Modern mineral dust depositions in East Antarctica: faithful geochemical tracers of Southern Africa dust contributions and evolution of the climate during the Holocene

Abstract

Natural mineral dust are composed of reactive species affecting directly or indirectly the global climate through aerosol-radiation-cloud-chemistry interactions. They are also efficient suppliers of organic or inorganic components that can influence the primary productivity in oceans, such as the Austral Ocean.The present study attempts to solve the puzzle of the origin (the potential source areas - PSA) of dust deposition in East Antarctica (EA). We combine analyses of size, shape, mineralogy, geochemistry (trace element, and especially REE data), as well as strontium (Sr), neodymium (Nd) and lead (Pb) isotopes, performed on modern snow dust samples collected along a ~200km transect in the Dronning Maud Land area (from the Belgian Station Princess Elisabeth Antarctica to the coast). A statistical mixing model was specifically developed to fit the Rare Earth Elements (REE) patterns of Antarctic dust samples (Vanderstraeten et al., 2023) by combining REE profiles from PSA in Southern South America (Patagonia, Puna-Altiplano plateau), Southern Africa (Namibia, SAF), Australia and New-Zealand. In addition to REE, PSA isotopic compositions of Sr, Nd and Pb were analysed (Gili et al., 2022), specifically in 30 samples from the Namibian coast where an evident lack of analyzed samples was detected in the literature data collection.The atmospheric particles mainly show a submicronic size (> 98% of particles < 5μm, n=2500) and angular shape. SEM-EDS observations suggest spatial variations in mineralogy, reflecting the influence of input from the local Sør Rondanes mountains for the inland sites (Fe-Mg silicate > 50 %) and distal source’ input at the coast (predominance of aluminosilicates and quartz, with <20% of Fe-Mg silicates). The REE profiles and the Sr, Nd and Pb isotopic variability observed in present-day dust depositions at the EA coast, as it was demonstrated for the Holocene interglacial depositions (at Vostok and EDC; Gili et al., 2022) in East Antarctica and the South Atlantic Ocean, can be related to the contributions of two main PSAs: Southern South America, dominated by the major contribution of Patagonia and important percentage of the Puna–Altiplano Plateau, in combination with Southern Africa in response to the plausible transport by the strong Berg Winds. This work presents an innovative and multi-proxy approach for the identification of potential dust source contributions in the Southern Hemisphere, and East Antarctica in particular, which provides major implications for the reconstruction of atmospheric circulation and implications on climate evolution. Vanderstraeten et al., (2023), Science of the Total Environment, 881, 163450; http://dx.doi.org/10.1016/j.scitotenv.2023.163450Gili et al., (2022), Nature Communications earth & environment, 3 :129 ; https://doi.org/10.1038/s43247-022-00464