Abstract. We report three active subglacial lakes within 2 km of the lateral margin of Isunguata Sermia, West Greenland, identified by differencing time-stamped ArcticDEM strips. Each lake underwent one drainage–refill event between 2009 and 2017, with two lakes draining in < 1 month in August 2014 and August 2015. The 2015 drainage caused a ∼ 1-month down-glacier slowdown in ice flow and flooded the foreland, aggrading the proglacial channel by 8 m. The proglacial flooding confirms the ice-surface elevation anomalies as subglacial water bodies and demonstrates how their drainage can significantly modify proglacial environments. These subglacial lakes offer accessible targets for geophysical investigations and exploration.

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 on limited sedimentary exposures, coring and surface geomorphic evidence. We report an extensive (42 km of data within a 24-km 2 study area) and deep (reflections recorded at depths up to 100 m) lowfrequency (40 and 100 MHz) ground-penetrating radar (GPR) survey of the Sandg ıgur moraines, SE Iceland. GPR profiles reveal a much larger (67 m high) and extensive (1.25 km wide) buried moraine ridge than that suggested by surface topography (typically 125 m wide and 7 m high). These data reveal that the Sandg ıgur moraines was deposited during a major Holocene re-advance of Skeiðar arj€ okull. The moraine ridge is buried by sediments dominated by glacifluvial deposits with an estimated sediment volume of 1.04 km 3 . We combine GPR-derived subsurface architecture and the surface morphology to develop a conceptual model detailing the geomorphic evolution of the moraine and surrounding region. These results provide new insights into the Holocene evolution of Skeiðar arsandur, identifying the presence of a former major ice-margin position, as well as a past relative sea-level limit. Furthermore, we establish that sediment supply and available terrestrial accommodation space are dominant drivers in the formation and evolution of vast sandar environments.

How landscapes respond to, and evolve from, large jökulhlaups (glacial outburst floods) is poorly constrained due to limited observations and detailed monitoring. We investigate how melt of glacier ice transported and deposited by multiple jökulhlaups during the 2010 eruption of Eyjafjallajökull, Iceland, modified the volume and surface elevation of jökulhlaup deposits. Jökulhlaups generated by the eruption deposited large volumes of sediment and ice, causing significant geomorphic change in the Gígjökull proglacial basin over a 4-week period. Observation of these events enabled robust constraints on the physical properties of the floods which informs our understanding of the deposits. Using ground-based LiDAR, GPS observations and the satellite-image-derived ArcticDEMs, we quantify the post-depositional response of the 60 m-thick Gígjökull sediment package to the meltout of buried ice and other geomorphic processes. Between 2010 and 2016, total deposit volume reduced by −0.95 × 106 m3 a−1, with significant surface lowering of up to 1.88 m a−1. Surface lowering and volumetric loss of the deposits is attributed to three factors: (i) meltout of ice deposited by the jökulhlaups; (ii) rapid melting of the buried Gígjökull glacier snout; and (iii) incision of the proglacial meltwater system into the jökulhlaup deposits.

Various field operators and developers in the Eastern Mediterranean are reliant on the development of export pipeline routes that ascend the eastern portion of the Nile submarine delta. Evidence of numerous complex slope instability events and other geohazard processes across the submarine delta front mean that risk mitigation in this region needs careful considerationprior to installation. This paper focuses on integrated site characterisation including detailed sedimentological logging and two-dimensional (2D) geomechanical modelling of slope stability for a recent project on the eastern portion of the Nile submarine delta, with focus on four distinct palaeolandslide features on the delta slope region. Based on the review and integration of geophysical, geological and geotechnical datasets, all four palaeolandslides appear to have failed in a translational manner along a shear surface at approximately 6 m below seafloor. The shear surface coincides with the presence of a strong impedance reflector mapped in sub-bottom profiler data. This reflectorcorrelates well with a sampled occurrence of an approximately 1 m-thick silty sand bed (sedimentological FaciesN2), bounded above and below by extremely low to very low strength organic clay sediments (Facies N1). Eleven radiocarbon tests were performed in the palaeolandslide evacuation surfaces and the resultant mass transport deposits. These test resultsindicate that the four events occurred between approximately 500 years and 1600 years before present, with a best estimate age of 800 years before present (i.e. 12th century AD). The 1068 AD Gulf of Aqaba earthquake or the 1202 AD Lebanon earthquake are possible triggers for the palaeolandslides and relict seafloor morphology. Deterministic 2D slope stability analyses were performed along four slope profiles to output values for factor of safety (FOS) against slope failure. The analyses modelled present-day slope stability, and a reconstructed (pre-failure) seafloor to further understand the characteristics of the four observed palaeolandslides. The modelling showed that the slopes are stable under presentday conditions, even under abnormal level event (ALE) seismic loading. The modelling also showed how faulting plays a key part in overall slope stability: some faults buttress upslope sediments and thus increase the slope FOS, whereas in other casesthe faults steepen the overall slope and result in a lower slope FOS. The key uncertainty in the slope stability modelling is the poorly understood lateral geotechnical variability of Facies N2, which variesfrom silty fine sand to sandy silt, and the complex and currently uncharacterised behaviour of Facies N2 under cyclic seismic loading. It is possible that the variable fines content governs whether Facies N2 behaves in a drained or undrained mannerduring seismic loading, and how much strength degradation (i.e. liquefaction) may occur. All these factors could contribute to the stability of the slope during earthquake loading.

