Deglaciation history and subsequent lake dynamics in the Siljan region, south‐central Sweden, based on new LiDAR evidence and sediment records

Möller, Per; Björck, Svante; Dowling, Thomas; Hammarlund, Dan; Ljung, Karl; Lund, Martin; Paradeisis‐Stathis, Savvas

doi:10.1002/esp.5471

Cited by 1 publication

(1 citation statement)

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“…It is therefore possible to envisage performing an interesting set of experiments within the instability model in the future, which includes variable sediment strength and thickness. However, if one is of the opinion that all drumlins are triggered by a bedrock obstacle, then the need for an instability‐based model may seem superfluous, as such forms do not require an instability to determine their location (e.g., Möller, 1987; Möller & Dowling, 2018). At the heart of this problem is whether drumlins are individual elements, each of which can arise and be explained on their own, or whether they are part of a spatially organized array with internal regularity.…”

Section: Discussionmentioning

confidence: 99%

Numerical modelling of subglacial ribs, drumlins, herringbones, and mega‐scale glacial lineations reveals their developmental trajectories and transitions

Ely

Stevens

Clark

et al. 2023

Earth Surf Processes Landf

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Initially a matter of intellectual curiosity, but now important for understanding ice‐sheet dynamics, the formation of subglacial bedforms has been a subject of scientific enquiry for over a century. Here, we use a numerical model of the coupled flow of ice, water, and subglacial sediment to explore the formation of subglacial ribs (i.e., ribbed moraine), drumlins and mega‐scale glacial lineations (MSGLs). The model produces instabilities at the ice–bed interface, which result in landforms resembling subglacial ribs and drumlins. We find that a behavioural trajectory is present. Initially subglacial ribs form, which can either develop into fields of organized drumlins, or herringbone‐type structures misaligned with ice flow. We present potential examples of these misaligned bedforms in deglaciated landscapes, the presence of which means caution should be taken when interpreting cross‐cutting bedforms to reconstruct ice flow directions. Under unvarying ice flow parameters, MSGLs failed to appear in our experiments. However, drumlin fields can elongate into MSGLs in our model if low ice–bed coupling conditions are imposed. The conditions under which drumlins elongate into MSGLs are analogous to those found beneath contemporary ice streams, providing the first mechanism, rather than just an association, for linking MSGLs with ice stream flow. We conclude that the instability theory, as realized in this numerical model, is sufficient to explain the fundamental mechanics and process‐interactions that lead to the initiation of subglacial bedforms, the development of the distinctive types of bedform patterns, and their evolutionary trajectories. We therefore suggest that the first part of the longstanding ‘drumlin problem’ – how and why they come into existence – is now solved. However, much remains to be discovered regarding the exact sedimentary and hydrological processes involved.

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Section: Discussionmentioning

confidence: 99%