Reconstruction of upwelling and productivity in the southern part of the Peru-Chile Current: A multi parameter approach

Abstract

Five sediment cores were investigated with the aim to reconstruct the present and past regional upwelling and productivity variations in the southern part of the Peru-Chile Current (PCC). Several parameters such as organic carbon, calcium carbonate, opal, isotopic and faunal composition of planktic foraminifera, and the siliceous plankton assemblage served as proxies for the production and sedimentation of organic matter. The observations reveal generally higher productivities during the last glacial compared to the Early and Middle Holocene. During the Late Holocene, productivity increased again regardless of the position of the investigated cores. In addition, the observed predominantly southward increase in paleoproductivity, as recorded under present-day conditions, points to the same driving mechanisms of productivity in the last 40,000 years. During the last glacial, however, significant discrepancies can be observed between the record at 33°S and other records further north. Highest productivities at 33°S occurred around the Last Glacial Maximum (LGM, 21,000 ± 1000 yr BP), whereas further north, the productivity was highest before and after the LGM, and decreased slightly during the LGM.The applied productivity proxies showed that next to latitudinal position and strength of the zonal systems, i.e. the Southern Westerlies and the Antarctic Circumpolar Current (ACC), other processes such as the strength of the South Pacific subtropical gyre, El Niño Southern Oscillation (ENSO) events, and the hemispheric thermal gradient have been strongly affecting the upwelling intensity and paleoproductivity in this region during the last 40,000 years. In addition, other episodic events such as flooding of the shelf during Termination I (18,000 10,000 yr BP), as well as humid phases onshore prior to the LGM and during Termination I, may have increased the nutrient supply into the upwelling area north of 33°S resulting in enhanced paleoproductivity.