Glacier Snout Research Articles

Multitemporal characterization of a proglacial system: a multidisciplinary approach

Abstract. The recession of Alpine glaciers causes an increase in the extent of proglacial areas and leads to changes in the water discharge and sediment balance (morphodynamics and sediment transport). Although the processes occurring in proglacial areas are relevant not only from a scientific point of view but also for the purpose of climate change adaptation, there is a lack of work on the continuous monitoring and multitemporal characterization of these areas. This study offers a multidisciplinary approach that merges the contributions of different scientific disciplines, such as hydrology, geophysics, geomatics, and water engineering, to characterize the Rutor Glacier and its proglacial area. Since 2020, we have surveyed the glacier and its proglacial area using both uncrewed and crewed aerial surveys (https://doi.org/10.5281/zenodo.8089499, Corte et al., 2023c; https://doi.org/10.5281/zenodo.10100968, Corte et al., 2023f; https://doi.org/10.5281/zenodo.10074530, Corte et al., 2023g; https://doi.org/10.5281/zenodo.10101236, Corte et al., 2023h; https://doi.org/10.5281/zenodo.7713146, Corte et al., 2023b). We have determined the bathymetry of the most downstream proglacial lake and the thickness of the sediments deposited on its bottom (https://doi.org/10.5281/zenodo.7682072, Corte et al., 2023a). The water depth at four different locations within the hydrographic network of the proglacial area (https://doi.org/10.5281/zenodo.7697100, Corte et al., 2023d) and the bedload at the glacier snout (https://doi.org/10.5281/zenodo.7708800, Corte et al., 2023e) have also been continuously monitored. The synergy of our approach enables the characterization, monitoring, and understanding of a set of complex and interconnected processes occurring in a proglacial area.

Isotope Hydrograph Separation Reveals Rainfall on the Glaciers Will Enhance Ice Meltwater Discharge to the Himalayan Rivers

AbstractThe Indian Summer Monsoon (ISM) and meltwater from the Himalayan are the two most important sources of water in the Indian subcontinent. However, the impact of ISM on Himalayan glaciers and subsequent stream hydrology remains largely unknown. To provide new insight into the impact of rainfall on glacial hydrology, here we present hydro‐meteorological and time‐series observations of meltwater stable water isotope compositions from the snout of the Chorabari glacier in the Upper Ganga Basin, Central Himalayas across the ablation season corresponding to 2019. We observe that rainfall events (>2 mm d−1) on the glacier enhance discharge driven by ice meltwater in River Mandakini. Energy balance calculations reveal that one of the drivers behind enhanced ice meltwater contribution could be rain‐induced melting of the glacier where rainfall on the ice surface melts the glacier producing up to 13% of the total discharge at the glacier snout. Further, rainfall on glacier surface have other control on glacial processes—for example, snow metamorphism, ice flow dynamics such as short‐term acceleration in ice speed flow, and reorganization of the englacial and subglacial drainage network—that are poorly studied and needs further investigation. We conclude rainfall events on the glacier have a complex control on mountain hydrology. This study, therefore, provides an interpretative framework that calls for additional assessments of the direct and indirect impact of rainfall in glacial hydrology.

Evolutionary model for glacial lake-outburst fans at the ice-sheet front: Development of meltwater outlets and origins of bedforms

Large-scale landforms originated from jökulhlaups or glacial lake-outburst floods (GLOFs), and their small-scale components help in recognising the sedimentary environment of the flood. The GLOF fans that developed along the Pleistocene ice-sheet margin have not been investigated in detail, and north-eastern Poland, with its Megaflood Landform System and Bachanowo and Szeszupka fans, seems ideal for landform and sedimentary studies. This paper provides (1) an important opportunity to recognise the origins of glacier lake-outburst flood outlets and their evolution during two GLOFs and (2) a model of the origin of ice-marginal fans considering changes in sedimentary environment reflecting flood stages. During the first GLOF (GLOF1), the rising stage of meltwater burst triggered the formation of a supraglacial outlet and the development of the Szeszupka outburst fan. During the pulsed peak discharge, subglacial multi-channelised meltwater outburst caused the formation of the Bachanowo Gate, which was finally transformed at the flood waning stage. Such processes were associated with the widening of the floodwater subglacial routeway, when floodwater outlets rapidly spread across the glacier snout. In contrast, GLOF2 was responsible only for the Szeszupka fan erosion and development of outburst terraces. The small-scale bedforms continuum, recognised on the outburst fan surface, is associated with the development of streamlined erosional residuals, scours and their trains during the rising stage and peak discharge, while the waning stage and very end of flood conditions were favourable to the formation of pendant bars, distributive channels with erosional bars and chute bars, regardless of the feeding systems of the outburst fans.The fan deposits were OSL-dated and revealed either, likely, overly old ages or an age of 13.2 ± 0.9 ka. The latter age would imply the ‘normal’ meltwater outflow having a correlation with the events in the region. Nevertheless, this age might be considered a minimum age of the flood.

