Slide 1

Amanda Mosola and Dr. John Anderson Funding: NSF Office of Polar Programs WAIS 2003 Evidence for Evacuation of the West Antarctic Ice Sheet before the LGM in the eastern Ross Sea Slide 2 Research Objectives Position of the grounding line at glacial maximum History of advance and retreat Substrate control on ice stream behavior Timing of retreat Slide 3 Petrologic Provinces/ice sheet flow West Antarctic Ice Sheet East Antarctic Ice Sheet Anderson et al, 1984 Slide 4 Dataset Slide 5 Grounding Zone Wedges 100 m 5 km 50 m Slide 6 Slide 7 Ice Stream Margin Slide 8 Slide 9 Eastern Ross Sea Synthesis of Ice Sheet Advance and Retreat Slide 10 till glacial-marinecontact Slide 11 Chronologic Constraint - Radiocarbon Dating Scarcity of foraminifera Acid insoluble organic matter Discrepancy in surface ages Foraminifera Ocean reservoir correction 1200 1300 yrs Acid insoluble organic matter 1000 + years older Ages increase west to east Gordon et al, 1992, Berkman and Formann, 1996 Andrews et al, 1999 Slide 12 Slide 13 Impact of Carbon Recycling t = ( ln2)ln(A o /((ks/100)A s + (kc/100)A c )) A = 100/e t/8033 T= age of sample,A = 14 C activity, yrs, k = % contamination Slide 14 Slide 15 Conclusions Maximum grounding line at shelf edge Rapidly streaming ice deforming the bed Migration of boundaries Sharp Ice Stream margins Mass Wasting of the Ice Sheet No ice shelf formation Rapid episodic ice sheet advance and retreat Ice sheet retreat before the LGM