Hydroclimate variability in southern South America since the LGM

PIOVANO, E.; ARIZTEGUI, D.; SYLVESTRE, F.; CÓRDOBA, F.; CIOCCALE, M.

Corvallis

Congreso; 3rd Open Science Meeting, PAGES, "Retrospective views on our planet's future"; 2009

PAGES

Paleoenvironmental investigations in South America have recently shown the advantage of analyzing past climate variability from a regional prospective (e.g., LOTRED-SA program). Early efforts led by the PAGES-sponsored initiative PEP-I triggered a substantial increase in limnogeological studies, as shown by several presently running research programs. Within this framework, the study of paleoenvironmental records across the subtropical Pampean plains of southern South America (SSA) south of the Tropic of Capricorn and east of the Andes is critical. These archives allow us to compare for the first time latitudinal paleocirculation dynamics and to picture their hydroclimatic response since the Late Pleistocene. These paleoenvironmental reconstructions further high light the development of contrasting hydrological patterns between the Pampas and Patagonia at both sides of the South American Arid Diagonal (AD). Numerous paleohydrological archives indicate dominant wet conditions during cold phases such as those that occurred during the middle Holocene or the Little Ice Age in Patagonia or even the Central Andes, with a dominant Pacific source of moisture. During the same time interval, contrasting dry conditions prevailed across the subtropical low-lands east and north of the AD with an Atlantic-dominated source of moisture. Conversely, extensive dryness across Patagonia and wet conditions in the Pampas can be inferred during warm climatic phases such as the Medieval Climatic Anomaly or the last part of the 20th century. This antiphasing hydrological scenario developed after the mid-Holocene, coinciding with an intensification of the Southern Westerlies along with a weakened monsoonal circulation. Hence, our results show that paleolimnological studies in the subtropical plains of South America are critical for obtaining realistic regional reconstructions of past climate variability. The PALEO-PAMPAS initiative is designed to disentangle the role of the subtropics to understand past atmospheric circulation changes in South America.