Open AccessAfrican monsoon enhancement during the penultimate glacial period (MIS 6.5 ∼ 170 ka) and its atmospheric impact
Author(s) -
Tisserand Amandine,
Malaizé Bruno,
Jullien Elsa,
Zaragosi Sébastien,
Charlier Karine,
Grousset Francis
Publication year - 2009
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2008pa001630
Subject(s) - intertropical convergence zone , upwelling , geology , monsoon , foraminifera , climatology , oceanography , glacial period , aeolian processes , east asian monsoon , last glacial maximum , sea surface temperature , holocene , precipitation , benthic zone , geomorphology , geography , meteorology
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 ( δ 18 O and δ 13 C) 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.