Ice-rafted dropstones at midlatitudes in the Cretaceous of continental Iberia

Abstract The Cretaceous is widely considered to have been a period subjected to super-greenhouse conditions. Here, we provide multiscale sedimentologic evidence of glaciers developing at mid-paleolatitudes (~45°N) in continental Iberia during the Hauterivian cold snap. Striated and faceted ice-rafted glacial dropstones (cobble to boulder size) and striated and grooved silt- to sand-sized grains (ice-rafted debris [IRD]) occur in a lacustrine sequence of the Enciso Group in the eastern Cameros Basin, Spain. The ice-rafted materials constitute the first evidence reported for a Cretaceous continental cryospheric record in Europe, and they are attributed to calving of glacier snouts, releasing icebergs into an ice-contact lake. The sedimentary succession resembles glacial-deglacial records in lakes overridden by the late Pleistocene Laurentide Ice Sheet in eastern Arctic Canada. The Iberian glacial succession was coeval with plateau permafrost in Asia and IRD records in the Arctic and Australia, revealing a stronger than previously thought cryosphere during the global Hauterivian cold snap.

Glacier–rock glacier interactions in the eastern Hindu Kush, Nuristan, Afghanistan [35.92,71.13] in the period 1976–2019

ABSTRACT Landsystem relationships between glaciers and rock debris supply in a mountain landscape domain, (), are described. Decimal latitude-longitude [dLL] geolocations are used to identify features and transects in an information landscape. Geo-located features are coded, enabling transects between a 1976 expedition and 2019 Google Earth imagery to be compared. Rock debris is progressively added to 1-3 km long glaciers which become debris-covered. Cirque glaciers eventually assume rock glacier (RG) forms when supraglacial debris loads are high. Some rock glacier snouts reach main valley floors and still advance over meadows. This behaviour is attributed to high geomorphic activity producing rock detritus and transport to glaciers in the early Little Ice Age. The advances of rock glacier snouts are a consequence of thinning; low-angle glaciers still moving beneath debris-covered glaciers (GLd) covers. Persistent melt pools continue to develop within the surface debris cover of glaciers and rock glaciers and expose glacier ice. All the rock glaciers are below the regional snowline and permafrost can be discounted for rock glacier formation. Scree slope (SS) development may ultimately be sufficient to cover bare glacier ice moving from a glacier (GL) to debris-covered glacier (GLd) to rock glacier (RG). Reverse slopes in the debris at the foot of screes mark the mass continuum of glacier flow below the debris cover, not the ‘rooting zone’ of a permafrost-derived RG. Scree slopes themselves show no evidence of rock glacier-like flow. A simple glacier ice-debris transport continuum model is sufficient and necessary for rock glacier formation and flow.

Constraining regional glacier reconstructions using past ice thickness of deglaciating areas – a case study in the European Alps

Abstract. In order to assess future glacier evolution and meltwater runoff, accurate knowledge on the volume and the ice thickness distribution of glaciers is crucial. However, in situ observations of glacier thickness are sparse in many regions worldwide due to the difficulty of undertaking field surveys. This lack of in situ measurements can be partially overcome by remote-sensing information. Multi-temporal and contemporaneous data on glacier extent and surface elevation provide past information on ice thickness for retreating glaciers in the newly deglacierized regions. However, these observations are concentrated near the glacier snouts, which is disadvantageous because it is known to introduce biases in ice thickness reconstruction approaches. Here, we show a strategy to overcome this generic limitation of so-called retreat thickness observations by applying an empirical relationship between the ice viscosity at locations with in situ observations and observations from digital elevation model (DEM) differencing at the glacier margins. Various datasets from the European Alps are combined to model the ice thickness distribution of Alpine glaciers for two time steps (1970 and 2003) based on the observed thickness in regions uncovered from ice during the study period. Our results show that the average ice thickness would be substantially underestimated (∼ 40 %) when relying solely on thickness observations from previously glacierized areas. Thus, a transferable topography-based viscosity scaling is developed to correct the modelled ice thickness distribution. It is shown that the presented approach is able to reproduce region-wide glacier volumes, although larger uncertainties remain at a local scale, and thus might represent a powerful tool for application in regions with sparse observations.

