Characterizing West Antarctic Ice Sheet Dynamics during Marine Isotope Stage 5 using Analysis of Iceberg Rafted Debris

Past periods of climate warming provide valuable analogues for understanding how the West Antarctic Ice Sheet (WAIS) may respond to ongoing climate change and its potential contribution to sea-level rise. Because the WAIS is highly vulnerable to ocean-driven melting, identifying the conditions that led to past ice-sheet retreat is critical for improving projections of future changes. This study investigates the relationship between ocean warming, iceberg melting, and environmental change by comparing marine sediment records from IODP Site U1533, in the Amundsen Sea near Thwaites Glacier, and ODP Site 1101, west of the Antarctic Peninsula. Iceberg-rafted debris (IRD) was used as a proxy for iceberg discharge and ice-sheet instability, Ba/Rb ratios were used to reconstruct changes in marine productivity associated with warmer interglacial conditions, and magnetic susceptibility measurements were analyzed to identify variations in sediment composition associated with changes in depositional processes. Focusing on Marine Isotope Stage 5 (MIS 5) and comparing multiple interglacial intervals, we evaluate how these proxy records respond to ocean warming. Pronounced IRD peaks occur at the onset and termination of interglacial periods, indicating increased iceberg melting. Ba/Rb ratios also increase during interglacial intervals, consistent with enhanced marine productivity under warmer ocean conditions. These results suggest that the WAIS responds rapidly to relatively modest ocean warming and that periods of climate transition represent an increase in ice-sheet instability. This work improves our understanding of WAIS sensitivity to ocean warming and provides insights for predicting future Antarctic contributions to global sea-level rise.过往的气候变暖事件，为理解西南极冰盖（West Antarctic Ice Sheet, WAIS）如何响应当前持续的气候变化及其对海平面上升的潜在贡献，提供了极具价值的类比参照。由于西南极冰盖极易受到海洋驱动的融化影响，明确过往冰盖退缩的触发条件，对优化未来气候变化预测至关重要。本研究通过对比位于思韦茨冰川附近阿蒙森海的国际大洋发现计划（International Ocean Discovery Program, IODP）U1533站位与南极半岛西侧的大洋钻探计划（Ocean Drilling Program, ODP）1101站位的海洋沉积物记录，探究海洋变暖、冰山融化与环境变化之间的关联。研究以冰山筏运碎屑（Iceberg-rafted debris, IRD）作为冰山排放与冰盖不稳定性的代用指标，以钡/铷（Ba/Rb）比值重建与温暖间冰期环境相关的海洋生产力变化，并通过磁化率测量分析沉积作用过程变化所对应的沉积物组分差异。本研究聚焦海洋同位素第5阶段（Marine Isotope Stage 5, MIS 5），并对比多个间冰期时段，评估上述代用指标记录对海洋变暖的响应模式。间冰期的起始与终止阶段均出现显著的IRD峰值，表明彼时冰山融化活动加剧。间冰期时段内的Ba/Rb比值同样升高，这与温暖海洋环境下海洋生产力提升的结果相一致。上述结果表明，西南极冰盖会对相对温和的海洋变暖做出快速响应，而气候转型时段则对应冰盖不稳定性的增强。本研究加深了我们对西南极冰盖海洋变暖敏感性的认知，并为预测未来南极冰盖对全球海平面上升的贡献提供了新的见解。