Changes in the Red Sea Overturning Circulation during Marine Isotope Stage 3

Abstract. The oceanography of the Red Sea is controlled by the restricted exchange of water masses with the Indian Ocean and by high evaporation rates due to the arid climate of the surrounding land areas. In the northern Red Sea, the formation of oxygen-rich subsurface waters ventilates the deeper parts of the basin, but little is known about the variability of this process in the past. The stable oxygen and carbon isotope records of epibenthic foraminifera from a sediment core of the central Red Sea allow for the reconstruction of changes in the Red Sea Overturning Circulation (ROC) during Marine Isotope Stage 3. The isotope records imply millennial-scale variations in the ROC, in phase with climate variability of the high northern latitudes. This suggests an immediate response of dense water formation to the regional climate and hydrology of the northern Red Sea. The ROC was intensified under hyper-arid conditions during Heinrich stadials and was diminished during Dansgaard-Oeschger interstadials. While these changes are reflected in both stable oxygen and carbon isotope records, the latter data also exhibit changes in phase with the African-Indian monsoon system. The decoupling of the stable carbon and oxygen isotope records at the summer monsoon maximum centred around 55–60 ka B.P. may be associated with an increased inflow of nutrient-rich intermediate waters from the Arabian Sea to the central Red Sea. This process fuelled local surface-water productivity resulting in enhanced remineralization of sinking organic matter and release of ¹²C at intermediate water depths.