Recent Oscillations of the San Quintin and San Rafael Glaciers, Patagonian Chile

Earlier reports, maps, aerial photographs, and tree-ring dates for moraines are used to investigate and compare the oscillations of the land-based San Quintin Glacier and the calving, tidewater San Rafael Glacier in Southern Chile. The findings show that these two very different outlet glaciers of the North Patagonian Icefield (NPI) have displayed similar trends of ice front retreat and advance since the end of ‘The Little Ice Age’. The similarities imply that these glaciers are chiefly controlled by common climatic factors. A review of the literature suggests that some of the earlier reported positions of the San Rafael Glacier may be in error, but all authors agree on the beginning of the recessional trend in the late nineteenth century. The retreat of the San Rafael Glacier stopped in 1991 and by 1993 the San Quintin glacier was advancing over vegetated ground. This study mapped the San Quintin Glacier moraines and dated them by dendrochronology. Twelve years were added to tree-ring counts for colonization and growth to core height. Dendrochronology is also used to provide minimum rates of ice surface downwasting. Investigation of records from the nearest weather station suggests that precipitation could be the main control of ice front oscillations, with a response time of 20 years. A comparison of records from other weather stations to the north and south shows that these glaciers lie in a highly sensitive area between two climatic regimes, with precipitation and temperature, at present, weakly reflecting northern rather than southern Patagonian weather patterns.