the tropics and the Himalaya. Additionally, their one-dimensional type of observation that cannot appropriately account for the variations along the vertical dimensi...

In Peru, about 50% of the energy is produced from hydropower plants. An important amount of this energy is produced with water from glaciated catchments. In these catchments river streamflow is furthermore needed for other socio-economic activities such as agriculture. However, the amount and seasonality of water from glacial melt is expected to undergo strong changes. As glaciers are projected to further decline with continued warming, runoff will become more and more sensitive to possible changes in precipitation patterns. Moreover, as stated by a recent study (Neukom et al., 2015), wet season precipitation sums in the Central Andes could decrease up to 19-33 % by the end of the 21st century compared to present-day conditions. Here, we investigate future runoff availability for selected glacierized catchments in the Peruvian Andes. In a first step, we apply a simplified energy balance ...

Peruvian glaciers are important contributors to dry season runoff for agriculture and hydropower, but they are at risk of disappearing due to climate warming. Their energy balance and ablation characteristics have previously been studied only for individual glaciers, with no comparisons between regions. We applied the physically-based, energy balance melt component of the model Tethys-Chloris at five on-glacier meteorological stations: three in the Cordillera Blanca near Huaraz (with glaciers above ~4300 m a.s.l.), and two in the Cordillera Vilcanota east of Cusco (with glaciers above ~ 4800 m). The climate of these regions is strongly seasonal, with an austral summer wet season and winter dry season. Our results revealed that at most sites the energy available for melt is greatest in the wet season. This is a consequence of the dry season energy losses from the latent heat flux and net ...