The 20th century limnological and rainfall variation across the Pampean plains of central Argentina.

CÓRDOBA, F, PIOVANO, E., PASQUINI A. I

. Malargüe, Mendoza, Argentina

Simposio; Reconstrucciones regionales de las variaciones climáticas en América del Sur durante el Holoceno tardío: una nueva iniciativa de PAGES; 2006

Paleoenvironmental research in South American extratropics suggests that an integrated network of archives is essential to define regional climate reconstructions. The analyses of long-term hydro-climatological series are crucial to calibrate proxy climate archives for an improved reconstruction of past Earth-system interactions at middle latitudes. Hydroclimatic records across central Argentina, show contrasting hydrological balances during the last 110 years. The 20th century lake level records of Laguna Mar Chiquita (30°E, 62°W), Laguna Melincue (33°E, 61°W) and Lagunas Encadenadas del Oeste (LEO) (37°E, 62°W), highlight the sensitivity of these lakes to temporal hydrological unevenness. Rainfall analysis and lake-water levels during the 20th century reveal: a) high annual precipitations and thus comparatively higher lake levels during 1914, 1915, 1919 and 1923; b) a long dry interval and extremely low lake levels from 1930 to 1970, including a hydrological reverse during the late 50´s and early 60´s, and c) an outstanding humid phase since the 70´s that triggered pervasive lake level increases across the Pampean region, synchronous with changes in the Río de la Plata basin. Both, the dry and wet phases have profoundly disrupted social activities in the region. Further studies on the limnogeologeological record the pampean lakes will offer the opportunity to improve the understanding of past changes in the meridional atmospheric circulation. In particular, the climate archive of LEO will provide important clues on the past monsoonal activity at its southernmost influence and a better definition of the antiphased hydrological balance that is present at both sides of the Arid Diagonal.