Ice-contact lakes modify glacier geometry and dynamics by shifting the majority of mass loss from the ice surface to the terminus. Lake-terminating glaciers are known to experience greater thinning rates and higher velocities than land-terminating glaciers, but the controls on variability in surface elevation change and ice flow between lake-terminating glaciers in different regions remain poorly explored. We combined existing datasets of glacier velocity, surface elevation change and glacial lake area to characterise the evolution of 352 lake-terminating and land-terminating glaciers within three Himalayan sub-regions between 2000 and 2019. These analyses show that the influence of ice-contact lakes propagates up-glacier across only the lowermost 30% of the hypsometric distribution, even where lakes are well established. We find that ice-contact lakes only affect glacier behaviour when the lakes reach an advanced evolutionary stage; most clearly manifested in the Eastern Himalaya by statistically robust differences in glacier-wide surface elevation change between lake-terminating (–0.68 ± 0.05 m a–1) and land-terminating (–0.54 ± 0.04 m a–1) glaciers. These differences are driven by the presence of a greater number of well-developed ice-contact lakes in the Eastern Himalaya compared to in the Western and Central Himalaya, resulting from greater mass loss rates to date.

The Jostedalsbreen ice cap is mainland Europe's largest ice cap and accommodates 20% (458 km2 in 2019) of the total glacier area of mainland Norway. Jostedalsbreen and its meltwater contribute to global sea-level rise and to local water management, hydropower and tourism economies and livelihoods. In this study, we construct a digital terrain model (DTM) of the ice cap from 1966 aerial photographs, which by comparing to an airborne LiDAR DTM from 2020, we compute changes in surface elevation and geodetic mass balances. The area mapped in both surveys cover about 3/4 of the ice cap area and 49 of 82 glaciers. The measured glacier area has decreased from 363.4 km2 in 1966 to 332.9 km2 in 2019, i.e. a change of −30 km2 or −8.4% (−0.16% a−1), which is in line with the percentage reduction in area for Jostedalsbreen as a whole. The mean geodetic mass balance over the 49 glaciers was −0.15 ± 0.01 m w.e. a−1, however, large variability is evident between glaciers, e.g. Nigardsbreen (−0.05 m w.e. a−1), Austdalsbreen (−0.28 m w.e. a−1) and Tunsbergdalsbreen (−0.36 m w.e. a−1) confirming differences also found by the glaciological records for Nigardsbreen and Austdalsbreen.

We present the first systematic inventory of surge-type glaciers for the whole of Greenland compiled from published datasets and multitemporal satellite images and digital elevation models. The inventory allows us to define the spatial and climatic distribution of surge-type glaciers and to analyse the timing of surges from 1985 to 2019. We identified 274 surge-type glaciers, an increase of 37% compared to previous work. Mapping surge-type glacier distribution by temperature and precipitation variables derived from ERA5-Land reanalysis data shows that the west and east clusters occur in well-defined climatic envelopes. Analysis of the timing of surge active phases during the periods ~1985 to 2000 (T1) and ~2000 to 2019 (T2) suggests that overall surge activity is similar in T1 and T2, but there appears to be a reduction in surging in the west cluster in T2. Our climate analysis shows a coincident increase in mean annual and mean winter air temperature between T1 and T2. We suggest that as glaciers thin under current warming, some surge-type glaciers in the west cluster may be being prevented from surging due to (1) their inability to build-up sufficient mass and (2) a switch from a polythermal to a largely cold-based thermal regime.

Turbulent fluxes make a substantial and growing contribution to the energy balance of ice surfaces globally, but are poorly constrained owing to challenges in estimating the aerodynamic roughness length (z0). Here, we used structure from motion (SfM) photogrammetry and terrestrial laser scanning (TLS) surveys to make plot-scale 2-D and 3-D microtopographic estimations of z0 and upscale these to map z0 across an ablating mountain glacier. At plot scales, we found spatial variability in z0 estimates of over two orders of magnitude with unpredictable z0 trajectories, even when classified into ice surface types. TLS-derived surface roughness exhibited strong relationships with plot-scale SfM z0 estimates. At the glacier scale, a consistent increase in z0 of ~0.1 mm d−1 was observed. Space-for-time substitution based on time since surface ice was exposed by snow melt confirmed this gradual increase in z0 over 60 d. These measurements permit us to propose a scale-dependent temporal z0 evolution model where unpredictable variability at the plot scale gives way to more predictable changes of z0 at the glacier scale. This model provides a critical step towards deriving spatially and temporally distributed representations of z0 that are currently lacking in the parameterisation of distributed glacier surface energy balance models.

