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Major and trace element geochemistry of lower Pliocene marine sediment core samples collected at International Ocean Discovery Program Site U1532 in the Amundsen Sea via ICP-MS. Bulk samples of mud or sandy mud were analyzed to assess sediment provenance using elemental ratios. The geochemical data were collected and analyzed by Ronald Leon and Sandra Passchier, assisted by Jessica Scheinbaum in sample preparations, and Xiaona Li in the ICP-MS analytical work. 

Abstract Mass loss from polar ice sheets is poorly constrained in estimates of future global sea-level rise. Today, the marine-based West Antarctic Ice Sheet is losing mass at an accelerating rate, most notably in the Thwaites and Pine Island glacier drainage basins. Early Pliocene surface temperatures were about 4 °C warmer than preindustrial and maximum sea level stood ~20 m above present. Using data from a sediment archive on the Amundsen Sea continental rise, we investigate the impact of prolonged Pliocene ocean warmth on the ice-sheet−ocean system. We show that, in contrast to today, during peak ocean warming ~4.6 − 4.5 Ma, terrigenous muds accumulated rapidly under a weak bottom current regime after spill-over of dense shelf water with high suspended load down to the rise. From sediment provenance data we infer major retreat of the Thwaites Glacier system at ~4.4 Ma several hundreds of km inland from its present grounding line position, highlighting the potential for major Earth System changes under prolonged future warming.