HOLOCENE GLACIAL DYNAMICS OF EAST ANTARCTICA DETECTED BY BERYLLIUM ISOTOPE RATIOS FROM THE ADÉLIE BASIN
The stable isotope 9Be is released through chemical weathering of bedrock and leaves the weathering zone with meltwater discharge. Therefore, in Antarctica high values of 9Be reflect periods of increased basal erosion. Here, we re-examine the Adélie Basin marine sediment core using 10Be/9Be ratios to assess periods of East Antarctic meltwater fluctuations during the Holocene. The 10Be/9Be isotope data indicate increased meltwater discharge after grounded ice retreated from the Adélie Basin from 9.9 to 9.2 ka BP. Sediment from basal erosion and freshwater from the local retreating ice sheet in Wilkes Basin supplied the Adélie Basin with 9Be and meteoric 10Be. This is reflected in the lithology of the core and the Al2O3/TiO3 ratio, which has the highest values at the bottom of the core indicating enhanced weathering. The increase in 10Be/9Be from 4 to 3.3 ka BP and again from 2 ka BP occurs concurrently with continent-wide ice retreat due to late Holocene strengthening of the Southern Westerly Winds and associated Circumpolar Deep Water upwelling onto the continental shelf resulting in increased Southern Ocean stratification and enhanced sea ice cover. Warm subsurface waters due to the insulating effect of sea ice cover may have enhanced the melting effect during this period.