Andean glacier mass balance through the last six decades

Meltwater from Andean glaciers sustains river flow heavily relied on by ecosystems and communities downstream, particularly during periods of drought. However, contemporary rates of glacier recession in the Andes are accelerating and the yield of freshwater from the high mountain environment here is forecast to decline in coming decades, increasing water stress in the region. Water resource management policies rely on robust hydrological and glacier modelling, which themselves require accurate, long-term records of glacier ice loss rates. Prior to the contemporary satellite era (2000-today), records of glacier mass balance are patchy in the Andes, with available data lacking temporal resolution or covering small glacier samples and our knowledge of glacier behaviour during this period can be improved. Here, we have assembled geodetic glacier mass balance records for 10 glacierised river catchments containing ~3200 glaciers and spanning different climatic zones between 9°S (Rio Santa) and 50°S (Rio Santa Cruz). We have generated glacier surface elevation change data using DEMs generated from regional aerial photography surveys, from three archives of declassified American spy satellite imagery (Corona KH4, Hexagon KH9 mapping camera and Hexagon KH9 panoramic camera) and from contemporary optical stereo archives (ASTER). Our geodetic time series captures considerable inter-catchment variability in glacier mass loss rates across different climatic zones, but clearly indicates accelerating glacier mass loss rates throughout the Andes since the 1960s. These results will be used to calibrate glacier and hydrological models which will simulate meltwater flux from the same 10 catchments towards 2150 as part of the NERC Highlights Project ‘Deplete and Retreat: the Future of Andean Water Towers’.