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A. ArcticDEM surface; red lines indicate the location of GPR profiles. B. Interpolated DEM of the RS1 surface. Black lines show the pick locations of RS1 within GPR profiles. C. DEM of difference showing sediment thickness between RS1 and the surface of the sandur. D–G. Elevation profiles of the subsurface ridge that characterizes RS1. Locations of the profiles can be seen in (A) and (B).
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The sedimentary record of Icelandic ice‐contact environments provides critical insights into past glacier margin dynamics and position, relative sea level, and the geomorphic processes that drive the evolution of proglacial environments. This important archive has been little exploited, however, with most glacier and sea‐level reconstructions based...
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... This geophysical method is particularly useful in areas where sediment exposures are lacking (e.g. Harrison et al., 2022;Pellicer & Gibson, 2011;Spagnolo et al., 2014) and has been used to investigate eskers in both modern and ancient glacial settings (Burke et al., 2008;Perkins et al., 2013Perkins et al., , 2016Stoker et al., 2021). ...
Directly observing glacial drainage systems (englacial and subglacial) is challenging. The distribution, morphology and internal structure of eskers can provide valuable information about the glacial drainage system and meltwater processes. This work presents the annual evolution (meltout) and internal structure of an esker emerging from the Breiðamerkurjökull ice-margin, southeast Iceland. Changes in esker morphology have been repeatedly mapped over a one-year period using high temporal and spatial resolution data acquired by an uncrewed aerial vehicle (UAV). The internal architecture of the esker was investigated using ground penetrating radar (GPR) surveys. These data are used to identify the dominant processes driving the formation of this englacial esker and to evaluate the preservation potential. The englacial esker was up to 2.6 m thick and ice-cored in origin. A large moulin upglacier of the esker, which evolved into an englacial conduit, supplied meltwater to the englacial channel. Upglacier dipping debris-filled basal hydrofractures, formed by pressurised subglacial meltwater rising up the retrograde bed slope, likely supplied sediment to the englacial conduit. Over the one-year period of observation the crest morphology evolved from flat- to sharp-crested and the esker footprint increased by a factor of 5.7 in response to post-depositional processes. The findings presented here indicate that englacial eskers may have low preservation potential due to post-depositional reworking such as slumping through ice core melt-out and erosion by later meltwater flow. As englacial eskers may not be preserved in the landscape, they could represent important glacial drainage system components that are not currently captured in palaeo-ice sheet reconstructions. This work highlights the value of creating a time-series of high temporal-resolution data to quantify morphological evolution and improve glacial process-form models.
... In western Skeiðarársandur, a large and partially buried icemarginal landsystem related to the Sandgígjur (alternatively known as 'Sandgígur' in historic maps and previous literature) moraines (Fig. 1) has been identified (Harrison et al., 2022). This moraine and associated ice-contact/end-moraine fan are hypothesised to represent a pre-LIA terminus position of Skeiðarárökull (Harrison et al., 2022). ...
... In western Skeiðarársandur, a large and partially buried icemarginal landsystem related to the Sandgígjur (alternatively known as 'Sandgígur' in historic maps and previous literature) moraines (Fig. 1) has been identified (Harrison et al., 2022). This moraine and associated ice-contact/end-moraine fan are hypothesised to represent a pre-LIA terminus position of Skeiðarárökull (Harrison et al., 2022). Surface and subsurface components of the Sandgígjur moraine indicate a maximum height of 67 m (based upon a radiowave velocity of 0.13 m − ns 1 ) (Harrison et al., 2022). ...
... This moraine and associated ice-contact/end-moraine fan are hypothesised to represent a pre-LIA terminus position of Skeiðarárökull (Harrison et al., 2022). Surface and subsurface components of the Sandgígjur moraine indicate a maximum height of 67 m (based upon a radiowave velocity of 0.13 m − ns 1 ) (Harrison et al., 2022). A total of approx. 1 km 3 of glaciofluvial sediment, associated to jökulhlaup events, has buried the moraine following glacier retreat (Harrison et al., 2022). ...
