Melting of Totten Glacier, East Antarctica since the Last Glacial Maxima Revealed by Beryllium Isotope Ratios and Grain Size Analysis of Marine Sediment Records

Reducing uncertainties in sea level rise projection is of great importance for adaptation and mitigation measures. Current projections of global sea level rise by 2100 range from 0.28 m to 2 m depending on emission scenarios. Another uncertainty is in the response of Antarctic Ice Sheet to the warming climate. Such uncertainty may be reduced by better understanding the ice sheet dynamics of marine-terminating glaciers since the Last Glacial Maxima. These glaciers are especially unstable since they are susceptible to marine ice sheet instability, a positive feedback of grounding line retreat that could trigger irreversible ice discharge and hence an increase in sea level. The inherent instability of marine ice sheets affects the majority of glaciers in West Antarctica, but it also affects large regions of East Antarctica. One such key region in East Antarctica is the Aurora Subglacial Basin, which drains ice through the Totten Glacier, potentially the largest drainage system in East Antarctica most sensitive to present climate change, on the Sabrina Coast.

The physical, elemental, and isotopic composition of marine sediments give us hints of how the ice has reacted to past climate variability. We used a multi-proxy approach, analyzing 10Be, 9Be, 10Be/9Be and grain size of a sediment core (PC01) collected from the continental slope off the Totten Glacier and compared the results with other local proxies to evaluate the glacial dynamics and its relationship with Southern Ocean circumpolar currents since the Last Glacial Maximum. A slight increase of 10Be/9Be at ~17 ka BP marks the beginning of deglaciation of the Totten Glacier sector of the East Antarctic Ice Sheet. This was followed by rapid deglaciation and meltwater influx from ~9 ka BP, likely due to the intrusion of modified Circumpolar Deep Water to the grounding zone of the Totten Glacier, indicated by a simultaneous increase in 10Be, 9Be and 10Be/9Be. The intrusion of warm modified Circumpolar Deep water may be coupled with a weaker Antarctic Slope Current and a southward shift of Antarctic easterlies. We present the first 10Be/9Be records from the Sabrina Coast, which contribute to a better understanding of the dynamical response of marine-terminating glaciers to climate variability during the last deglaciation.