The 20th century hydroclimatic changes in central Argentina recorded in the sedimentary deposits of Laguna Melincué.

LUCÍA GUERRA; SANTIAGO PALAMEDI; EDUARDO PIOVANO

Mendoza

Congreso; 18th International Sedimentological Congress; 2010

International Asociation of Sedimentologists

Understanding the role played by the middle latitudes of Southeastern South America (SESA) during climate change situations has become a topic of growing interest among the scientific community. In this sense, the sedimentary record of Laguna Melincué (33°S-61°W), an alkaline shallow lake located in the Argentinean Pampean region, provides the opportunity to disentangle past and present hydroclimate variability across the subtropics of SESA. The instrumental and historical records of Laguna Melincué show important surface and water level fluctuations throughout the 20th century. Changing P-E ratios in this portion of SESA are ruled by the variability of the South America Monsoon like atmospheric circulation system. The high sensitivity and rapid response of Laguna Melincué in front of recent hydrological balance variability highlight the significance of its sedimentary record to analyze Holocene paleoeoclimates in SESA. The multiproxy analyses of sedimentary cores allow the recognition of alternating high lake-level facies (organic matter-rich), deposited during positive hydrological balances and low lake-level facies (carbonate-rich), indicative of negative balances. The hydrological reconstruction suggests an initial arid period during the first decades of the 20th century, followed by alternating humid and dry phases. A dramatic shift to wetter conditions (registered on both, sedimentary and instrumental records) started during the decade of 1970 and it is still present. When the last 100 years record of hydrological variability in Melincué is compared to other lake records across the Pampean region (e.g. Mar Chiquita, Lagunas Encadenadas) synchronous water level fluctuations are recognized. The observed in-phase hydrological behavior across the Pampas points toward the influence of the South America Monsoon on the last 100 years of hydrological changes and supports the hypothesis of this mechanism controlling Holocene hydroclimate variability in SESA.