Abstract
Ice streams in the Pine Island-Thwaites region of West Antarctica currently dominate contributions to sea level rise from the Antarctic ice sheet. Predictions of future ice-mass loss from this area rely on physical models that are validated with geological constraints on past extent, thickness and timing of ice cover. However, terrestrial records of ice sheet history from the region remain sparse, resulting in significant model uncertainties. We report glacial-geological evidence for the duration and timing of the last glaciation of Hunt Bluff, in the central Amundsen Sea Embayment. A multi-nuclide approach was used, measuring cosmogenic 10Be and in situ14C in bedrock surfaces and a perched erratic cobble. Bedrock 10Be ages (118–144 ka) reflect multiple periods of exposure and ice-cover, not continuous exposure since the last interglacial as had previously been hypothesized. In situ14C dating suggests that the last glaciation of Hunt Bluff did not start until 21.1 ± 5.8 ka – probably during the Last Glacial Maximum – and finished by 9.6 ± 0.9 ka, at the same time as ice sheet retreat from the continental shelf was complete. Thickening of ice at Hunt Bluff most likely post-dated the maximum extent of grounded ice on the outer continental shelf. Flow re-organisation provides a possible explanation for this, with the date for onset of ice-cover at Hunt Bluff providing a minimum age for the timing of convergence of the Dotson and Getz tributaries to form a single palaeo-ice stream. This is the first time that timing of onset of ice cover has been constrained in the Amundsen Sea Embayment.
Highlights
Ice mass loss from the Pine Island-Thwaites drainage basins of the Amundsen Sea sector presently dominates the Antarctic contribution to global sea level (Shepherd et al, 2012; King et al, 2012), and research has focused on this region (e.g. Joughin and Alley, 2011; Alley et al, 2015)
This study focuses on determining the deglacial history of presently exposed bedrock at Hunt Bluff, which is situated on the west side of Bear Peninsula, 140 km north-west of Thwaites Glacier and adjacent to the Dotson Ice Shelf (Fig. 1)
The 14C measurements in the erratic cobble and bedrock suggest that Hunt Bluff last became glaciated at 21.1 ± 5.8 ka, which coincides with the Last Glacial Maximum (LGM) (Fig. 3B)
Summary
Ice mass loss from the Pine Island-Thwaites drainage basins of the Amundsen Sea sector presently dominates the Antarctic contribution to global sea level (Shepherd et al, 2012; King et al, 2012), and research has focused on this region (e.g. Joughin and Alley, 2011; Alley et al, 2015). In order to better constrain ice sheet history of the region and improve reconstruction of its past ice dynamics in physical models, here we provide glacial-geological evidence of the timing e both onset and final deglaciation e of the last glacial cover in the central ASE from a site adjacent to the Dotson Ice Shelf (Fig. 1). Their review showed that, whilst the deglacial history of the Dotson-Getz palaeo-ice stream, which formerly drained the coast of Marie Byrd Land outboard of Smith Glacier, is relatively well-understood (Smith et al, 2011), there are only very sparse terrestrial geological data (Johnson et al, 2008; Lindow et al, 2014) constraining ice sheet thickness in the area since the Last Glacial Maximum (LGM)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