Last Glacial Maximum and subsequent glacial chronology in the monsoon-dominated Sikkim Himalaya, India

The study investigates sequential evolution of glacial-landforms in relation to paleo-climate by establishing glacial chronology in Zemu and East-Rathong Glaciers valleys, Sikkim, Eastern Himalaya during the Late-Quaternary. This region is dominated by the Indian summer monsoon, followed by winter rain from the NE-monsoon and Westerlies which influence the glaciers. The study relies on field-based geomorphological mapping and geospatial datasets. The Toe-to-Headwall Altitude Ratio, Toe-to-Summit Altitude Method, and Maximum Elevation of Lateral Moraines methods have been used to calculate the equilibrium line altitudes (ELA) to assess magnitudes of glacial changes over time. OSL dating is used to assess the timing of glacial stages. Additionally, a comparison is made with ELA changes, the distance of moraines from the present glacier snouts, and established glacial chronologies in neighboring areas. The existing landscape depicts the dominant role of the region's present and past glacial processes. The region is also modified by periglacial, paraglacial, and fluvial processes. Four glacial stages have been identified in the region during the late-Quaternary period, contemporaneous to the Last Glacial Maximum, Younger Dryas, Late-Holocene, and Little Ice Age. The first stage (Sikkim-I), marked by dissected trimlines up to ∼16 km downstream, appears to belong to the global Last Glacial Maximum and dated to ∼18.276 ± 0.589 ka with a change of −519.5 m and − 3.4 °C in ELAs and temperature, respectively. The second stage, Sikkim-II is represented by lateral moraines running up to ∼5 km downstream in U-shaped valleys and seems to coincides with the Younger Dryas with ELAs depression of −261.8 m along with a − 1.7 °C drop in temperature. The third Stage (Sikkim-III), marked by small pairs of stable lateral moraines covered with shrubs within ∼3 km downstream, probably belongs to the late Holocene when ELAs and temperature dropped by −177.3 m and − 1.2 °C, respectively. The fourth stage (Sikkim-IV) is notified by a dumped heap of end moraines within ∼2 km downstream, possibly occurred during the LIA with a depression of −72.4 m in ELAs and − 0.5 °C in temperature. These glacial stages are synchronous with the glaciations in the neighboring regions of Thangu in north-Sikkim, Bhutan, and eastern Himalaya syntax. However, the findings of the study differ from the westerly dominated NW Himalayas, broadly.

Active temperate glacial landsystem evolution in association with outwash head/depositional overdeepenings

AbstractThe response of temperate glaciers to rapid climate warming is reflected in the geomorphology (landsystem) resulting from snout recession. This paper develops a locally diverse process‐form model of active temperate glaciers through mapping and quantification of historical landscape change on the Fjallsjökull‐Hrútárjökull foreland, SE Iceland. Quantification of volumetric and areal changes on the foreland are based on time series of archival aerial images for the period 1945–1998, high‐resolution satellite imagery for 2014 and digital elevation models of differences derived from time series of UAV imagery for the years 2014, 2016, 2018, 2019 and 2022. Landscape change and glacier snout behaviour since 1945 highlights the importance of azonal and potentially intrazonal signatures in temperate glacial landsystems, particularly: (1) the development and collapse of partially supraglacial outwash fans to produce outwash heads fronting depositional overdeepenings; and (2) the emergence of ice‐cored eskers that record the evolution of englacial drainage networks operating over overdeepenings. Such landform assemblages are manifested as substantial ice‐cored/hummocky terrains, a characteristic of deglaciating forelands that is likely to be widely replicated wherever ice‐contact glacifluvial assemblages create outwash heads that act as depositional overdeepenings. Due to its significantly greater supraglacial debris cover, complete de‐icing of the Hrútárjökull snout in response to post‐1945 warming was delayed until around 2014. This constitutes a prime example of incremental stagnation, which in a rapidly warming climate has resulted in significant landscape change (land surface elevation collapse of 0.8 m a−1) over the last 8 years.