Sandur plains are extensive sedimentary bodies formed in proglacial settings by glaciofluvial processes. Icelandic sandar have been hypothesised to be comprised of thick alluvial successions that provide critical insight into the processes that contributed to their formation and evolution. However, to‐date, most sandar research has focused on the analysis of sedimentary successions associated to topographically‐confined and small‐scale systems. These, however, do not capture the variety or scale of processes that influence sandar architecture. Therefore, detailed subsurface analysis of large‐scale and unconfined sandar is vital to understand how these systems respond to fundamental drivers, such as: (i) glacier oscillations, and (ii) episodic sediment flux from glacier outburst floods (aka. jökulhlaups). We report an extensive, low‐frequency (40 & 100 MHz) ground‐penetrating radar (GPR) survey of the ice‐proximal component of a large‐scale () active sandur in southeast Iceland. A bright and continuous reflection (PR1) is identified within all radargrams and provides a boundary between pre‐LIA and LIA to present‐day sedimentation. GPR data reveals a ~50 m thick ice‐proximal sediment wedge that is attributed to jökulhlaup and surge‐related glaciofluvial activity during the Little Ice Age (LIA). An approximate rate of deposition of 0.2–0.65 m has been calculated for the sediment wedge above PR1. Furthermore, we propose an extensive, sandur‐wide, pre‐LIA ice marginal limit of Skeiðarárökull, southeast Iceland, based on observations reported here and in previous work.
... Interferometric synthetic aperture radar (InSAR) and persistent scatterer interferometry (Dini et al., 2019;Hooper et al., 2012;Li et al., 2015;Tofani et al., 2013) techniques have been used to investigate the stability of moraines and slopes around glacial lakes. Structure and seepage inside moraine dams have been studied using ground-penetrating radar, electrical resistivity tomography, and the self-potential method (Harrison et al., 2022;Rajaure et al., 2018;Thompson et al., 2012). Moraine dam research has transitioned from qualitative descriptions of dam morphology and internal structure to quantitative analyses that combine field observations, tests, and simulations. ...
... Moraine dam research has transitioned from qualitative descriptions of dam morphology and internal structure to quantitative analyses that combine field observations, tests, and simulations. Most qualitative analyses have focused on dam geometry (Fujita et al., 2013;Hu et al., 2020), surface morphology (Dini et al., 2019;Hooper et al., 2012;Li et al., 2015;Tofani et al., 2013), internal structure and seepage conditions (Harrison et al., 2022;Rajaure et al., 2018;Thompson et al., 2012). And some researches also addressed on dam failure mechanisms were initially based on laboratory experiments (Balmforth et al., 2008(Balmforth et al., , 2009) and subsequently focused on numerical simulations (Begam et al., 2018;Minussi & Maciel, 2012;Osti et al., 2011). ...
Permafrost degradation increases the likelihood of glacial lake outburst floods on the Tibetan Plateau. Analyses of the freeze–thaw conditions in moraine dams and associated impacts on dam stability contribute toward reducing natural hazard risks. We used the heat transfer module of COMSOL Multiphysics to simulate the soil temperature field in the Longbasaba moraine dam, which is on the northern slope of central Himalaya. There is close agreement between the simulated and observed soil temperature values. Root mean squared errors (the square root of the mean of the square of all of the error) are below 1.30°C and mean bias errors vary from −0.10 to −0.52°C for the different soil layers. Between 1959 and 2020, active layer thickness increased at a mean annual rate of 0.024 m a⁻¹. Under the Coupled Model Intercomparison Project Phase 6 scenarios, the buried ice inside the moraine dam is clearly melting. The maximum‐buried ice thaw depth is currently 3.4 m and at the end of the 21st century is projected to be 9.53, 16.69, and 21.83 m under SSP1‐2.6, SSP2‐4.5, and SSP5‐8.5, which indicates a continuous decrease in moraine dam stability.