Fine resolution topographic data derived from methods such as Structure from Motion (SfM) and Multi-View Stereo (MVS) have the potential to provide detailed observations of geomorphological change, but have thus far been limited by the logistical constraints of conducting repeat surveys in the field. Here, we present the results from an automated time-lapse camera array, deployed around an ice-marginal lake on the western margin of the Greenland ice sheet. Fifteen cameras acquired imagery three-times per day over a 426 day period, yielding a dataset of ~19 000 images. From these data we derived 18 point clouds of the ice-margin across a range of seasons and successfully identified calving events (ranging from 234 to 1475 m2 in area and 815–8725 m3 in volume) induced by ice cliff undercutting at the waterline and the collapse of spalling flakes. Low ambient light levels, locally reflective surfaces and the large survey range hindered analysis of smaller scale ice-margin dynamics. Nevertheless, this study demonstrates that an integrated SfM-MVS and time-lapse approach can be employed to generate long-term 3-D topographic datasets and thus quantify ice-margin dynamics at a fine spatio-temporal scale. This approach provides a template for future studies of geomorphological change.

Processes and mechanisms of erosion, transport and deposition within high-magnitude outburst floods such as jökulhlaups and lahars are poorly understood and remain largely unquantified. This study therefore applies a two-dimensional or depth-averaged hydrodynamic model, with fully integrated sediment transport, to reconstruct a Holocene jökulhlaup to have occurred from Kverkfjöll volcano, Iceland. Results indicate simultaneous inundation of multiple channels, flow around islands, hydraulic jumps and multi-directional flow including backwater areas and hydraulic ponding. These flow characteristics are typical of outburst floods that are volcanically triggered, flow through steep volcanic terrain and contain high concentrations of volcaniclastic sediment. Kverkfjöll jökulhlaups had low frontal flow velocities but as stage increased, velocities reached 5–15ms–1. Peak stage was prolonged in zones of hydraulic ponding, but generally attenuated in magnitude and duration downstream. Suspended load transport persisted over the entire hydrograph but bed load transport was spatially discontinuous and comprised distinct pulses. A hierarchy of landforms is proposed, ranging from highest energy zones (erosional gorges, scoured bedrock, cataracts and spillways) to lowest (valley-fills, bars and slackwater deposits). Bedrock erosion was generally where flow exceeded ∽3m flow depth, ∽7ms–1 flow velocity, ∽1×102Nm–2 shear stress and 3 ×102Wm–2 stream power. Deposition occurred below ∽8m flow depth, 11 ms–1 flow velocity, 5 ×102Nm–2 shear stress and 3 ×103Wm–2 stream power. Hydraulic ranges associated with erosion and deposition have considerable overlap due to transitional flow phenomena, transitions in sediment concentration and the influence of upstream effects, such as hydraulic ponding behind topographic constrictions. These results are the first of coupled hydraulic and sediment transport phenomena in high-magnitude outburst floods with fluid rheology and high sediment content, such as jökulhlaups and dilute lahars. Modelled changes in sediment mass closely resembled field-mapped zones of erosion and deposition. This paper therefore introduces a capability to simulate rapid landscape change due to high-magnitude outburst flood.