Spatio-temporal assessment of regional scale evolution and distribution of glacial lakes in Himalaya

Glacial lakes are a potential threat to the livelihoods and precious infrastructures in the Himalayan region. The expansion of these lakes under the influence of global warming further poses a grievous risk of natural disasters in the form of glacial lake outburst flood (GLOF) that necessitates regular monitoring to reduce and mitigate its implications. This research focuses on the regional scale distribution and evolution of glacial lakes in the Himalayan mountain range with their causes. We used Landsat thematic mapper (TM) and operational land imager (OLI) images, Google Earth imageries, Shuttle radar topographic mission (SRTM) Digital Elevation Model, and Aphrodite climatic data to study lake evolution and its controlling parameters. A total of the 5,409 glacial lakes was taken for the size expansion analysis, which excludes supraglacial lakes. An expansion rate of 2.98%/yr and 1.01%/yr in glacial lakes number and size was found from 1990 to 2020, respectively. The glacial lakes are distributed mainly in Langtang, Bhutan, Sikkim and Everest region; while, new lakes are forming at higher elevations continuously. The highest lake size expansion was noted in 2015–2020 (36.51%) followed by 2000–2010 (21.72%) and 2010–2015 (10.65%), while 1990–2000 (3.36%) showed a lowest expansion rate. The highest expansion rate was noticed near an elevation band of 5000–5500 m. Moreover, lakes in the central and eastern Himalaya are highly decrease by climatic change, i.e., increase in temperature a decrease precipitation. The feature selection algorithm was used to identify the importance of various controlling parameters, which showed temperature change rate, glacier fed lake, glacier snout steepness, proximal distance, glacier calving frontal width, precipitation change rate and lake type gave higher weightage towards lake size change.

Temporary Survival Increasing the Diversity of Culturable Heterotrophic Bacteria in the Newly Exposed Moraine at a Glacier Snout.

Laohugou Glacier No. 12 is located on the northern slope of the western Qilian Mountains with a temperate continental wet climate and an extremely cold winter. Bacteria in a newly exposed moraine have to cope with various pressures owing to deglaciation at the glacier snout. However, limited information is available regarding the high diversity and temporary survival of culturable heterotrophic bacteria under various environmental stresses. To examine the tolerance of extremophiles against varying environmental conditions in a newly exposed moraine, we simulated environmental stress in bacterial cultures. The results showed that the isolated strains belonged to actinobacteria, Proteobacteria, Bacteroidetes, Deinococcus-Thermus, and Firmicutes. Actinobacteria was the most abundant phylum, followed by Proteobacteria, at both high and low temperatures. Pseudarthrobacter was the most abundant genus, accounting for 14.2% of the total isolates. Although several microorganisms grew at 10 °C, the proportion of microorganisms that grew at 25 °C was substantially higher. In particular, 50% of all bacterial isolates grew only at a high temperature (HT), whereas 21.4% of the isolates grew at a low temperature (LT), and 38.6% of the isolates grew at both HT and LT. In addition, many radiation-resistant extremophiles were identified, which adapted to both cold and oxidative conditions. The nearest neighbors of approximately >90% of bacteria belonged to a nonglacial environment, such as oil-contaminated soil, rocks, and black sand, instead of glacial niches. This study provides insights into the ecological traits, stress responses, and temporary survival of culturable heterotrophic bacteria in a newly exposed moraine with variable environmental conditions and the relationship of these communities with the non-glacial environment. This study may help to understand the evolution, competition, and selective growth of bacteria in the transition regions between glaciers and retreats in the context of glacier melting and retreat owing to global warming.

