Britain and Ireland: Glacial landforms during the Bølling–Allerød Interstadial

The Bølling–Allerød Interstadial is known as the Windermere and Woodgrange Interstadials (sometimes simply as the Late-glacial Interstadial) in Britain and Ireland, respectively, and is correlated with Greenland Interstadial 1. This was a period of significant climatic amelioration with an expansion of pioneer shrub and tree species, notably juniper and birch. Climatic reconstructions suggest that peak summer temperatures were warmer than today although the climate was more continental with a greater annual range between winter and summer, accompanied by drier conditions than today. Overall, the interstadial was characterised by negative glacier mass balance and significant reductions in glacier extents across Britain and Ireland. However, it is unknown whether glaciers disappeared entirely. In eastern Scotland, there is evidence that marine ice retreat occurred as late as 13.5ka, although dating evidence is limited. Others have argued for an ice expansion late in the interstadial into the Younger Dryas Stadial (Loch Lomond Stadial in Britain), although the evidence for this is disputed. Dating the glacier successions through the interstadial in Britain and Ireland has proven to be notoriously difficult, in part due to the removal of Late-glacial deposits by subsequent ice growth during the Loch Lomond Stadial, whilst the geochronological evidence associated with glacial records for this interval are often inconclusive.