Past African dust inputs in Western Mediterranean area controlled by the complex interaction between ITCZ, NAO and TSI

Abstract

Abstract. North Africa is the largest source of mineral dust on Earth, which has multiple impacts on the climate system; however, our understanding of decadal to centennial changes in African dust emissions over the last few millennia is limited. Here, we present a high-resolution multiproxy analysis of sediment core from high-elevation lake Bastani, in Corsica Island to reconstruct past African dust inputs to the Western Mediterranean area over the last 3150 yrs cal BP. Clay Mineralogy and geochemical data allows us to identify that terrigenous fluxes are almost exclusively related to atmospheric dust deposition from the West and North Sahara over this period, which is consistent with current observations. High resolution geochemical contents provide a reliable proxy of Saharan dust inputs with millennial to centennial scale variations. Millennial variations have been correlated to the long term southward migration of the Intertropical Convergence Zone (ITCZ) with an increase of dust input since 1070 yrs cal BP. This correlation suggests a strong link with ITCZ and could reflect the increased availability of dust sources to be mobilized with an increase in wind and a decrease in precipitation over West and North Africa. For centennial to decadal variations, wavelet analyses show that since 1070 yr cal BP, NAO is the main climatic forcing with an increase of Saharan dust input during positive phase, as suggested by previous study over the last decades. However, when ITCZ is in a northern position, before 1070 yr cal BP, wavelet analyses indicate that total solar irradiance (TSI) is the main forcing factor, with an increase of African dust input during low TSI. With climate reanalysis over the instrumental era, during low TSI we observe a significant negative anomaly in pressure over Africa which is known to increase the dust transport. These two climatic forcing factors (NAO, TSI) modulate Saharan dust inputs to the Mediterranean area at centennial timescale through changes in wind and transport pathways.