RECESSION OF YANAMAREY GLACIER IN CORDILLERA-BLANCA, PERU, DURING THE 20TH-CENTURY

For Yanamarey Glacier in Cordillera Blanca, Peru, mostly situated between about 5000 and 4600 m, maps of the surface topography at a scale of 1:5000 obtained by terrestrial triangulation for 1973, 1982 and 1988 and by aerial photogrammetry for 1948 and 1962 are compared with the glacier boundaries from a 1939 map and an undated maximum extent inferred from moraine morphology. The glacier length decreased from the maximum, 2800 m to 1600 m in 1948 and to 1250 m in 1988, with an accompanying decrease in area from 17 x 10(5) to 10 x 10(5) and thence to 8 x 10(5) m(2). The shrinkage of ice volume was 35 x 10(6) m(3) from the maximum to 1948, and 29 x 10(6) m(3) from 1948 to 1988; compared to a total remaining ice volume of about 25 x 10(6) m(3) in 1988. This quantitative assessment of mass-loss rates creates the observational basis for sensitivity studies of the climatic forcing.