Microbial community dynamics from a fast-receding glacier of Western Himalayas highlight the importance of microbes in primary succession, nutrient recycling, and xenobiotics degradation

Climate change has caused an unimaginable upsurge in glacier retreats. The melted ice exposes bare areas offering sites for new ecosystem development where primary microbial succession initiates the build-up of organic mass for plant colonisation. Chhota Shigri glacier is one such glacier that has retreated immensely and provides an ideal site for microbial succession studies. Here, we studied the shift in microbial communities and their functional traits along the glacier forefield from bare glacier snout to mature vegetated foreland through amplicon and whole metagenome sequencing approaches. The forefield sites closer to the glacier snout were abundant in the microbial phyla, such as Patescibacteria, Gemmatimonadota, Proteobacteria, Bacteroidota, Chloroflexi, Cyanobacteria, Verrucomicrobiota and Myxococcota that have potential in carbon (C), nitrogen (N), and sulphur (S) cycling. The sites away from glacier snout were abundant in the phyla Actinobacteria and Acidobacteriota, which are heterotrophic and help in organic carbon recycling. The microbes at the sites closer to the glacier terminus were richer and more diverse than those away from the terminus. The abundance and diversity of the microbes were primarily affected by the local soil's temperature, followed by pH and elements concentration (Calcium (Ca), Phosphorous (P), Potassium (K), Iron (Fe), Copper (Cu), Zinc (Zn), Lead (Pb)). Moreover, the whole-genome metagenome study revealed the prevalence of genes associated with N, C and S cycling. Additionally, the microbes and genes involved in xenobiotics compounds (Aminobenzoate, Benzoate, Caprolactam) degradation are also observed in the forefield soils. This study pointed out microbial successional gradients, the effect of local environmental factors in driving microbial succession and the role of glacier microbes in nutrients cycling and xenobiotics degradation along glacier forefield, helping our understanding of microbial succession and functional roles played by the microbes at nutrient-poor glacial soil.

Geomorphological map of Breiðamerkursandur 2018: the historical evolution of an active temperate glacier foreland

ABSTRACT We present a geomorphological map of Breiðamerkursandur, the outwash plain and foreland of Breiðamerkurjökull, an outlet glacier of the Vatnajökull ice cap, Southeast Iceland. We trace the glacial retreat of the glacier snout since its historical late nineteenth century Little Ice Age (LIA) maximum extentand the concomitant development of the glacial drainage pathways. Since the outlet began retreating from its LIA terminal position, a 120 km2 area of foreland has been exposed. The mapped geomorphology is a supplementary continuation of previous surveys in the 20th century, which highlighted the geomorphology and ice margin for the years 1945, 1965 and 1998. Since the 1998 landsystem map, Breiðamerkurjökull has retreated a further 0.6–4.0 km and 29 km2 has been exposed. This new map was prepared with the use of remote sensing, LiDAR DEM, a range of oblique aerial photographs and satellite images, written documents, in-field survey measurements and refined landform classifications to more accurately trace the position of the retreating snout and its outlet streams over the last 130 years.

Microplastic contamination of supraglacial debris differs among glaciers with different anthropic pressures

Microplastic (MP) contamination is ubiquitous and widespread in terrestrial and aquatic ecosystems, including remote areas. However, information on the presence and distribution of MPs in high-mountain ecosystems, including glaciers, is still limited. The present study aimed at investigating presence, spatial distribution, and patterns of contamination of MPs on three glaciers of the Ortles-Cevedale massif (Central Alps, Northern Italy) with different anthropic pressures, i.e., the Forni, Cedec and Ebenferner-Vedretta Piana glaciers. Samples of supraglacial debris were randomly collected from the glaciers and MPs were isolated. The mean amount (±SE) of MPs measured in debris from Forni, Cedec and Ebenferner-Vedretta Piana glaciers was 0.033 ± 0.007, 0.025 ± 0.009, and 0.265 ± 0.027 MPs g−1 dry weight, respectively. The level and pattern of MP contamination from the Ebenferner-Vedretta Piana glacier were significantly different from those of the other glaciers. No significant spatial gradient in MP distribution along the ablation areas of the glaciers was observed, suggesting that MPs do not accumulate toward the glacier snout. Our results confirmed that local contamination can represent a relevant source of MPs in glacier ecosystems experiencing high anthropic pressure, while long-range transport can be the main source on other glaciers.

Phenylobacterium glaciei sp. nov., isolated from Vestrebroggerbreen, a valley glacier in Svalbard, Arctic.

