| Summary: | Inaccessibility due to harsh weather conditions and perennial sea ice has left the Weddell Sea embayment (WSE) vastly under-studied in comparison to other regions of Antarctica. Yet understanding its deglacial history since the Last Glacial Maximum (LGM) is vital for understanding the dynamics and stability of the Antarctic ice sheet. Additionally, the debate continues as to the magnitude and timing of West Antarctic Ice Sheet (WAIS), Antarctic Peninsula Ice Sheet (APIS) and East Antarctic Ice Sheet (EAIS) advance during the LGM. Here we present geologic and geophysical evidence from the southern and eastern continental shelves of the WSE that show diachronous retreat by the WAIS and EMS. Detailed analysis of sediment cores display a retreat stratigraphy in the WSE with distal glacimarine sediments overlying proximal glacimarine deposits and till. These results, in combination with AMS radiocarbon ages, demonstrate that the grounding line of the EAIS was very near that of present day as early as 30,476 cal yr BP and indicate little, if any, advance of the EMS during the LGM. In contrast, multibeam swath bathymetry data show mega-scale glacial lineations, indicative of grounded, flowing ice in two troughs on the southern continental shelf, which drain ice from the WAIS. Although there are no radiocarbon ages to absolutely constrain the timing of this grounding event on the southern continental shelf, we interpret the lineations as LGM age based on their pristine nature. Further, there are similar geomorphic features on the western continental margin where the LGM timing of APIS advance has been demonstrated. Thus, during the LGM, the Antarctic ice sheets behaved independently in the WSE.
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