Antarctica at the global ‘Last Glacial Maximum’ – what can we learn from cosmogenic 10Be and 26Al exposure ages?.

• Main Author: Fink, D
• Format: Conference Object
• Language: English
• Published: AMS-13 2017
• Subjects: Ice; Antarctica; Glaciers; Bedrock project; Seas; Cosmology; Antarctic; East Antarctica; Framnes; Glacier Shackleton; Hatherton Glacier; Ross Ice Shelf; Shackleton; Shackleton Range; Southern Ocean; Vestfold; Vestfold Hills; West Antarctica; Antarc*; Ice Sheet; Ice Shelf
• Online Access: http://apo.ansto.gov.au/dspace/handle/10238/8286; http://ams13.cerege.fr/Vote%20for%20AMS13%20in%20Aix%20en%20Provence%20!!_fichiers/AMS13_All_Abstracts.pdf

Ice volume changes at the coastal margins of Antarctica during the global LGM are uncertain. The little evidence available suggests that behaviour of the East and West Antarctic Ice Sheets are markedly different - and complex. It is hypothesised that during interglacials, thinning of the Ross Ice Shelf, a more open-water environment and increased precipitation, allowed outlet glaciers draining the Transantarctic Mnts and fed by interior Ice Sheets to advance during moist warmer periods, out of phase with colder arid periods. In contrast, glacier dynamics along the vast coastal perimeter of East Antarctica is strongly influenced by Southern Ocean conditions. Cosmogenic 10Be and 26Al chronologies, although restricted to ice-free ”oasis” and mountains flanking drainage glaciers, has become an invaluable, if not unique, tool to quantify Pleistocene ice sheet variability. Despite major advances, extracting reliable ages from glacial deposits in polar regions is problematic - recycling of previously exposed/ buried debris and continual post-depositional modification leads to age ambiguities for a coeval glacial landform. More importantly, cold-based ice advance can leave a landform unmodified resulting in young erratics deposited on ”ancient” bedrock. Exposure ages from different localities throughout East Antarctica (Framnes Mnts, Lutzow-Holm Bay, Vestfold Hills) and West Antarctica (Denton Ranges, Hatherton Glacier, Shackleton Range) highlight some of the new findings. This talk presents results which quantify the magnitude and timing of paleo-ice sheet thickness changes, questions the validity of an ”Antarctic LGM” and discusses the complexities presented by the geological spread observed in such studies.