West Antarctic ice volume variability paced by obliquity until 400,000 years ago

Benthic foraminiferal oxygen isotopic and ice core records have been interpreted to indicate that Antarctic ice volume variations began to be paced by 100,000-year-long eccentricity cycles about 800,000 years ago. However, this interpretation has never been confirmed from sedimentological reconstructions of ice margin advance and retreat cycles around Antarctica. Here we present sedimentological and palaeomagnetic records from a 6.21-metre-long sediment core spanning the last 1.1 million years that track the proximity of the ice margin in the Ross Embayment. The advance and retreat of the Ross Ice Shelf—and by extension the West Antarctic Ice Sheet—are found to have been primarily paced by 41,000-year-long obliquity cycles until at least 400,000 years ago. We suggest that high-latitude insolationcontrolled Southern Ocean heat uptake and continued to be the main pacemaker of Antarctic glaciations well into the late Pleistocene. Insolation was predicted to control Antarctic ice volume; however, the frequency of glacial cycles inferred from distal records suggested that the 100,000-year-long cycle dominated, implying that other forcing mechanisms were at play. Our study reconciles the historical mismatch between the inferred glacial cycles and the insolation record.