The last glaciers of the Wicklow Mountains

This is an interesting article which looks at the evidence for the last small glaciers in the Wicklow Mountains,  in Younger Dryas / Zone III / Loch Lomond / NS  times, around 12,000 years ago.  There are interesting comparisons with other Irish mountain areas and with Scotland, where the extent of this new glacierisation was much more dramatic.

These small glaciers -- just seven of them -- can be classified as cirque glaciers, and the authors incorporate evidence of three types of associated moraines, each one dependent upon certain glaciological conditions.   Three of the studied glaciers do not look much like cirque glaciers at all, but more like elongated snowpatches or snowfields on NE-facing steep slopes where snowdrift accumulations occurred. Were these really small glaciers (with flowing ice capable of transporting detritus) or were they small firn fields fronted by pro-talus ramparts or ridges of frost-shattered debris that simply slid down the snow surface from exposed cliff edges? I would have liked something in the article about stone and boulder shapes in the three moraine types, which might have given us a clue........

But these are small matters, and the cosmogenic dating evidence presented by the authors (based on the sampling of morainic boulder surfaces) is rather convincing.

Lauren Knight, Clare M. Boston, Harold Lovell, Timothy T. Barrows, Eric A. Colhoun, David Fink, Nicholas C. Pepin.  05 March 2025 
Restricted cirque glaciers in the Wicklow Mountains, Ireland, during the Nahanagan Stadial (Greenland Stadial-1/Younger Dryas). 

Journal of Quaternary Science  

https://doi.org/10.1002/jqs.3699

ABSTRACT

In Ireland, the Nahanagan Stadial (NS) was characterised by cirque glacier, plateau icefield and mountain ice cap expansion and is named after the cirque glacier type-site of Lough Nahanagan in the Wicklow Mountains. This period is broadly equivalent to the Younger Dryas Stadial and Greenland Stadial-1 (GS-1: ~12.9–11.7 ka). Here, we provide the first evaluation of the full extent of NS glaciation in the Wicklow Mountains by combining solar radiation modelling, mapping of glacial geomorphology, 10Be and 26Al cosmogenic surface exposure dating, 3D glacier reconstructions and analysis of snowblow and avalanching potential. We identify seven sites that hosted cirque glaciers at this time. Glacier extent was very restricted, with most glaciers only partially filling their cirques. Equilibrium line altitudes (ELAs) ranged from 470 ± 5 m a.s.l. (Lough Nahanagan) to 721 ± 5 m a.s.l. (Lough Cleevaun), with an average ELA of 599 m a.s.l. Higher snowblow and avalanching contributions at sites with lower ELAs demonstrate local topoclimatic influence on glacier growth and preservation alongside regional climate. The Wicklow Mountains provides a good example of marginal cirque glaciation during GS-1 and the importance of local topography and microclimate for sustaining glaciers in some mountain areas of Britain and Ireland.

One would expect similarities between the Wicklow situation and that of Wales -- and indeed there are a number of known "late cirque glaciers" in Snowdonia (Eryri) and in the Brecon Beacons.   The only small glacier of equivalent age in Pembrokeshire was that of Cwm Cerwyn, close to Foelcwmcerwyn:

https://brian-mountainman.blogspot.com/2012/02/pembrokeshires-last-glacier.html

There are two other locations, both on the Preseli north face, where I think there might have been small Younger Dryas nivation hollows, firn fields or  mini-glaciers.  But the evidence is very subtle, as suggested in this post:

https://brian-mountainman.blogspot.com/2020/09/an-enigmatic-landform-on-north-slope-of.html