Diamond Hill, Darwin Glacier. A proxy for the West Antarctic ice sheet?
University of Canterbury
In the Ross Sea embayment during the Last Glacial Maximum (LGM, 18-22ka), the grounding line of the West Antarctic Ice Sheet (WAIS) advanced northwards into the Ross Ice Shelf (RIS). This effectively dammed the drainage of the Transantarctic Mountain outlet glaciers and caused significant downstream thickening of their glacier profiles (Conway et al 1999). The Darwin / Hatherton Glacial System (79.5° S, 158° E) provides a number of sites that contain geological evidence of WAIS fluctuations. Previous geomorphic and pedological studies in the area (Bockheim et al. 1989, Denton & Hughes 2000) have used these sites to constrain the timing and magnitude of the LGM ice sheet advances. As Diamond Hill lies at the confluence of the Darwin Glacier and RIS its glacial geomorphology should reflect the thickening caused by the advancing WAIS. Insitu cosmogenic nuclide dating has being used at sites along the Darwin/Hatherton as a proxy to recreate the timing and magnitude of both WAIS and EAIS advances. By measuring the concentrations of Beryllium-10 and Aluminium-26 in quartz rich lithologies, the time since the deposition of a moraine can be calculated. Early interpretations based on cosmogenic ages from the Lake Wellman area (Fink et al 2009, Storey, et al. 2010) show up to 800 meters of thickened ice approximately 2 million years ago. Moraines previously assumed to be the limit of LGM ice expansion, date to 30-40 ka. This suggests that while early EAIS Quaternary expansion was large; ice volume at the LGM may be little changed from the present. Two transects were sampled on Diamond Hill that cover an altitude range of 1100 meters. Preliminary 10Be cosmogenic dates show a similar trend to that seen further up glacier in Lake Wellman, in the case of Diamond Hill the WAIS was approximately 900 meters thicker than the current Rose Ice Shelf configuration at ~1.5Ma and with only small advances in the last 10ka. As with Lake Wellman no evidence of large scale LGM advances were found.
Antarctica, Ice, Glaciers, Expansion, Beryllium 10, Age estimation
Joy, K., Storey, B., Fink, D., & Shulmeister, J. (2010). Diamond Hill, Darwin Glacier. A proxy for the West Antarctic ice sheet? Poster presented to the Annual Antarctic Conference 2010 - "A Taste of the Ice", 5th – 7th July 2010. In Proceedings of the Annual Antarctic Conference 2010, (pp. 57). Christchurch, New Zealand: University of Canterbury.