&lt;p&gt;The sedimentary record of Icelandic ice-contact environments provides valuable information about 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 on limited sedimentary exposures and surface geomorphic evidence. Although geophysical surveys of Icelandic sandur have been conducted, they have often been of limited spatial scale and focus on specific landforms. We report an extensive (42 km of data within a 24 km&lt;sup&gt;2 &lt;/sup&gt;study area) and detailed (reflections recorded at depths of up to 100 m) low-frequency (40 and 100 MHz) Ground-Penetrating Radar (GPR) survey of the Sandg&amp;#237;gur moraine complex, SE Iceland. This transforms our understanding of this landform, with implications for the Holocene glacial history and evolution of Skei&amp;#240;ar&amp;#225;rsandur and SE Iceland.&lt;/p&gt;&lt;p&gt;The Sandg&amp;#237;gur moraines are located on Skei&amp;#240;ar&amp;#225;rsandur, SE Iceland, down-sandur of large Little Ice Age-moraines of Skei&amp;#240;ar&amp;#225;rj&amp;#246;kull. They have a relatively subtle surface geomorphic expression (typically 7 m high and 125 m wide), and knowledge of their formation is limited, with no dating control on their age or detailed geomorphic or sedimentological investigations. GPR-data reveals reflections interpreted as large progradational foresets (dip angle: 2.19&amp;#176; &amp;#8211; 6.87&amp;#176;) beneath the morainic structure (depth of 100 m). These features are consistent with a sub-aqueous depositional environment before moraine formation, providing potential indications of past relative sea-level limits. GPR profiles in the vicinity of the Sandg&amp;#237;gur moraines reveal a much larger (67 m high and 1.25 km wide) and extensive buried moraine complex than that suggested by surface morphology. Indicating that the moraine was a major Holocene ice margin of Skei&amp;#240;ar&amp;#225;rj&amp;#246;kull. The buried Sandg&amp;#237;gur moraine ridge is comprised of a unit of chaotic folded reflections adjacent to a unit of parallel, down-sandur dipping reflections (dip angle: 1.29&amp;#176; &amp;#8211; 2.27&amp;#176;) indicative of an ice-contact or end-moraine fan. Possible evidence of buried ice at depth is also present within radargrams surrounding the moraine ridges. Sediment above the morainic bounding surface is interpreted to be dominated by glaciofluvial deposits with an estimated sediment volume of 1.04 km&lt;sup&gt;3&lt;/sup&gt; over the 24 km&lt;sup&gt;2&lt;/sup&gt; study area. Potential moraine breaches, possibly caused by high magnitude j&amp;#246;kulhlaups (glacier outburst floods) are coincident within the GPR data and the surface geomorphology.&lt;/p&gt;&lt;p&gt;We combine GPR-derived subsurface architecture with the current surface morphology to develop a conceptual model detailing the geomorphic evolution of the moraines and surrounding region, from pre-moraine morphology, to their formation and burial, resulting in the present-day morphology. These results provide new insights into the Holocene to present-day glacial history of Skei&amp;#240;ar&amp;#225;rj&amp;#246;kull and the controls on sedimentation responsible for the evolution of Skei&amp;#240;ar&amp;#225;rsandur, with implications for the formation of sandar environments and the Holocene environmental history of SE Iceland.&lt;/p&gt;