Climatic controls on central African hydrology during the past 20,000 years.
Past hydrological changes in Africa have been linked to various climatic processes, depending on region and timescale. Long-term precipitation changes in the regions of northern and southern Africa influenced by the monsoons are thought to have been governed by precessional variations in summer insolation. Conversely, short-term precipitation changes in the northern African tropics have been linked to North Atlantic sea surface temperature anomalies, affecting the northward extension of the Intertropical Convergence Zone and its associated rainbelt. Our knowledge of large-scale hydrological changes in equatorial Africa and their forcing factors is, however, limited. Here we analyse the isotopic composition of terrigenous plant lipids, extracted from a marine sediment core close to the Congo River mouth, in order to reconstruct past central African rainfall variations and compare this record to sea surface temperature changes in the South Atlantic Ocean. We find that central African precipitation during the past 20,000 years was mainly controlled by the difference in sea surface temperatures between the tropics and subtropics of the South Atlantic Ocean, whereas we find no evidence that changes in the position of the Intertropical Convergence Zone had a significant influence on the overall moisture availability in central Africa. We conclude that changes in ocean circulation, and hence sea surface temperature patterns, were important in modulating atmospheric moisture transport onto the central African continent.
Schefuss
Enno
E
DFG-Research Center Ocean Margins (RCOM) at the University of Bremen, Klagenfurter Strasse, 28359 Bremen, Germany. eschefuss@whoi.edu
Schouten
Stefan
S
Schneider
Ralph R
RR
D000349:Africa; D001267:Atlantic Ocean; D002980:Climate; D049690:History, Ancient; D006813:Humidity; D006859:Hydrogen / Q000378:metabolism; D008055:Lipids / Q000032:analysis / Q000737:chemistry; D010103:Oxygen Isotopes; D010933:Plankton / Q000737:chemistry / Q000378:metabolism; D018526:Plant Transpiration; D010944:Plants / Q000737:chemistry / Q000378:metabolism; D011891:Rain; D012623:Seawater / Q000032:analysis / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014329:Tropical Climate; D014872:Water Movements
D008055:Lipids; D010103:Oxygen Isotopes; D006859:Hydrogen