Small-scale recessional push moraines are a characteristic signature of the active temperate glacial landsystem, and are often clearly linked to annual re-advances. These recessional push moraines represent a potentially valuable terrestrial climate archive, and may provide valuable insights into glacier dynamics. This paper presents detailed glacial geomorphological maps of recessional push moraines on the foreland of Skálafellsjökull, SE Iceland. Geomorphological maps have been produced at a scale of 1:3750 based on 2006 aerial photographs and 2012 satellite imagery. Using unmanned aerial vehicle-captured imagery, large-scale sample mapping of two selected areas of the glacier foreland has also been conducted, with the maps reproduced as A4-sized figures at scales of ∼1:2500 and ∼1:2000, respectively. Desk- and field-based mapping reveals suites of recessional push moraines distributed across the glacier foreland, often found in close association with flutings. Moraines on the foreland typically display distinctive ‘sawtooth' planform geometries, with complexities in the pattern occurring due to localised superimposition. The inventory of glacial geomorphological maps presented here provides a framework for subsequently exploring the characteristics of the recessional push moraines and recent ice-marginal fluctuations at Skálafellsjökull.
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.
Geophysical surveys provide an efficient and non-invasive means of studying subsurface conditions in numerous sedimentary settings. In this study, we explore the application of three geophysical methods to a proglacial environment, namely ground penetrating radar (GPR), seismic refraction and multi-channel analysis of surface waves (MASW). We apply these geophysical methods to three glacial landforms with contrasting morphologies and sedimentary characteristics, and we use the various responses to assess the applicability and limitations of each method for these proglacial targets. Our analysis shows that GPR and seismic (refraction and MASW) techniques can provide spatially extensive information on the internal architecture and composition of moraines, but careful survey designs are required to optimise data quality in these geologically complex environments. Based on our findings, we define a number of recommendations and a potential workflow to guide future geophysical investigations in analogous settings. We recommend the initial use of GPR in future studies of proglacial environments to inform (a) seismic survey design and (b) the selection of seismic interpretation techniques. We show the benefits of using multiple GPR antenna frequencies (e.g., 25 and 100 MHz) to provide decimetre scale imaging in the near surface (e.g., < 15 m) while also enabling signal penetration to targets at up to ∼40 m depth (e.g., bedrock). This strategy helps to circumvent changes in radar signal penetration resulting from variations in substrate conductivity or abundant scatterers. Our study also demonstrates the importance of combining multiple geophysical methods together with ground-truthing through sedimentological observations to reduce ambiguity in interpretations. Implementing our recommendations will improve geophysical survey practice in the field of glacial geology and allow geophysical methods to play an increasing role in the interpretation of glacial landforms and sediments.
Small-scale recessional push moraines are a characteristic signature of the active temperate glacial landsystem, and are often clearly linked to annual re-advances. These recessional push moraines represent a potentially valuable terrestrial climate archive, and may provide valuable insights into glacier dynamics. This paper presents detailed glacial geomorphological maps of recessional push moraines on the foreland of Skálafellsjökull, SE Iceland. Geomorphological maps have been produced at a scale of 1:3750 based on 2006 aerial photographs and 2012 satellite imagery. Using unmanned aerial vehicle-captured imagery, large-scale sample mapping of two selected areas of the glacier foreland has also been conducted, with the maps reproduced as A4-sized figures at scales of ∼1:2500 and ∼1:2000, respectively. Desk- and field-based mapping reveals suites of recessional push moraines distributed across the glacier foreland, often found in close association with flutings. Moraines on the foreland typically display distinctive 'sawtooth' planform geometries, with complexities in the pattern occurring due to localised superimposition. The inventory of glacial geomorphological maps presented here provides a framework for subsequently exploring the characteristics of the recessional push moraines and recent ice-marginal fluctuations at Skálafellsjökull.
Many glaciated valleys in Scotland contain distinctive, closely spaced ridges and mounds, which have been termed 'hummocky moraine'. The ridges and mounds are widely interpreted as ice-marginal moraines, constructed during active retreat of mainly temperate glaciers. However, hummocky terrain can form by various processes in glacial environments, and it may relate to a range of contrasting glaciodynamic regimes. Thus, detailed geomorphological and sedimentological studies of hummocky surfaces in Scottish glaciated valleys are important for robust interpretations of former depositional environments and glacier dynamics. In this contribution, we examine irregularly shaped ridges and mounds that occur outside the limits of former Loch Lomond Readvance (≈ Younger Dryas; ~ 12.9–11.7 ka) glaciers in the Gaick, Central Scotland. These ridges and mounds are intimately associated with series of sinuous channels, and their planform shape mimics the form of the adjacent channels. Available exposures through ridges in one valley reveal that those particular ridges contain lacustrine, subglacial, and glaciofluvial sediments. The internal sedimentary architecture is not related to the surface morphology; thus, we interpret the irregularly shaped ridges and mounds as erosional remnants (or interfluves). Based on the forms and spatial arrangement of the associated channels, we suggest that the ridges and mounds were generated by a combination of ice-marginal and proglacial glaciofluvial incision of glaciogenic sediments. The evidence for glaciofluvial incision, rather than ice-marginal moraine formation, at pre-Loch Lomond Readvance glacier margins in the Gaick may reflect differences in glaciodynamic regimes and/or efficient debris delivery from the glacier margins to the glaciofluvial systems.
<p>Recently deglaciated forelands contain a wealth of geomorphological and sedimentological data that can provide key information about glacier-climate relationships. Mountain glaciers are particularly important indicators of climate change due to their short response times, which means that their forelands provide a sub-decadal record of changes in glacier size and climate-related dynamics. In this contribution, we examine the glacial geomorphological and sedimentological record at &#216;stre Svartisen, an Arctic plateau icefield in Norway, and discuss temporal variations in glacier dynamics and processes of sediment deposition in response to climate warming since the Little Ice Age (c.1750). We focus specifically on the northeastern sector of the icefield and include two separate cirque/valley glaciers immediately to the north. Differences in landform-sediment assemblages are apparent both within and between forelands relating to changes in topography as well as glacier dynamics. Satellite images and old aerial photographs are also used to investigate differences in the rates of glacier demise across the study area. This evidence enables links to be made between landform generation, bed morphology, glacier dynamics, and glacier response to climate change, which furthers understanding of plateau icefield and outlet glacier behaviour in a warming climate.</p>
Abstract Topography exerts a strong control on how glaciers respond to changes in climate. Increased understanding of this role is important for both refining model predictions of future rates of glacier recession and for reconstructing climatic change from the glacial geological record. In this paper, we examine the geomorphological and sedimentological evidence in the foreland of Fingerbreen, a temperate outlet of the plateau icefield Østre Svartisen. The aim is to investigate the relationship between processes of landform generation and the changing influence of topography as recession progressed. The Fingerbreen foreland is dominated by bouldery Little Ice Age moraines and extensive areas of striated bedrock. A heavily fluted zone occurs in the central part of the foreland that is cross‐cut by annual transverse and sawtooth moraines. Systematic investigations of the structural architecture of moraines at various locations in the foreland provide evidence for a range of moraine‐forming processes, which can be linked to the topographic setting (e.g. deposition on a reverse bedrock slope) and drainage conditions. This includes push and bulldozing of proglacial sediments and squeezing of sub‐glacial sediments and submarginal freeze‐on of sediment slabs. We also identify variations in moraine spacing as a result of topography. This research demonstrates the importance of topography when interpreting moraine records in the context of climate and glacier dynamics.
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