The tropical rain belt of South America during Plio-Pleistocene cooling

• Applicant: Dr. Lydie Madeleine Dupont
• Subject Area: Palaeontology
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 260717210

The proposal focusses on the timing of the atmospheric circulation intensification and the position of the Intertropical Convergence Zone (ITCZ) over South America during the Pliocene. Pliocene cooling involves the intensification of the atmospheric circulation related to temperature changes in the Equatorial Pacific Ocean. Pliocene sea surface temperature (SST) records of the Pacific indicate that increases of the zonal and meridional SST gradients intensified the atmospheric Walker and Hadley circulations, respectively. Restriction of the surface water exchange between the Atlantic and Pacific oceans recorded by the salinity divergence between oceans indicates that the final closure of the Central American Seaway (CAS) occurred between 4.7 and 4.2 Ma. The closure had a strong impact on the circulation in the Equatorial Pacific and the development of the eastern Equatorial Pacific cold tongue. Closure of the CAS also influenced the latitudinal position of the ITCZ, but models and data indicate shifts in opposite directions. The proposal aims at a palynological record of Pliocene vegetation change in west equatorial South America and the western Andean Cordillera for three key periods of the Pliocene using marine sediments of ODP Site 1239 offshore of Ecuador. We aim at a record of changes in climate and terrestrial hydrology of northwest South America related to an early shift of the ITCZ between 4.7 and 4.2 and the timing of the intensification of the Walker circulation between 3.6 and 1.7 Ma. In the first year we approached the early Pliocene period. We could demonstrate that the ITCZ shifted southwards in line with the data confirming the hypothesis of its southward shift during CAS closure.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 527: Bereich Infrastruktur - "International Ocean Discovery Program" (IODP)
• International Connection: Colombia, Netherlands
• Co-Investigator: Professor Dr. Gerold Wefer
• Cooperation Partners: Professor Dr. Hermann Behling; Professorin Dr. Catalina González; Professor Dr. Jeroen Groeneveld; Professor Dr. Henry Hooghiemstra; Dr. Frank Lamy; Dr. Daniel Rincón; Professor Dr. Ralf Tiedemann