IGA Lecture: Dr Catherine Delaney (Manchester Metropolitan University) on “Revealing the FineScale Dynamics of the Retreating Irish Ice Sheet”

ABSTRACT

Melt from glaciers and ice sheets will play an increasingly important role in sea-level rise in the coming centuries.  However, the response of ice sheets and glaciers to increasing temperatures is not straightforward and varies depending on conditions at the bed of the ice sheet or glacier. As the beds of modern ice sheets are inaccessible, a paleoglaciological approach is used – using the footprint of former ice sheets to infer conditions during deglaciation.  

This talk will examine the impact of data resolution on understanding of the retreat of the last Irish Ice Sheet.  The accuracy and usefulness of paleoglacial reconstructions depends on the recognition of associated suites of landforms and deposits – glacial landsystems – and dating of these deposits.  In Ireland, eskers and low-amplitude landforms forming apparently chaotic hummocky topography are widely observed across the central Irish Midlands, and have been traditionally interpreted as evidence of ice stagnation during recession of the last Irish Ice sheet after c.20,000bp.  However, high resolution airborne Lidar and photogrammetric DTMs, aerial photo mapping and field survey, indicate that the ice sheet switched between episodes of fast ice flow associated with a warm, wet ice sheet base, and a slower, partly stagnant ice margin, with parts of the margin frozen to the underlying bed.  As the ice margin receded northwestward and westward across the Irish Midlands, large lakes were ponded between the ice margin and bedrock.  These lakes were sediment sinks, and the deposits provide a continuous record of changing sediment inputs and associated ice dynamics.  A combination of microscale sedimentological logging and micromorphological analysis indicates that these finely laminated sediments record annual variation in sediment input, and can be used to reconstruct meltwater inputs and associated ice sheet dynamics year by year.

BIOGRAPHY

Degree in Nat. Sci. TCD; PhD in Deglaciation of the Irish Midlands (eskers in particular), TCD; 5 years as a research assistant in UCC, working on the record of storms in Holocene coastal stratigraphies in the West of Ireland, Brittany and North- west Spain (lots of coring); 25 years+ atvManchester Metropolitan University. A sedimentologist and geomorphologist, specialising in landforms and deposits formed during ice retreat; have worked primarily in Ireland, but also in the UK and Iceland. Likes mud. A lot.

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