- Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany (lingyan.luo@awi.de)
The West Antarctic Ice Sheet (WAIS) presumably collapsed multiple times during past warm periods, significantly influencing past sea levels. Recent studies have shown that different parts of the WAIS advanced and retreated asynchronously during the Mid-Pliocene Warm Period, posing a key uncertainty in ice sheet reconstruction. Along the West Antarctic continental margin, deep-sea contourite drifts receive fine-grained sediments from mixed down-slope (turbidite) and along-slope (contourite) deposition, alongside ice-rafted debris (IRD) of various densities. These sediments reflect interactions between ice sheet dynamics and ocean circulation and are therefore important indicators of the glaciation history.
This study focuses on the Bellingshausen Sea sector of WAIS, a region with high sensitivity to climate changes and a well-preserved sedimentary record. Using seismic stratigraphy and deep-sea proxies, we constrain the timing of major changes in ice volume and ocean conditions. Analysis of seismic data collected in the area of Drift 7 off the western Antarctic Peninsula identified six seismic subunits within Pliocene–Pleistocene sequences. Drill-core evidence from ODP Leg 178 suggests a warm Mid-Pliocene (4.2–3.4 Ma) with at least five ice sheet retreats, consistent with the so-called Pliocene Amundsen Sea Warm Period (4.2–3.2 Ma), but preceding the global Mid-Piacenzian Warm Period (3.3–3.0 Ma). A cooling trend began in the Late Pliocene (3.4–2.6 Ma), evidenced by reduced bio-productivity and low IRD content. Glacial conditions persisted in the Pleistocene with widespread ice rafting. Multiple intervals with abundant calcareous microfossils suggest intermittent warm periods with probably open ocean conditions.
The seismic profiles also reveal sediment transport patterns and unconformities across contourite drifts. Correlations between Drift 7 and Drift 6 reveal disparities in sedimentation rates since the late Miocene, along with the abandonment of a Miocene-Pliocene channel on Drift 6’s northeast flank. During the late Pliocene, a more erosive and far-reaching deep-sea channel formed between Drifts 6 and 7, possibly due to large amounts of downslope sediments from massive ice advance and reorganization of drainage pathways.
This work is the first step towards quantifying any asynchronicity in ice-sheet dynamics along the broader West Antarctic margin, aiding future refinements in ice-sheet modeling and climate reconstructions.
How to cite: Luo, L., Uenzelmann-Neben, G., and Gohl, K.: Sedimentary evidence of asynchronous glacial evolution along the Bellingshausen Sea sector of the West Antarctic Ice sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11220, https://doi.org/10.5194/egusphere-egu25-11220, 2025.