A Gram-stain-negative, rod-shaped bacterial strain designated as 20VBR1T was isolated from a valley glacier (Vestrebroggerbreen) snout ice sample from Ny-Ålesund, Svalbard, Arctic. The colonies were smooth, circular and light creamish on half-strength R2A agar and grew at 10-35 °C (optimum, 20 °C), at pH 6.5-8.0 (optimum, 7.0) and with 0-2.5 % (w/v) NaCl (optimum, 0.5 %). 16S rRNA gene sequence analysis revealed that strain 20VBR1T belonged to the genus Phenylobacterium and was most closely affiliated to Phenylobacterium aquaticum W2-3-4T (97.65 % similarity), Phenylobacterium haematophilum LMG 11050T (97.57 %) and Phenylobacterium koreense Slu-01T (96.91 %). 20VBR1T has a genome size of 4.24 Mb, comprising 4185 predicted genes with a DNA G+C content of 67.86 mol%. DNA-DNA hybridization experiments indicated that the DNA-DNA relatedness between strain 20VBR1T and P. aquaticum KACC 18306T was 41.95±4.36 %, well below the threshold (<70 %) to delineate bacterial species. Genome relatedness indexes revealed that the average nucleotide identity and digital DNA-DNA hybridization values between 20VBR1T and its closest phylogenomic relative, P. aquaticum KACC 18306T, were 78.97 and 22.10 %, respectively. The predominant isoprenoid quinone was ubiquinone (Q-10) and the major polar lipids were phosphatidylglycerol, one unknown phospholipid, one unknown glycolipid and four unidentified polar lipids. The major fatty acids (>10 %) of strain 20VBR1T were summed feature 8 (comprising C18 : 1 ω7c and/or C18 : 1 ω6c), summed feature 3 (comprising C16 : 1 ω6c and/or C16 : 1 ω7c) and C16 : 0. Based on the physiological, biochemical, chemotaxonomic, phylogenetic and phylogenomic analyses, isolate 20VBR1T is considered to represent a novel species of the genus Phenylobacterium, for which the name Phenylobacterium glaciei sp. nov. is proposed. The type strain is 20VBR1T (=JCM 33227 T=DSM 111428 T=MCC 4220 T).

Assessing the Contribution of Glacier Melt to Discharge in the Tropics: The Case of Study of the Antisana Glacier 12 in Ecuador

Tropical glaciers are excellent indicators of climate variability due to their fast response to temperature and precipitation variations. At same time, they supply freshwater to downstream populations. In this study, a hydro-glaciological model was adapted to analyze the influence of meteorological forcing on melting and discharge variations at Glacier 12 of Antisana volcano (4,735–5,720 m above sea level (a.s.l.), 1.68 km2, 0°29′S; 78°9′W). Energy fluxes and melting were calculated using a distributed surface energy balance model using 20 altitude bands from glacier snout to the summit at 30-min resolution for 684 days between 2011 and 2013. The discharge was computed using linear reservoirs for snow, firn, ice, and moraine zones. Meteorological variables were recorded at 4,750 m.a.s.l. in the ablation area and distributed through the altitudinal range using geometrical corrections, and measured lapse rate. The annual specific mass balance (−0.61 m of water equivalent -m w.e. y−1-) and the ablation gradient (22.76 kg m−2 m−1) agree with the values estimated from direct measurements. Sequential validations allowed the simulated discharge to reproduce hourly and daily discharge variability at the outlet of the catchment. The latter confirmed discharge simulated (0.187 m3 s−1) overestimates the streamflow measured. Hence it did not reflect the net meltwater production due to possible losses through the complex geology of the site. The lack of seasonality in cloud cover and incident short-wave radiation force the reflected short-wave radiation via albedo to drive melting energy from January to June and October to December. Whereas the wind speed was the most influencing variable during the July-September season. Results provide new insights on the behaviour of glaciers in the inner tropics since cloudiness and precipitation occur throughout the year yielding a constant short-wave attenuation and continuous variation of snow layer thickness.

