Dynamics of the British-Irish Ice Sheet in the South of Ireland.

Accurate reconstructions of past ice sheet dynamics are essential for constraining ice sheet sensitivity to climate forcing and projecting future sea-level rise in a warming climate. The British-Irish Ice Sheet (BIIS) during the Last Glacial Maximum presents a critical test case, and yet, reconstructions of its southern margin across Ireland differ fundamentally in both extent and timing.
 
Earlier geomorphic mapping-based models proposed an ice-free corridor across southern Ireland during the last glacial period. In contrast, more recent offshore and near-shore sediment-based reconstructions propose a maximum BIIS extent covering the entire island and extending to the continental shelf edge, requiring an ice sheet thick enough to override most Irish mountain ranges. This interpretation conflicts with evidence for localized mountain glaciation in the same time period in areas like the Wicklows Mountains, which would have been impossible under a thick ice sheet. The scarcity of reliable terrestrial geochronological control points (e.g., cosmogenic exposure ages, OSL, ¹⁴C) in southern Ireland significantly contributes to these uncertainties, thus limiting the accuracy of reconstructions of BIIS expansion and retreat.
 
This project aims to resolve these contradictions by providing robust chronological control on the position of the BIIS margin in the south of Ireland. We conducted sampling campaigns in three critical locations: the Wicklow Mountains, the Comeragh Mountains, and the Kerry Peninsula. Our sampling strategy targeted boulders at multiple elevations and aspects to capture both the timing and geometry of ice cover. We present preliminary ¹⁰Be surface-exposure ages from erratic boulders in the Comeragh Mountains (maximum elevation 792 m), sampled on transects from the northern, eastern, southern, and western slopes.
 
These chronological constraints will refine deglaciation scenarios for the BIIS southern margin, in turn improving our understanding of regional landscape evolution, and provide empirical data for testing ice sheet models under past climate conditions similar to future warming scenarios.