Glacier changes and climate trends derived from multiple sources in the data scarce Cordillera Vilcanota region, Southern Peruvian Andes

Abstract. The role of glaciers as temporal water reservoirs is particularly pronounced in the (outer) tropics because of the very distinct wet-dry seasons. Rapid glacier retreat caused by climatic changes is thus a major concern and decision makers demand urgently for regional/local glacier evolution trends, ice mass estimates and runoff assessments. However, in remote mountain areas, spatial and temporal data coverage is typically very scarce and this is further complicated by a high spatial and temporal variability in regions with complex topography. Here, we present an approach on how to deal with these constraints. For the Cordillera Vilcanota (Southern Peruvian Andes), which is the second largest glacierised Cordillera in Peru (after the Cordillera Blanca) and also comprises the Quelccaya Ice Cap, we assimilate a comprehensive multi-decadal collection of available glacier and climate data from multiple sources (satellite images, meteorological station data and climate Reanalysis), and analyze them for respective changes in glacier area and volume and related trends in air temperature, precipitation and specific humidity. In general, the climate data show a moderate (compared to other alpine regions) increase in air temperature, weak and not significant trends for precipitation sums, and an increase in specific humidity at the 500 hPa level. The latter is consistent with observed increase in water vapour at the tropopause level during the past decades. It is likely that the increase in specific humidity played a major role in the observed massive ice loss of the Cordillera Vilcanota over the past decades.