Glacier Variations and Their Causes in the Northern Patagonia Icefield, Chile, Since 1944

The variations of six outlet glaciers of the northern Patagonia icefield were investigated. utilizing aerial photographs taken in 1944/45, 1974/75, and 1983/84, and were compared with the climatic trend. Between 1944 and 1984, a maximum recession of around 2.5 km was observed at two calving glaciers, while no variation occurred at one glacier. Three patterns of variations were recognized: (1) fairly constant recession during the last 40 yr (two glaciers); (2) rapid retreat during the 1974-1984 period (two glaciers); and (3) rapid retreat between 1944 and 1958. The amount of the surface lowering ranges from 40 to 120 m during the last 40 yr. These retreat and surface lowering rates are generally comparable to those reported for glaciers in other regions. The temperature and precipitation data recorded at a nearby station do not show any definite trends which can explain the general glacier variations elucidated in this study, suggesting strong local variation of the snow accumulation and effect of the relative height of the rock threshold on ice spilling.