Holocene Antarctic subglacial weathering and ice-sheet history reconstructed using the authigenic 10Be/9Be ratios of sediments from lake Maruwan Oike, Antarctica

Glaciers play an important role in the climate system via freshwater storage and the transportation of various materials from the continents to the oceans. Enhanced silicate weathering resulting from the latter can drive a reduction in atmospheric CO₂. Although these processes are known to be important through geological time, temporal changes in chemical weathering intensity are not well understood. During the last deglaciation, the East Antarctic Ice Sheet (EAIS) retreated significantly (Mackintosh et al., 2014; Yamane et al., 2011), forming isolated basins via glacio-hydro-isostatic adjustment (GIA) related crustal uplift. Sediment accumulated in these lakes provide a unique record of subglacial weathering throughout deglaciations when global temperatures and pCO₂most notably rose.

Meteoric ¹⁰Be is produced in the atmosphere by cosmic rays and delivered to the ocean surface where they adhere to suspended particles in the water column and subsequently accumulate on the basin floor (Scherer et al, 1998). Permanent ice cover prevents ¹⁰Be flux to underlying sediments and down-core variations in ¹⁰Be can therefore be utilised to reconstruct ice-sheet history (e.g., Scherer et al, 1998; Yokoyama et al., 2016). Stable ⁹Be is present in silicate rocks and is released during subglacial weathering (Sjunneskog et al., 2007), with little simultaneous release of ¹⁰Be (Scherer et al., 1998), and transported to the oceans via meltwater outflow. When Be is incorporated into the authigenic phase of marine sediments, the ¹⁰Be/⁹Be reflects that of the overlying water column (von Blanckenburg et al., 2014), which in turn reflects the relative dominance of ice-sheet exposure and/or subglacial weathering.

Here, we present authigenic ¹⁰Be/⁹Be ratios for a sedimentary core from Lake Maruwan Oike situated at the head of the Rundvåg glacier in the Lützow-Holm Bay area of East Antarctica. Sedimentary material from L. Maruwan Oike provides an 6,000 year record of subglacial weathering and nutrient input from the nearby glacier (Takano et al., 2015). Authigenic ¹⁰Be/⁹Be records reflect variations in ice-cover, subglacial weathering and marine inputs providing further constraints on EAIS fluctuations during the Holocene and offers an insight into the behaviour of beryllium in high-latitude subglacial-marine systems.