¹Lindsay O. Prothro, ²Wojciech Majewski, ³Yusuke Yokoyama, ⁴Lauren M. Simkins, ¹John B. Anderson, ⁵Masako Yamane, ⁶Naohiko Ohkouchi

¹Department of Earth, Environmental and Planetary Science, Rice University; ²Department of Environmental Paleobiology, Polish Academy of Sciences; ³Atmosphere and Ocean Research Institute, University of Tokyo; ⁴Department of Environmental Sciences, University of Virginia; ⁵Institute for Space-Earth Environmental Research, Nagoya University; ⁶Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology

Paleoclimate records of ice sheet dynamics serve as important boundary conditions for models intended to predict future change. However, the development of accurate records of the most recent glacial cycle in Antarctica has been challenging due to difficulties in obtaining meaningful radiocarbon dates. Despite being the most heavily investigated region of the Antarctic continental shelf (through seismic and multibeam surveys, coring, and attempted radiocarbon dating), the record of marine-based ice sheet dynamics in the Ross Sea has remained largely elusive and at odds with terrestrial records of ice sheet thinning. Past issues stem primarily from poorly-preserved carbonate (due to elevated CCD), contamination by glacially-recycled carbon, and limited consideration for geomorphic context and detailed sedimentary facies analysis when interpreting radiocarbon dates. The western Ross Sea, formerly covered by the East Antarctic Ice Sheet (EAIS) during the Last Glacial Maximum, shows evidence of a highly complex retreat pattern, but the timing remains uncertain. We reassess over 300 previously published and over 70 newly acquired radiocarbon ages within the context of a consistent sedimentary facies framework, with attention to geomorphic indicators of grounding-line position, to interpret the extent and timing of the local glacial maximum and subsequent retreat of the EAIS. We find that the ice streams flowing through Pennell and JOIDES troughs held their maximum extent for approximately 10,000 years before retreating at 14 and 11 cal ka BP, respectively. Due to new marine constraints, we can now link the drawdown of terrestrial ice near Ross Island at approximately 7.8 cal ka BP to a major ice shelf collapse and subsequent small readvance of Transantarctic outlet glaciers through southern JOIDES Trough.