David Clark, Nicholas Barrand

The glaciers of the tropical Andes have been observed to be losing mass for much of the last century. These changes are both driven by, and an indicator of global climate change. These glaciers are important as they represent a crucial water source for downstream communities, supplying agriculture, urban usage, industry, mining and hydropower. This study aims to quantify glacial mass loss for the Cordillera Blanca and Cordillera Huaytapallana for the period 1972-2018, as well as identify potential meteorological drivers of these changes in order to extend the mass balance record back in time and understand the long-term regional causes of glacial recession. In order to do this Landsat imagery is used to identify glaciers, alongside repeat DEMs derived from satellite altimetry and historic maps. DEMS are used to measure glacier surface elevation changes and calculate mass balance. Comparisons with time-series of meteorological data are conducted to identify potential forcing factors of glacial mass balance. The results of this study show that the glaciers of CB (-0.45 ± 0.08 m yr 1 w.e) and CH (-0.48±0.12 m yr 1 w.e) have undergone substantial mass loss over the last 50 years. Variations in mass balance are observed based on glacier aspect and elevation, as well as over the different time periods studied. Meteorological analysis identifies precipitation phase and humidity to be the main forcing factors of Cordillera Blanca mass balance, with air temperature and precipitation phase important for the Cordillera Huaytapallana.