4 High latitude paleoceanographic discoveries from Scientific Ocean Drilling (IODP, ODP, DSDP)

Scientific Ocean Drilling has retrieved thousands of meters of sediment cores from the high latitude oceans.  This session provides the opportunity to present the results of work to understand Cenozoic climate and oceanographic changes.

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Room 27

Early Pliocene Current Strength Variability off West Antarctica Based on A Particle Size Record from The Resolution Drift, Amundsen Sea.

Paper number: 4-8
Program: Technical Sessions
Time: 10:20 AM – 10:40 AM

Authors

Abstract

The stability of the West Antarctic Ice Sheet under warmer-than-present conditions is a critical uncertainty in projecting future sea-level rise and requires an understanding of how ocean currents interact with the ice sheet. To address this, we investigate bottom current variability during a past warm period, the Early Pliocene, using particle size analysis of sediment cores (U1532C and U1532G) recovered from Resolution Drift in the Amundsen Sea. Grain size measurements were conducted using a Malvern Mastersizer 3000 laser diffraction analyzer, which enabled high-resolution quantification of the sortable silt fraction (10–63 µm) and calculation of mean sortable silt size (Mean SS), both of which serve as proxies for bottom current strength. Our grain-size result indicates fine-grained silts and clays with minor sand content, indicating deposition under generally low-energy conditions interspersed with episodic high-energy events. Our results show two distinct current regimes controlling sedimentation at our site: (1) persistent, weak background flow (~2–7 cm s⁻¹) driven by the westward-flowing Lower Circumpolar Deep Water, and (2) episodic high-energy accelerations reaching speeds of up to ~17 cm s⁻¹. We interpret this as a hybrid contourite-turbidite system in which meltwater-driven hyperpycnal flows, triggered by ice-sheet instability, are reworked by the Antarctic Slope Current. The interval around ~4.6 Ma shows the highest current intensification period, which we link to ice retreat phase characterized by enhanced basal melting. Our findings suggest that ocean circulation along the West Antarctic margin was dynamic during the Early Pliocene, with significant variability in bottom-current strength due to ice-sheet-ocean interactions.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411317

© Copyright 2026 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.