Reconstruction of a Lateglacial (Younger Dryas) mountain ice field in Sutherland, Northwestern Scotland, and its palaeoclimatic implications

Quaternary geomorphological and geological mapping of a large area (∼1800 km2) in the northwestern Scottish Highlands has led to the reconstruction of a coherent mountain ice field approximately 45 km long and 30 km wide at its maximum extent. This West Sutherland ice field covered an area of ∼350 km2 and had a mean equilibrium-line altitude of 334 m, assuming that the outlet glaciers all reached their maxima simultaneously. Numerical dating strongly suggests a Younger Dryas (12.9–11.7 ka) age of the mapped limits of this mountain ice field. This study also shows that the area of northwestern Scotland covered by Younger Dryas glaciers was five times larger than previously thought. Palaeo-temperature estimates, obtained from chironomid and beetle assemblages elsewhere, have been used to reconstruct palaeo-precipitation during the Younger Dryas for west Sutherland. Using a previously published global empirical dataset, annual precipitation of 2344 ± 248 mm a−1 at sea level is inferred from our new palaeo-glacier reconstruction, suggesting slightly wetter conditions compared to the present day. These figures are in good agreement with those reconstructed for other parts of the Scottish Highlands and Islands, and this may indicate a marked W–E palaeo-precipitation gradient during the Younger Dryas. This paper goes on to discuss the wider validity of palaeo-climatic reconstructions from inferred palaeo-glacier geometries and presents a number of possible Scottish Lateglacial climate scenarios which warrant further testing.