Past ice dynamics and unusual ramp bedforms offshore Brunt Ice Shelf, Weddell Sea

• Main Authors: Arndt, Jan Erik, Hillenbrand, C. D., Larter, R. D., Dorschel, Boris, Sørlie, S. H., Forwick, M., Smith, J. A., Wacker, Lukas
• Format: Conference Object
• Language: unknown
• Published: 2019
• Subjects: Brunt Ice Shelf; Ice Sheet; Ice Shelf; Ice Shelves; Sea ice; Weddell Sea
• Online Access: https://epic.awi.de/id/eprint/53415/; https://hdl.handle.net/10013/epic.321518f9-5eb2-4637-a1fc-0323d686926e

Past ice dynamics are so far only poorly resolved in the southern Weddell Sea. This is highlighted by previous studies that led to two contradicting scenarios for the grounding line location during the Last Glacial Maximum (LGM), which differed by up to ~650 km. Another study suggested that the maximum ice extent locally was not reached during the LGM but in the early Holocene, indicating that there was also a highly dynamic ice sheet system during deglaciation. There is ambiguity about the history of ice advance and retreat in the region offshore Brunt Ice Shelf based on current data. Only one radiocarbon dated marine geological core is available, contains age reversals, and can be interpreted as indicating ice free conditions during the LGM or having been overrun by grounded ice between 30.2-20.3 cal ka BP. Today, the Brunt Ice Shelf itself is a focus of interest due to the critical crack/fracture development since 2016. This endangers Halley research station, which is situated on the ice shelf, and has resulted in the third consecutive year of austral winter closure. Geophysical ice shelf investigations revealed that, unlike usual ice shelves, the Brunt Ice Shelf consists of numerous blocks of meteoric/glacial ice that are “glued” together by freezing sea ice and snow drift. It is hypothesized that the Brunt Ice Shelf sustains its stability due to buttressing at the McDonald Ice Rumples, which form the only remaining ice shelf pinning point. Improved understanding of the past development of the ice shelf system may also aid understanding the processes active today. We investigated hydroacoustic data that were acquired offshore Brunt Ice Shelf over the last decades with RV Polarstern and RRS James Clark Ross for geomorphological indications of past ice sheet dynamics. The identified landforms show that major ice discharge during the LGM was not via Brunt Basin just in front of the modern-day Brunt Ice Shelf, but via an ice stream that occupied Stancomb-Wills Trough, which is located northeast of Brunt Ice ...