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This dataset contains measurements of particle-size distributions on sediment from International Ocean Discovery Program Site U1533. Carbonate, and organic matter were removed through addition of 10mL aliquots of 30% H2O2 and 2mL aliquots of 10% HCl to ~50-100mL suspension on a hot plate. Dispersion was through heating with sodium pyrophosphate. Samples were measured on a Malvern Mastersizer 2000 with a Hydro 2000MU (A) accessory, using a Refractive index of 1.6 (Illite) and an absorption coefficient of 0.9. Results are in (vol. %) per size class, with diameter range equivalent to the diameter of spheres with the same volume as measured particles. 

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. 

In this study, sediments from the Pliocene warm period (3-5 million years ago) from a sediment drift deposit in the Amundsen Sea in Antarctica (drillsite U1533) were treated and analyzed for particle size distribution and sortable silt percentage. These variables help explain how fast ocean currents were moving under warmer climate scenarios. The sediments from beneath the seafloor were treated using hydrogen peroxide to break down any organic matter, followed by boiling with hydrochloric acid to break down carbonate. To remove chemicals, the sediment samples were placed into a centrifuge with 50 mL of DI water for 30 minutes, decanted, then another 30 minutes with 50 mL of DI water. After the samples were treated, they were placed into the Malvern Mastersizer 2000 to measure particle size distributions by using a laser and the resulting scatter patterns of the sediment particles. The results were graphed with depth beneath the seafloor to show the differences in sortable silt percentage over time. The results showed that the sortable silt percentage was low around the onset of the warm period, concluding that the movement of ocean currents during this time period dropped. These results were not typical, as models had predicted that warm periods would have faster ocean currents, and opens up the possibility for future research.