Degree
Doctor of Philosophy (PhD)
Department
Geology and Geophysics
Document Type
Dissertation
Abstract
Here we combine the available chronology of post-LGM marine ice sheet retreat from Ross Sea with new mapping of seismically resolvable grounding zone wedges (GZWs). Our analysis shows that the longest stillstands occurred early in the deglacial and had millennial durations. The available chronological data shows that cessation of WAIS and East Antarctic Ice Sheet (EAIS) stillstands were highly asynchronous across at least five thousand years. Asynchronous collapse of individual catchments during the deglacial suggests that the Ross Sea sector would have contributed to multiple episodes of relatively small amplitude sea-level rise as the WAIS and EAIS retreated from the region. The high sinuosity of the modern grounding zone in the Ross Sea suggests that this style of retreat persists.
During the LGM, six ice streams experienced long-duration stillstands with grounding lines perched on the Ross Sea outer continental shelf. We used selected cores to explore whether the Ross Sea ice streams retreated with an intact ice shelf or a calving cliff. Our analysis suggests that only two ice streams retreated with a calving cliff. The other four ice streams retreated with an intact ice shelf. These results show that ice-stream collapse is not uniquely preceded by the loss of fringing ice shelves.
The recent expeditions NBP2301, NBP2302 and NBP2403 to the central Ross Sea of Antarctica sought to investigate whether Ross Bank was a paleo-pinning point of the Ross Ice Shelf during the post-LGM. Multibeam bathymetry data was combined with legacy data to map seafloor features across the bank as well as provide geomorphological context for sediment coring. CHIRP sub-bottom profiles were also acquired to support the analysis. Our analysis shows that an ice rise existed on Ross Bank prior to the southward retreat of the Ross Ice Shelf calving front. New mapping revealed a series of semi-concentric terraces rimming the bank flanks and crest that demonstrate a progressive shrinking footprint of the ice-rise area. This new geomorphological evidence of a paleo-pinning point of the Antarctic Ice Sheet provides an important paleo-perspective as to how the many modern ice sheet pinning points may destabilize.
Date
3-26-2025
Recommended Citation
Danielson, Matthew, "Regional Seismic, Core Stratigraphy and Geomorphological Analysis of Ice Sheet Retreat in Ross Sea, Antarctica Since the Last Glacial Maximum" (2025). LSU Doctoral Dissertations. 6707.
https://repository.lsu.edu/gradschool_dissertations/6707
Committee Chair
Bart, Philip J.