The historical emergence of a geometric and sinuous ridge network at the Hørbyebreen polythermal glacier snout, Svalbard and its use in the interpretation of ancient glacial landforms

The post Little Ice Age recession and downwasting of Hørbyebreen, a Svalbard polythermal glacier, has revealed a sub-polar glacial landsystem within which a geometric and sinuous ridge network (GSRN) has evolved by ice melt-out. Spatio-temporal evolution of these features is evaluated using time series of remote sensing data, aerial photography, DEMs and field observations. The GSRN is interpreted as an assemblage of crevasse and hydrofracture infills branching out from parent eskers, a signature of the rapid release of pressurised subglacial and englacial meltwater, likely related to surge-induced jökulhlaups. This gives rise to a range of component materials including till, gravel and interdigitated till and gravel. Ancient examples of such jökulhlaup-diagnostic GSRN in ice sheet settings are recognised as elongate zones of conjugate, reticulate and honeycomb patterned ridges in close association with eskers that often also display reticulate ridge patterns. We present a conceptual model of a process-form continuum for the production of different styles of GSRN that identifies: a) surge crevassing, indicated by glacier wide GRN and zig-zag eskers; b) ice stream surging plug flow, indicated by linear assemblages of GRN; c) sub-marginal till emplacement in radially crevassed active temperate snouts, indicated by narrow concentric arcs of GRN linked to push moraines; and d) jökulhlaup-induced hydrofracture, indicated by linear assemblages of GSRN.

The explosive basaltic Katla eruptionin 1918, south Iceland, I: Course of events, tephra fall and flood routes

The 23-day long eruption of the ice-covered Katla volcano in 1918 began on October 12 and was over by November 4. Seismicity preceding and accompanying the onset had already started by 11:30 on October 12, while the eruption broke through the glacier around 3 PM. The plume rose to 14–15 km on the first day. The eruption caused widespread tephra fall, accompanied by lightning and thunder. Tephra fall from the intense first phase (October 12–14) was reported from Höfn, 200 km east of Katla, Reykjavík, 150 km to the west and Akureyri, 240 km to the north. The initial phase was followed by more sporadic activity for a week, and a second intense phase (October 22–24), with heavy tephra fall in populated areas east and south of the volcano. Skaftártunga (25–35 km east of Katla), was the worst hit farming district, with reported tephra thickness of 6.5–10 cm in total, collecting into drifts tens of cm thick. The Vík village suffered almost continuous tephra fall for 13 hours on October 24 and 25, leaving a 2 to 4 cm thick tephra layer on the ground. Tephra reached Reykjavík four times but minor tephra fallout («1 mm) occurred. Tephra also reached northern, western and eastern Iceland. In addition to producing the 0.9–1.0 km3 tephra layer, which may as freshly fallen have been 1.1–1.2 km³, the eruption was accompanied by a jökulhlaup that flooded the Mýrdalssandur plain and neighbouring areas. The jökulhlaup on October 12 had two separate phases. The first phase is considered to have flowed supraglacially down the lower parts of the Kötlujökull outlet glacier into the Leirá, Hólmsá and Skálm rivers (northern fork), and the Sandvatn and Múlakvísl rivers (southern fork). It was much more widespread than the second phase which emerged from below the glacier snout and was confined to the western part of Mýrdalssandur. That phase carried huge icebergs and massive sediment load onto the sandur plain.

Glacial processes and landforms

AbstractFrom 1965 to 2000 glacial geomorphology became increasingly specialized and developed significantly due to technological improvements, particularly in remote sensing, surveying and field-based glaciological process studies. The better understanding of basal thermal regimes in ice sheets and glaciers led to the development of concepts such as spatial and temporal migration of ice divides in dynamic ice sheets that could overprint subglacial landform assemblages, debris entrainment processes related to polythermal glacier systems, and glacier and ice sheet beds composed of cold and warm based mosaics. Process observations at the ice–bed interface led to the discovery of the third glacier flow mechanism, substrate deformation, which provided the impetus to reconstruct the genesis of subglacial bedforms such as drumlins and to evaluate the origins and potential flow law for till. Numerical evaluations of glacial erosion led to a better understanding of abrasion and quarrying as well as the erection of genetic models and erosion rates for larger-scale features such as U-shaped valleys and cirques. Linkages were made between debris transport pathways and moraine construction in supraglacial environments, with the role of glacier structure being linked to specific landforms, such as medial, lateral, hummocky and ice-cored moraines as well as rock glaciers. Our appreciation of the erosional and depositional impacts of glacifluvial systems was enhanced significantly with the advent of process observations on the hydrology of modern glaciers as well as the final vindication of J.H. Bretz and his proposed jökulhlaup origins of the Channelled Scablands and the Missoula Floods. In addition to the increasing numbers of studies at modern glacier snouts, the embracing of sedimentology by glacial geomorphologists was to result in significant developments in understanding the process-form regimes of subglacial, marginal and proglacial landforms, particularly the recognition of landform continua and hybrids. Advances resulting from this included the recognition of different modes of moraine and glacitectonic thrust mass development, lithofacies models of the varied glacifluvial depositional environments, and the initial expansion of work on the sediments and depocentres of glacimarine settings, the latter being the result of glacial research taking to submersibles and ice-strengthened ships for the first time. A similarly new frontier was the expansion of research on the increasingly higher resolution images returning from Mars, where extraterrestrial glaciations were recognized based on comparisons with Earth analogues. Holistic appreciations of glaciation signatures using landform assemblages were developed, initially as process-form models and later as glacial landsystems, providing an ever-expanding set of templates for reconstructing palaeoglaciology in the wide variety of topographic and environmental settings, which also acknowledge spatial and temporal change in glacier and ice sheet systems.

