Holocene Marine-Based Ice Sheet Instability in the Ross Sea

• Main Authors: McKay, Robert, Golledge, Nicholas R., Maas, Sanne, Naish, Tim, Levy, Richard H., Dunbar, Gavin, Kuhn, Gerhard
• Format: Conference Object
• Language: unknown
• Published: 2015
• Subjects: Antarc*; Antarctic; Antarctica; Byrd Glacier; Ice Sheet; Ice Shelf; Ross Ice Shelf; Ross Island; Ross Sea
• Online Access: https://epic.awi.de/id/eprint/39059/; http://isaes2015goa.in/docs/XII%20ISAES%202015%20Abstract%20Volume.pdf; https://hdl.handle.net/10013/epic.46344

Given the hypothesized instability of marine-based ice sheets to future warming, constraining the rate of retreat under past natural warming regimes can provide new insight into the mechanics of ice sheet retreat and their sensitivity to environmental change. However, the timing of this retreat in Antarctica is variably well-constrained. In part this is due to a paucity of suitable post-LGM records, but also due to the well-documented difficulties in reliably dating marine deposits with the 14C method around Antarctica due to a lack of suitable carbonate material. Most chronologies from the marine realm in the Ross Sea are largely dependent on Acid Insoluble Organic radiocarbon ages from bulk sediments that inherently overestimate the timing of glacial retreat ages due to pervasive reworking of older carbon on the continental shelves of the Antarctic. Here, we report a lithofacies-based retreat history from the ANDRILL Coulman High drill site in the Central Ross Embayment. This site was located within the paleo-drainage path of the Byrd Glacier, the largest East Antarctic Ice Sheet outlet glacier draining in to the Ross Sea at the LGM. Planktic and benthic formaniferal-based radiocarbon dates from a laminated-diatom- and icerafted debris-bearing glaciomarine mud constrain the retreat history of the Last Glacial Maximum (LGM) ice sheet in the Ross Embayment. During post-LGM retreat of the ice sheet margin in western Ross Sea, the calving line became ‗pinned‘ in the Ross Island region and the grounding line continued its retreat toward its present day location. This establishes that the modern-day calving line location of the Ross Ice Shelf was established by the Early Holocene, and that the ice sheet retreat was initiated in the Ross Sea prior to this time, but also continued through into the mid-Holocene. We examine our results in the context of oceanic drivers and marine instability mechanisms for the LGM retreat of the ice sheets in the Ross Embayment.