Inverse Relationship of Marine Aerosol and Dust in Antarctic Ice with Fine-Grained Sediment in the South Atlantic Ocean: Implications for Sea-Ice Coverage and Wind Strength

Abstract

This research seeks to test the hypothesis that natural gamma radiation (NGR) from Ocean Drilling Program Site 1094, which displays variability over the last glacialinterglacial cycle similar to dust in the Vostok ice core, reflects fine-grained terrigenous sediment delivered by eolian processes. Grain size was measured on 400 samples spanning 0-20 m in a composite core. Accumulation of the <63µ size fraction at Site 1094 and dust in Vostok exhibit a negative correlation, suggesting the fine sediments are not dominantly eolian. However the technique used for grain size measurements cannot distinguish between terrigenous and biogenous materials; therefore it is possible much fine-grained material is diatoms. An inverse correlation between fine sediments and NGR supports this interpretation, and implies terrigenous materials were at times diluted by microfossils from high biological productivity. Fine marine sediments correlate positively with temperature and negatively with marine aerosol Na+ in Vostok. One plausible explanation is extensive sea-ice of cold intervals steepened ocean-continent temperature gradients, intensified winds, and led to increased transport of dust and marine aerosol to Antarctica yet also reduced biological productivity at Site 1094. Such a reduction despite increases in NGR, potentially representing Fe-rich dust influx, would require light limitation or stratification associated with sea-ice.