Post-LGM grounding line and calving front translations of the West Antarctic Ice Sheet in the Whales Deep paleo-ice-stream trough, eastern Ross Sea, Antarctica

Newly acquired multibeam data from the Whales Deep Basin show lineations that extend to the shelf break, providing documentation that the West Antarctic Ice Sheet (WAIS) extended across the entire continental shelf during the Last Glacial Maximum (LGM). Following the LGM, the grounding line retreated approximately 60 km where it was pinned on a bathymetric high and began constructing a composite grounding zone wedge composed of seven individual wedges. Stabilization of the grounding line was thus caused by construction this composite wedge, elevating the grounding line by ~140 meters. Sedimentological data indicate that a small ice shelf with a calving front near the shelf edge formed over the outer shelf immediately after the grounding line began retreating from the shelf edge. The ice shelf broke up sometime after the fourth wedge was constructed. After construction of GZW7, the grounding line abruptly shifted ~200 km to the south where retreat slowed near the northern end of Roosevelt Island. Concomitant with grounding-line retreat, a second larger paleo Ross Ice Shelf reformed over the middle continental shelf. This large ice shelf then retreated abruptly and the present-day open water environment was established. These data indicate a complex deglaciation, which involved several discrete steps of the grounding line during the initial stages followed by a final major retreat of both the grounding line and calving front. The sedimentologic framework presented here is significant because it is a necessary step towards developing a detailed retreat chronology for this sector of the WAIS