African monsoon enhancement during the penultimate glacial period (MIS 6.5 ∼ 170 ka) and its atmospheric impact

Online Access: Get full text
doi: 10.1029/2008PA001630
Author(s): Tisserand, Amandine; Malaizé, Bruno; Jullien, Elsa; Zaragosi, Sébastien; Charlier, Karine; Grousset, Francis
Author Affiliation(s): Primary:
Université Bordeaux I, Environnements et Paléoenvironnements Océaniques, Talence, France
Volume Title: Paleoceanography
Source: Paleoceanography, 24(2). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 82 refs.; illus., incl. sketch maps
Summary: A reconstruction of northwest African summer monsoon strength during the cold marine isotopic stage (MIS) 6 indicates a link to the seasonal migration of the Intertropical Convergence Zone (ITCZ). High-resolution studies of eolian dust supply and sea surface temperature recorded in marine core MD03-2705, on the Mauritanian margin, provide a better understanding about the penultimate glacial history of northwestern African aridity/humidity and upwelling coastal activity. Today, site MD03-2705 experiences increased upwelling and dust flux during the winter months, when the ITCZ is in a southerly position. Analyses of foraminifera isotopic composition suggest that during MIS 6.5 (180-168 ka) the average position of the ITCZ migrated north, marked by an increase in the strength of the summer monsoon, which decreased eolian dust transport and the coastal upwelling activity. The northward migration is in phase with a specific orbital combination of a low precessional index with a high obliquity signal. High-resolution analysis of stable isotopes (δ18O and δ13C) and microscale resolution geochemical (Ti/Al and quartz grain counts) determinations reveal that the transition between monsoonal humid (MIS 6.5) and dry (MIS 6.4) conditions has occurred in less than 1.3 ka. Such rapid changes suggest a nonlinear link between the African monsoonal rainfall system and environmental changes over the continent. This study provides new insights about the influence of vegetation and oceanic temperature feedbacks on the onset of African summer monsoon and demonstrates that, during the penultimate glacial period, changes in tropical dynamics had regional and global impacts.
Year of Publication: 2009
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 24 Surficial Geology, Quaternary Geology; Africa; Atlantic Ocean; Atmospheric transport; Cenozoic; Clastic sediments; Cores; Dust; Foraminifera; Invertebrata; Isotope ratios; Isotopes; Leg 108; MIS 6; Marine sediments; Microfossils; Monsoons; North Atlantic; Northeast Atlantic; O-18/O-16; ODP Site 658; Ocean Drilling Program; Ocean circulation; Oxygen; Paleoclimatology; Petrography; Pleistocene; Protista; Quaternary; Sediments; Stable isotopes; Transport; Upper Pleistocene
Coordinates: N204457 N204457 W0183451 W0183451
N180500 N180500 W0210900 W0210900
Record ID: 2010081653
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States