The South American summer monsoon during the Holocene

CRISTIANO M. CHIESSI; STEFAN MULITZA; DAVID HESLOP ; EDUARDO PIOVANO; MATHIAS VUILLE ; SEBASTIAN RAZIK

mendoza

Congreso; 18ISC - Sedimentology at the Foot of the Andes; 2010

Southeastern South America is the most densely populated and agriculturally productive region of the continent, greatly relying on South American Summer Monsoon (SASM) precipitation. A comprehensive understanding of the SASM activity on different time scales is thus a key issue. Here we explore the main forcing factors controlling SASM behavior during the Holocene using a ca. 14-ka-long marine sediment core from the continental slope off southeastern South America. The Fe/K and Al/Si ratios of terrigenous sediments delivered to our core site accurately reflect the intensity of chemical weathering and consequently SASM precipitation over southern (sub)tropical South America. Our data show that until ca. 8 ka B.P. SASM variability was strongly linked to Northern Hemisphere climate and to changes in Atlantic meridional overturning circulation strength. Two wet periods (i.e., Younger Dryas and between 10.3 and 8 ka B.P.) highlight that remnant glacial boundary conditions still performed a great influence on southern tropical climate. After ca. 8 ka B.P., subtropical summer insolation controlled SASM intensity that was characterized by a dry mid Holocene and a wet late Holocene.