Greenland Ice Sheet dynamics and weathering regimes during past warm intervals: Evidence from micro-CT analysis of ice-rafted debris

Understanding the sensitivity of the Greenland Ice Sheet (GrIS)—a major reservoir of the terrestrial cryosphere—to past warm climates is critical for predicting its response to the ongoing global warming and for improving Earth System Models (ESMs), given GrIS strong influence on global ocean circulation and atmospheric patterns. In this study, we investigate GrIS variability across marine interglacial transitions using sedimentary micro-computed tomography (microCT) analyses of ice-rafted debris (IRD) from marine sediment core U1604B recovered in Baffin Bay during IODP Expedition 400 (Knutz et al., 2025). Baffin Bay represents a key high-latitude oceanographic gateway linking Arctic and North Atlantic circulation and integrating sedimentary signals from both the Greenland and North American ice sheets. Interglacial intervals corresponding to Marine Isotope Stage (MIS) 5 (Eemian) and MIS 11 (Holstein)—warm periods often considered analogues for ongoing global warming—were identified in core U1604B using Xray fluorescence (XRF) geochemical proxies. Approximately 40–50 sediment samples spanning these intervals were selected for high-resolution micro-CT scanning ( 1.5 μm resolution) to generate quantitative three-dimensional datasets of IRD particles. This novel approach enables non-destructive quantification of grain size, sorting, morphology, and surface microtextures. The methodological workflow integrates micro-CT imaging with mineralogical characterization and microtextural analysis of sand- and silt-sized grains (38-250 μm sieved sediments) to distinguish between glacial, glaciofluvial, fluvial, and aeolian sediment transport regimes. By combining geochemical proxy records with micro-sedimentary observations, this study aims to reconstruct variations in weathering regimes, sediment provenance, and source-to-sink transport processes associated with GrIS fluctuations during warm climate intervals. Changes in IRD fluxes and transport pathways may also reflect variations in terrigenous nutrient delivery to high-latitude marine systems, which can influence ocean productivity and climate feedback mechanisms. Furthermore, the development of this integrated micro-CT based methodology provides a new framework for linking sedimentological processes with cryosphere dynamics and biogeochemical cycling during past interglacial periods.