Meeresbodenmorphologie und glaziale Geschichte im Umfeld des Ekströmisen

• Main Author: Eisen, Olaf
• Format: Conference Object
• Language: unknown
• Published: 2022
• Subjects: Ekström Ice Shelf; Ekströmisen; Ice Sheet; Ice Shelf
• Online Access: https://epic.awi.de/id/eprint/56285/; https://hdl.handle.net/10013/epic.c654e230-11a8-40cd-b796-c69394487db3

Based on the results published in Ötting et al., 2022 (https://doi.org/10.5194/tc-16-2051-2022) we present a compilation of geophysical surveys in front of and beneath the Ekström Ice Shelf, to identify and interpret evidence of past ice-sheet flow, extent and retreat. The sea floor beneath the Ekström Ice Shelf is dominated by an incised trough, which extends from the modern-day grounding line onto the continental shelf. Our surveys show that mega-scale glacial lineations cover most of the mouth of this trough, terminating 11 km away from the continental shelf break, indicating the most recent minimal extent of grounded ice in this region. Beneath the front ∼30 km of the ice shelf measured from the ice shelf edge towards the inland direction, the sea floor is characterised by an acoustically transparent sedimentary unit, up to 45 m thick. This is likely composed of subglacial till, further corroborating the presence of past grounded ice cover. Further inland, the sea floor becomes rougher, interpreted as a transition from subglacial tills to a crystalline bedrock, corresponding to the outcrop of the volcanic Explora Wedge at the sea floor. Ice retreat in this region appears to have happened rapidly in the centre of the incised trough, evidenced by a lack of overprinting of the lineations at the trough mouth. At the margins of the trough uniformly spaced recessional moraines suggest ice retreated more gradually. We estimate the palaeo-ice thickness at the calving front around the Last Glacial Maximum to have been at least 305 to 320 m, based on the depth of iceberg ploughmarks within the trough and sea level reconstructions.