Dr. Margaret Jackson

Summary

Ireland's landscape is one shaped by glaciation. While a longstanding focus of inquiry and debate, the history and evolution of Ireland's glaciers have long remained uncertain, with little chronologic control on past glacial extents beyond sparse limiting radiocarbon ages [e.g., 1]. As a result, the models used to assess past ice sheet and glacier sensitivity to changing climate conditions have not been fully 'ground truthed'. This leads to greater uncertainty regarding the response of Ireland's ice to changing climate, with implications for our understanding of local (and global) ice-sheet sensitivity to climate change, regional sea-level modeling, landscape evolution, and human settlement. Recent advances in geochemistry, particularly in cosmogenic surface-exposure dating (SED), have opened the Irish landscape to direct chronologic investigation. Through applying SED to glacial landforms, we can now determine directly the past timing and magnitude of glacial fluctuations, thus providing discrete targets (spatial and temporal) for glaciological models to match. Applications of SED in Ireland have yielded novel information on the timing of former Irish Ice Sheet (IIS) recession to the Atlantic coast [2], and have placed bounds on existing IIS models during the Last Glacial Maximum (LGM) [3]. However, these data remain relatively sparse, and questions remain regarding the former elevation, extent, and dynamics of the IIS following the LGM, particularly in regions inland from the coast which were presumably unaffected by local sea level changes during deglaciation. This project will target the exceptionally well-preserved glacial landscape of Slieve Carr, Co. Mayo in northwestern Ireland (Fig. 1) to assess the timing of terrestrial IIS recession in Ireland's interior northwest. Slieve Carr hosts numerous glacial moraines that can be targeted for cosmogenic beryllium-10 SED. First-hand site inspection confirms suitable lithology, and my preliminary snowline reconstructions suggest that the most extensive former ice positions preserved at Slieve Carr pre-date the late-glacial period (15-11 ka), and may date to the earliest onset of IIS recession from the region (Fig. 2). Moreover, the site is host to moraine-dammed wetlands that provide opportunity to investigate continuous sedimentary records of environmental change (Fig. 2). Should basal sediments be well preserved, they would provide indication of the timing of IIS recession from the site, and offer opportunity to produce a local beryllium-10 production rate. This would be the first such production rate from Ireland, and may constitute one of the few production rate calibrations in the world which pre-dates the late-glacial period. Based on the results of SED and sedimentary analyses, I will then use glaciological modeling to determine the climate conditions associated with dated glacial fluctuations.

Funding Agency

British Society for Geomorphology

Programme

Early Career Research Grant