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

Abstract

Plateau icefields are a common form of mountain ice mass, frequently found in mid‐latitude to high‐arctic regions and increasingly recognized in the Quaternary record. Their top‐heavy hypsometry makes them highly sensitive to changes in climate when the equilibriaum line altitude (ELA) lies above the plateau edge, allowing ice to expand significantly as regional ELAs decrease, and causing rapid recession as climate warms. With respect to future climate warming, it is important to understand the controls on plateau icefield response to climate change in order to better predict recession rates, with implications for water resources and sea‐level rise. Improving knowledge of the controls on glacier recession may also enable further palaeoclimatic information to be extracted from the Quaternary glacial record. We use the distribution of moraines to examine topographic controls on Younger Dryas icefield recession in Scotland. We find that overall valley morphology influences the style of recession, through microclimatic and geometric controls, with bed gradient affecting moraine spacing. Ice mass reconfiguration may occur as recession progresses because ice divide migration could alter the expected response based on hypsometric distribution. These results add to a growing body of research examining controls on glacier recession and offer a step towards unravelling non‐linear ice mass behaviour. Copyright © 2019 John Wiley & Sons, Ltd.

Processes of ‘hummocky moraine’ formation in the Gaick, Scotland: insights into the ice‐marginal dynamics of a Younger Dryas plateau icefield

“…Geomorphologically, all the Younger Dryas moraines in the Gaick are organized as discrete chains of mounds and ridges that can be connected to form arcuate or chevronshaped patterns. The planform arrangement recognized in this study is thus comparable to that observed in many other areas of the Scottish Highlands Bennett & Boulton 1993a, b;Lukas 2003;Boston & Lukas 2019). Sedimentologically, the four moraine exposures reported here all yielded similar lithofacies associations and represent terrestrial ice-contact fans, with evidence for proglacial push, subglacial shearing and complete overriding in one case (moraine BCL-06).…”

“…In many cases, shallow meltwater channels (often <5 m deep) occur between the chains of moraines, conforming with the trend of the moraine arcs/chevrons down-slope. The morphological characteristics and spatial distribution of the Younger Dryas moraines in the Gaick closely resemble those of Younger Dryas moraines in other areas of upland Britain, where they have been interpreted as ice-marginal moraines and thus represent positions of individual palaeo-ice margins (Benn 1992;Benn et al 1992;Bennett & Boulton 1993a, b;McDougall 2001;Lukas 2003Lukas , 2005Boston & Lukas 2019).…”

“…The evidence for ice-marginal sedimentation in the form of terrestrial ice-contact fans, together with the dense spacing and planform arrangement of the moraine mounds and ridges (discontinuous arcs or chevronshaped chains), indicates that the Younger Dryas glaciers in the Gaick experienced active, oscillatory retreat that was punctuated by minor stillstands or re-advances, as has been documented at many Younger Dryas glaciers in Scotland (Benn 1992;Benn et al 1992;Bennett & Boulton, 1993a, b;Lukas 2003Lukas , 2005Finlayson et al 2011;Boston & Lukas 2019). Sedimentary evidence from moraine BCL-06, in the form of proglacial and subglacial glaciotectonism, indicates that a more substantial re-advance of the Gaick Glacier (Fig.…”

“…The planform arrangement recognized in this study is thus comparable to that observed in many other areas of the Scottish Highlands (Benn et al . ; Bennett & Boulton , b; Lukas ; Lukas & Benn ; Boston & Lukas ).…”

“…The morphological characteristics and spatial distribution of the Younger Dryas moraines in the Gaick closely resemble those of Younger Dryas moraines in other areas of upland Britain, where they have been interpreted as ice‐marginal moraines and thus represent positions of individual palaeo‐ice margins (Benn ; Benn et al . ; Bennett & Boulton , b; McDougall ; Lukas , ; Lukas & Benn ; Boston & Lukas ).…”