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

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

Barcelona, España

Congreso; 4th International Limnogeology Congress (ILIC2007), “Limnogeology: tales of an evolving Earth”; 2007

Paleoenvironmental research in South American extratropics suggests that an integrated network of archives is essential to better define regional climate reconstructions. The analyses of long-term hydro-climatological series are crucial to calibrate proxy climate archives for improving reconstructions of past Earth-system interactions at middle latitudes. During the last century, SE South America has experienced important changes in its precipitation regime, consequently affecting the hydrologic balance. Hydroclimatic records across central Argentina show contrasting balances during the last 110 years. The lake level records of Laguna Mar Chiquita (30°E, 62°W), Laguna Melincué (33°E, 61°W) and Lagunas Encadenadas del Oeste (LEO) (37°E, 62°W), highlight the sensitivity of these closed lakes to temporal hydrological unevenness. Rainfall analysis and lake-water levels reveal: a) a significant positive trend in the annual rainfall during the 20th century, b) the annual distribution of rainfall is irregular, with precipitation mostly occurring during  the austral summer, c) high annual precipitations and thus comparatively higher lake levels, during 1914, 1915, 1919 and 1923; d) a long dry interval and extremely low lake levels with high water salinities from 1930 to 1970, including a hydrological reverse during the late 50´s and early 60´s, and e) an outstanding humid span since the 70´s that triggered pervasive lakes levels increases synchronous with higher discharges in the Río de la Plata basin (See Sylvestre et al., this volume).The geographical position of the LEO at the transition zone between the Pampean Plains and Patagonia highlights the potential of this site for estimating and unravel the mechanisms behind the most recent and past climate variability. Several forcing factors control the moisture transport variability from the tropics into the middle latitudes. Ongoing limnogeological studies across the Pampas may help to disentangle the mechanisms behind changes in the meridional atmospheric circulation in South America. In particular, the limnogeological 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 South American Arid Diagonal