Eccentricity modulation of East Antarctic Ice Sheet in Wilkes Land over the past 6 million years

During past warm intervals of the Pliocene to Pleistocene, global sea levels are proposed to have been up to 20-30 m higher than present, inferring loss of Greenland, the West Antarctic Ice Sheet, as well as large areas of the marine-based sectors of the East Antarctic Ice Sheet. Here, we present a new compilation of geological proxies for shifting ice sheet dynamics from the offshore of the Wilkes subglacial drainage basin of East Antarctic (3-4 m sle), with a continuous orbital-scale record of ice rafted debris and geochemical provenance proxies over the past 6 million years. Eccentricity (100 kyr) pacing is pervasive in ice rafted debris throughout most of this time period. Obliquity frequencies (40 kyr) are a subordinate signature, despite obliquity usually being implicated in marine-based AIS collapse, but do show strong power for short intervals of ~500 kyr duration. These peaks in obliquity-paced ice discharge show no clear relationship to the strength of obliquity forcing, but instead show a near linear relationship to phases of enhanced eccentricity. Our results, and comparisons to ice sheet modelling experiments, suggests that marine-based ice sheet retreat into the interior of Wilkes subglacial basin required significant atmospheric warming, regulated by the eccentricity driven shifts in seasonality and summer insolation. This acted to lower surface elevations of the EAIS, thereby removing an "ice-plug" that buffers against oceanic induced collapse of this marine-based sector of the EAIS. Our results indicate that there is an atmospheric warming threshold required to trigger major retreat of the Wilkes Land subglacial basin.