Palaeoceanographic evolution of the central Red Sea during the late Holocene

Three multicores were studied in the Central Red Sea off Port Sudan at a W—E transect in order to reconstruct palaeoceanographic conditions of the past ~6000 years. Downcore fluctuations in the relative abundance of the epipelagic planktic foraminifera Globigerinoides ruber versus that of the deeper dweller G. sacculifer, together with the presence/absence pattern of the mesopelagic pteropod Limacina bulimoides, reflect variations in the mixed layer and intermediate water column properties and enabled a division of the past ~6000 years into five zones. These palaeoceanographic changes reflect late-Holocene climate fluctuations. Two distinct climate systems regulate the hydrography of the central Red Sea: the Mediterranean climate system to the north controls the formations of the deeper waters, at times of drier and harsher winters, with periods of increased abundance of G. sacculifer reflecting a vigorous deep-water formation in the northern Red Sea. The second is the monsoonal climate system that regulates the nutrient input from the south and the shifting northward position of the Intertropical Convergence Zone (ITCZ) at times of monsoon intensification. Increasing abundances in G. ruber indicate greater influence of the monsoonal climate system. The most arid interval (4200—3400 yr BP) is associated with high abundance of G. sacculifer and maximum abundance of Limacina bulimoides , linked to the Mediterranean climate system. This period is of a wide regional scale and also coincides with a pulse of weakening in the Indian Ocean monsoonal system.