Subglacial Channels, Climate Warming, and Increasing Frequency of Alpine Glacier Snout Collapse

AbstractAlpine glacier retreat has increased markedly since the late 1980s and is commonly linked to the effects of rising temperature on the surface melt. Less considered are processes associated with glacier snout‐marginal surface collapse. A survey of 22 retreating Swiss glaciers suggests that collapse events have increased in frequency since the early 2000s, driven by ice thinning and reductions in glacier‐longitudinal ice flux. Detailed measurement of a collapse event at one glacier showed 0.02 m/day vertical surface deformation above a meandering main subglacial channel. However, with low rates of longitudinal flux (&lt;1.3 m/year), this was insufficient to close the channel in the snout marginal zone. We hypothesize that an open channel maintains contact between subglacial ice and the atmosphere, allowing greater incursion of warm air up‐glacier, thus enhancing melt from below. The associated meandering of subglacial channels at glacier snouts leads to surface collapse and removal of ice via fluvial processes.

Synergistic analysis of satellite, unmanned aerial vehicle, terrestrial laser scanner data and process-based modelling for understanding the dynamics and morphological changes around the snout of Gangotri Glacier, India

The glaciated areas of the Himalaya often experience mass movement, glacial lake outburst flood and other associated hazards, posing threat to the communities and infrastructure in the downstream areas. A large debris flow occurred during July 16–19, 2017 near the present snout of the Gangotri Glacier in the Garhwal Himalaya, India resulting in significant geomorphological changes in the vicinity. The present study assesses the applicability of multi-source remote sensing data from satellites, unmanned aerial vehicle (UAV) and terrestrial laser scanner (TLS) along with process-based modelling to understand and quantify glacier snout dynamics and morphological changes around Gangotri Glacier in the Garhwal Himalaya of India. We show that retreat rates of Gangotri Glacier snout along the lateral flowlines are (left flowline 29.6 m year−1; right flowline 60.5 m year−1) are significantly higher compared to the central flowline (18.2 m year−1) during 2010–2020 leading to total loss in glacial ice area of 0.11 ± 0.015 km2. The snout dynamics and evolution of the new channel from the terminus of the adjoining Meru Glacier, connecting the moraine-dammed glacial lake and the Bhagirathi River, suggest that retreat of the Gangotri Glacier, intense precipitation and excessive seepage from the glacial lake were the important drivers of the debris flow in July 2017. The accumulated debris occupied an area of ~0.25 km2 near the snout of the Gangotri Glacier and shifted Bhagirathi River by 36–200 ± 9.35 m towards northeast. The synergistic analysis of pre- and post-event satellite, UAV and TLS-based digital elevation models (DEMs) and satellite images indicate that about −8 ± 0.066 × 106 m3 of sediments were generated by the debris flow. The results from remote sensing data suggest that a significant portion (~60%) of the deposited debris has been transported to the downstream areas between July 16–19, 2017 and October 2, 2017. Regular monitoring of the area is recommended, especially in light of climate change using earth observation data and ground measurements. The multi-source integrated framework implemented in this study is generic and can be applied for any debris flow or landslide studies in glaciated terrain.