A Younger Dryas plateau icefield in the Monadhliath, Scotland, and implications for regional palaeoclimate

Abstract

a b s t r a c tA record of Younger Dryas glaciation in Scotland is well established. However, the role of the Monadhliath, a significant plateau area extending over 840 km 2 in central Scotland, has never been investigated systematically. We present the first systematic glacial geomorphological mapping across the whole region, which has led to the identification of hitherto-unrecorded glacial and associated landforms. The spatial distribution of these landforms indicates that the last phase of glaciation in the area was that of a local plateau icefield. In addition, a clear morphostratigraphical signature provides a strong indication that the icefield dates to the Younger Dryas (12.9e11.7 ka), which is supported by numerical ages in the southeast of the study area. Based on the geomorphological evidence and 2D glacier surface profile modelling, a 280 km 2 icefield is reconstructed. A novel approach is introduced to quantify plateau icefield thickness for equilibrium line altitude (ELA) and palaeoprecipitation calculations, resulting in greater overall data confidence compared to traditional reconstruction methods. The ELA for the whole icefield is calculated to be 714 ± 25 m, whilst the ELAs of individual outlet glaciers range from 560 m in the west to 816 m in the east, demonstrating a significant WeE precipitation gradient across the region during the Younger Dryas. These ELAs compare well with those calculated for Younger Dryas ice masses reconstructed in neighbouring regions and are in good agreement with overall precipitation patterns suggested for Scotland during this time. Whilst the total amount of precipitation calculated from these ELAs is highly dependent on the method used, irrespective of this, the study suggests a more arid Younger Dryas climate in the region compared to the present day.

Younger Dryas glaciers and climate in the Mourne Mountains, Northern Ireland

“…Unfortunately, although independent palaeoenvironmental proxies indicate cooling, landscape instability and the expansion of arctic shrub tundra in Ireland during the Younger Dryas (Watson et al ., ; Walker et al ., ), there is little information about precipitation during this period against which to validate these inferences. Despite this, the precipitation values reported here are comparable to those reconstructed for the Younger Dryas in parts of central and western Scotland (table 5 in Boston et al ., ), but generally lower than for parts of NW Wales (table in Bendle and Glasser, ).…”

Topographic controls on plateau icefield recession: insights from the Younger Dryas Monadhliath Icefield, Scotland

“…Topographic map of the Monadhliath study area, including reconstruction of the Younger Dryas Monadhliath Icefield (Boston et al ., ). [Color figure can be viewed at wileyonlinelibrary.com]…”

“…). ELAs calculated using an area‐altitude balance ratio of 1.9 ± 0.81 (Rea, ) range between 560–646 m in the west and 738–814 m in the east, demonstrating a precipitation gradient across the area (Boston et al ., ). All ELAs are located either on the plateau ice surface or on the valley backwall close to the plateau edge, meaning the icefield would have been sensitive to small fluctuations in climate.…”

The glacial geomorphology of the Loch Lomond (Younger Dryas) Stadial in Britain: a review

“…It is possible that the features formed early during this period, particularly given that a two‐ (or three‐) phase LLS has been inferred at other locations based upon moraine distribution patterns (e.g. Benn et al ., ; Brown et al ., ; Boston et al ., ). Numerical modelling by Golledge et al .…”

“…Geomorphological mapping of Gleann Ballach and Gleann Fionndrigh (adapted from Boston et al ., ). A morphostratigraphic approach was used to determine the limits of LLS glaciation.…”