INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
Long-term glacier variations in the Central Andes of Argentina and Chile, inferred from historical records and tree-ring reconstructed precipitation
CARLOS LE QUESNEA,*, CESAR ACUÑA, JOSÉ A. BONINSEGNA , ANDRÉS RIVERA, AND JONATHAN BARICHIVICH
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
Lugar: Amstedam; Año: 2007 p. 1 - 1
Snow and ice in the Central Andes of Argentina and Chile (33-36ºS) are the main water reservoir for the highly populated regions near the cities of Santiago and Mendoza. The glaciers of this region have retreated and shrinkage in recent decades, presumably in response to atmospheric warming and precipitation decrease. The atmospheric warming in Central Chile is significant, and partially explained by the 1976 jump. However, the precipitation decrease is not significant for the last 70 years especially in Santiago, but in the long term scale (centennial) several long instrumental records (including Santiago) are showing a decrease trend influenced by a wet spell at the end of the 19th century. In recent decades several wet extreme years have occurred in connection to the warm phase of El Niño Southern Oscillation (ENSO) events. In response to these climatic trends, glaciers have experienced positive mass balances during El Niño years, although in a long term most of them have experienced mass losses. Snow and glacier melting are the main runoff source during dry summers in this region, therefore the reduction of ice surfaces and the increase in altitude of the snowline during recent decades are possibly jeopardizing water supply. In order to provide a long term perspective of glacier fluctuations and their relationship with climatic variability, historical glacier variations were reconstructed and lately compared to a tree-ring based precipitation reconstruction. A multi proxy approach was used (historical documents, old aerial photographs and satellite imagery) to reconstruct glaciers fluctuations, being Glacier Cipreses the longest and largest retreat record in central Chile with data from AD 1842. A 712-year precipitation reconstruction from Santiago de Chile (33° 26´ S / long. 70° 41´ W, 520 m asl) was obtained, which is characterized by a centennial variability with marked dry conditions around years 1440 AD and 1600 AD, whilst wet conditions were detected around years 1500 AD, 1650 and 1850 AD, since this maximum, the reconstructed series is showing a clear secular decrease trend. The reduction in precipitation indicated by this reconstruction for the last 150 years, together with the significant warming experienced in Central Chile, are explaining the documented regional glacier retreat. Some glacier advances observed during historical times have been associated to surging events, therefore are considered anomalies within a general shrinkage trend.