A multi-proxy investigation of northeast Irish Ice Sheet dynamics during the Last Glacial-Interglacial Transition

Recent state-of-the-art research has provided valuable insights into the driving mechanisms of the marine-based retreat of the last British-Irish Ice Sheet (BIIS) c. 26-20 ka BP during the Last Glacial period. However, the timing, nature, and drivers of BIIS retreat as it transitioned to a terrestrial-based ice mass c. 20-15 ka BP are poorly understood. During this time, the BIIS was rapidly losing mass under oscillatory climate conditions and high sea levels around Europe. Deeper investigations of this behaviour will therefore improve our understanding of how analogous present-day ice sheets will undergo the same transition in the future.

This project aimed to unravel the drivers and influences of deglaciation during the marine- to terrestrial-based transition of the northeast Irish Ice Sheet (a central sector of the BIIS) c. 20-15 ka BP. This region in the northeast of Ireland is key for investigating the intrinsic and extrinsic drivers of BIIS retreat in the backdrop of oscillatory climate conditions during the Last Glacial-Interglacial Transition. High-resolution geomorphological mapping and sedimentological strategies were combined with a novel multi-geochronological approach for the first time in the region to achieve the overall project aim.

Dynamics of the northeast Irish Ice Sheet were complex as it transitioned to a terrestrial-based ice mass, revealing this sector of the BIIS was dynamically unstable during a period of thinning and reorganisation. Tephrochronology and varve chronology at a key palaeolake basin produce a novel and accurate minimum age for deglaciation, and a new Bayesian age model of ice sheet retreat allows the drivers of deglaciation to be investigated in detail. Intrinsic drivers are primarily responsible for rapid retreat, even during cold stadial conditions c. 20-16 ka BP. A period of climate warming c. 15.0-15.5 ka BP drove the catastrophic demise of the central BIIS as it thinned over soft sediment.