Reconstruction of Loch Lomond Stadial (Younger Dryas) glaciers on Ben More Coigach, north-west Scotland, and implications for reconstructing palaeoclimate using small ice masses

Abstract

A significant inventory of evidence exists for Loch Lomond Stadial (LLS; ≈Younger Dryas) glaciation in Scotland, with recent work focused on satellite icefields. However, studies of more marginal settings are important for assessing the influence of topoclimatic factors on glacier functioning and, crucially, the impact of these on glacier‐derived palaeoclimatic reconstructions. We present systematic assessments of snowblow and avalanching contributions, informed by modern analogues, and test these using the first detailed palaeoglaciological reconstructions of three corrie glaciers on Ben More Coigach, north‐west Scotland. Based on morphostratigraphic principles, and lithostratigraphic evidence from the region, these have been attributed to the LLS, with the reconstructions yielding an average equilibrium‐line altitude (ELA) of 328 ± 16 m. A glacier‐derived sea‐level equivalent precipitation value of 1903 ± 178 mm a−1 is inferred for the LLS, suggesting wetter conditions than currently and contradicting assertions of a more arid LLS climate. Comparison with published palaeoprecipitation estimates indicates Ben More Coigach does not conform to expected regional precipitation gradients. We argue that these discrepancies reflect topographically enhanced snow accumulation, which lowered the ELA from the ‘true’ climatic ELA. This highlights the importance of assessing the influence of topoclimatic factors when applying small glaciers in palaeoclimatic reconstructions.

A spatially-restricted Younger Dryas plateau icefield in the Gaick, Scotland: Reconstruction and palaeoclimatic implications

“…snowblow, avalanching, topographic shading) can play an important role in augmenting glacier mass balance and lowering ELAs (e.g. Sissons and Sutherland, 1976;Mitchell, 1996;Nesje and Dahl, 2000;Coleman et al, 2009;Mills et al, 2009Mills et al, , 2012Chandler and Lukas, 2017). Previous Scottish studies have shown that an eastward decline in ELAs is a characteristic feature of many Younger Dryas icefields, including the neighbouring Drumochter Icefield.…”

“…7 and 9), snow may have been transferred to the former glacier surface through snowblow from the plateau, thereby augmenting glacier mass balance and lowering the ELA (cf. Coleman et al, 2009;Mills et al, 2009Mills et al, , 2012Chandler and Lukas, 2017). In addition, the Glas Glacier catchment contains a substantial basin -one of the few well-developed cirques in the area -that could have allowed the preferential accumulation of snow from snow-bearing winds from the northwest to north.…”

“…An alternative temperature function has been advocated by Golledge et al (2010) that incorporates the effect of local glacier cooling, but this has not been used as (i) it would preclude direct comparison with previously-published work from Scotland and (ii) it is not possible to account for the effect of glacier cooling on air temperature for the Gaick Icefield as a whole (cf. Boston et al, 2015;Chandler and Lukas, 2017). Following procedures outlined by Boston et al (2015), and applying the palaeotemperature value of 3.5 ± 1.0 °C to the P/T functions, yielded palaeoprecipitation estimates of 1795 ± 539 mm a -1 using the Ohmura et al (1992) equation, and 1763 ± 657, 1260 ± 527 and 1008 ± 461 mm a -1 for the summer-, neutral-and winter-types, respectively, using the Golledge et al (2010) equation (Table 5).…”

The glacial landsystem of a tropical glacier: Charquini Sur, Bolivian Andes

“…Examples of the range of landform-sediment assemblages have been provided for a number of modern and palaeoglacial environments, including in low-latitude (e.g. Benn, 1989;Kirkbride, 2000;Glasser and Hambrey, 2002;Deline and Orombelli, 2005;Roberson, 2008;Burki et al, 2009;Lukas, 2012;Bendle and Glasser, 2012;Chandler and Lukas, 2017), and high-latitude (e.g. Benn, 1989;Kirkbride, 2000;Glasser and Hambrey, 2002;Deline and Orombelli, 2005;Roberson, 2008;Burki et al, 2009;Lukas, 2012;Bendle and Glasser, 2012;Chandler and Lukas, 2017), and high-latitude (e.g.…”

“…Benn and Owen, 2002;Owen et al, 2003), mid-latitude (e.g. Benn, 1989;Kirkbride, 2000;Glasser and Hambrey, 2002;Deline and Orombelli, 2005;Roberson, 2008;Burki et al, 2009;Lukas, 2012;Bendle and Glasser, 2012;Chandler and Lukas, 2017), and high-latitude (e.g. Fitzsimons, 2003;Glasser and Hambrey, 2003;Lukas et al, 2005;Evans et al, 2006aEvans et al, , 2016bEvans, 2010;Brynjólfsson et al, 2012) settings.…”