Virtually no information is available on the response of land-terminating Antarctic Peninsula glaciers to climate change on a centennial timescale. This paper analyses the topography, geomorphology and sedimentology of prominent moraines on James Ross Island, Antarctica, to determine geometric changes and to interpret glacier behaviour. The moraines are very likely due to a late-Holocene phase of advance and featured (1) shearing and thrusting within the snout, (2) shearing and deformation of basal sediment, (3) more supraglacial debris than at present and (4) short distances of sediment transport. Retreat of ~100 m and thinning of 15–20 m has produced a loss of 0.1 km3 of ice. The pattern of surface lowering is asymmetric. These geometrical changes are suggested most simply to be due to a net negative mass balance caused by a drier climate. Comparisons of the moraines with the current glaciological surface structure of the glaciers permits speculation of a transition from a polythermal to a cold-based thermal regime. Small land-terminating glaciers in the northern Antarctic Peninsula region could be cooling despite a warming climate.

Jökulhlaups in 2007 and 2008 from an ice-dammed lake at the northern margin of Russell Glacier, West Greenland, marked the onset of a renewed jökulhlaup cycle after 20 years of stability. We present a record of successive ice-dammed lake drainage events and associated ice-margin dynamics spanning ∼25 years. Robust calculations of lake volumes and peak discharges are made, based on intensive field surveys and utilizing high-spatial-resolution orthophotographs of the lake basin and ice margin. These data enable identification of controls on the behaviour of the ice-dammed lake and provide the first field-based examination of controls on jökulhlaup magnitude and frequency for this system. We find that Russell Glacier jökulhlaups have a much higher peak discharge than predicted by the Clague–Mathews relationship, which we attribute to an unusually short englacial/subglacial routeway and the presence of a thin ice dam that permits incomplete sealing of jökulhlaup conduits between lake drainage events. Additionally, we demonstrate that the passage of jökulhlaups through an interlinked system of proglacial bedrock basins produces significant attenuation of peak discharge downstream. We highlight that improved understanding of jökulhlaup dynamics requires accurate information about ice-dammed lake volume and ice-proximal jökulhlaup discharge.

Recent topographical and ground-penetrating radar (GPR) surveys of Kårsaglaciären, which is a small (<1 km2) and thin (<56 m) mountain glacier in Arctic Sweden, show that there are small areas of temperate ice in the lowermost part of the glacier. This is curious because we would expect such a small and thin glacier to have a fully cold ablation zone. Specifically, with our analyses of present glacier geometry and thickness and of the prevailing climate, we are unable to explain the presence of temperate ice within the snout of Kårsaglaciären using prevailing models of glacier thermal structure. This leads us to suggest that the presence of temperate ice within Kårsaglaciären is a remnant of a previous polythermal state that existed when the glacier was larger and thicker. Kårsaglaciären is thus out of synch with current geometry and climate and is exhibiting a ‘thermal lag’. We propose that, with time, Kårsaglaciären’s ablation zone and perhaps the entire glacier may well become fully cold as the temperate zone shrinks further. We anticipate that such a thermal lag is likely to be present within other Arctic glaciers. A thermal lag and an evolution to a fully cold thermal state have significant implications for the dynamic behaviour of small Arctic glaciers and for meltwater production from them.

Measurements of glacier ice cliff evolution are sparse, but where they do exist, they indicate that such areas of exposed ice contribute a disproportionate amount of melt to the glacier ablation budget. We used Structure from Motion photogrammetry with Multi-View Stereo to derive 3-D point clouds for nine ice cliffs on Khumbu Glacier, Nepal (in November 2015, May 2016 and October 2016). By differencing these clouds, we could quantify the magnitude, seasonality and spatial variability of ice cliff retreat. Mean retreat rates of 0.30–1.49 cm d−1 were observed during the winter interval (November 2015–May 2016) and 0.74–5.18 cm d−1 were observed during the summer (May 2016–October 2016). Four ice cliffs, which all featured supraglacial ponds, persisted over the full study period. In contrast, ice cliffs without a pond or with a steep back-slope degraded over the same period. The rate of thermo-erosional undercutting was over double that of subaerial retreat. Overall, 3-D topographic differencing allowed an improved process-based understanding of cliff evolution and cliff-pond coupling, which will become increasingly important for monitoring and modelling the evolution of thinning debris-covered glaciers.