Proglacial Environments Research Articles

Supraglacial and subglacial ecosystems contribute differently towards proglacial ecosystem communities in Kuoqionggangri Glacier, Tibetan Plateau

Glaciers are experiencing unprecedented global warming, resulting in significant changes to microbial communities and nutrient transport within glacial ecosystems. However, the influence of supraglacial and subglacial ecosystems on the proglacial ecosystem remains poorly understood. Here, we investigated microbial communities across seven habitats in three glacial ecosystems on the Tibetan Plateau using 16S rRNA sequencing. Our results revealed that the proglacial ecosystem exhibited higher alpha diversity but lower network stability than other ecosystems. Moreover, supraglacial and subglacial ecosystems contributed differently to the community diversity and stability of the proglacial ecosystem. Supraglacial ecosystems provided more high-abundance species and had a greater impact on the proglacial ecosystem’s stability, while subglacial ecosystems released a broader range of diverse taxa. These findings highlight the distinct influences of supraglacial and subglacial ecosystems on microbial community dynamics in proglacial environments, offering insights into their interactions and potential impacts on downstream environments as glaciers retreat.

Retreat of the Greenland Ice Sheet leads to divergent patterns of reconfiguration at its freshwater and tidewater margins

Abstract Greenland's marine- and land-terminating glaciers are retreating inland due to climate warming, reconfiguring the way the ice sheet interacts with its proglacial environment. Here we use three decades of satellite imagery to determine whether the ice-sheet margin is becoming more or less exposed to marine and lacustrine processes. During our 1990–2019 study period, we find that the length of ice-sheet perimeter in contact with the ocean shrank by 12.3 ± 3.8% (196.2 ± 10.4 km), due to the retreat of marine-terminating glaciers into narrower fjords. On the other hand, we find that the length of the ice-sheet perimeter in contact with freshwater lakes exhibited more divergent trends that is better explored at regional scales. The length of ice–lake boundaries increased in southwest, north and northwest Greenland but declined in southeast and central east Greenland. The magnitude of change we document during our study period leads us to conclude that the ice sheet is poised for further, substantial reconfiguration in the coming decades with consequences for the flux of fresh water, nutrients and primary productivity in Greenland's terrestrial and oceanic environment.

Physical and chemical characterization of remote coastal aquifers and submarine groundwater discharge from a glacierized watershed

AbstractCoastal aquifers play an important role in marine ecosystems by providing high fluxes of nutrients and solutes via submarine groundwater discharge pathways. The physical and chemical characterization of these dynamic systems is foundational to understanding the extent and magnitude of hydrogeologic processes and their subsequent contributions to the marine environment. We describe a km‐scale experimental field site located in a glaciofluvial delta entering Kachemak Bay, Alaska. Our characterization applies geophysical (ERT and HVSR), hydrogeologic (grain size analyses, slug tests and tidal response analyses) and geochemical (major ions and stable water isotopes) methods to describe the complexity of coastal aquifers in proglacial environments currently experiencing rapid transformations. The hydrogeologic and geophysical techniques revealed thick (20–84 m) sediments dominated by sands and gravels and delineated zones of freshwater, brackish water and saltwater at both high and low tides within the subterranean estuary. Estimates of hydraulic conductivities via multiple approaches ranged from 2 to 250 m d−1, with means across the four methods within the same order of magnitude. Tidal response analyses highlighted a coastal aquifer in strong connection with the sea as evidenced by clear spring‐ and neap‐tidal signals within a proximal piezometric hydrograph. Geochemical sampling revealed coastal groundwaters as substantially enriched in solutes compared to proximal river samples with limited variability across seasons. A clear connection between the Wosnesenski River and the adjacent aquifer was also observed, with concentrated recharge from the river corridor during the meltwater season. This combination of approaches provides the basis for a conceptual model for coastal aquifer systems within the Gulf of Alaska and an upscaled mean daily yield of freshwater and solutes from the delta subsurface. Our findings are critical for subsequent numerical simulations of groundwater flow, tidal pumping and chemical reactions and transport in these understudied environments. This approach may be applied for low‐cost, large‐scale hydrogeologic investigations in coastal areas and may be particularly useful for remote sites where access and mobility are challenging.

A glaciotectonic landform in the Shyok valley, Trans-Himalayan Karakoram Range, India

Abstract This study reports and discusses the first case of glaciotectonic landforms in the Shyok valley of the Trans-Himalayan Karakoram Range, Ladakh, where a large decomposed granite megablock (8.2 km2) along with underlying diamicton is thrust over the unconsolidated Quaternary glaciofluvial sediments along a fault gouge zone near the village of Khalsar. The absence of deformation signatures below the fault gouge indicates that the brittle fault acted as a décollement surface under frozen conditions along which the glaciotectonic megablock was translated. The other deformation features include slickensides, ductile shear, thrust propagation fold noses, clastic dykes and rafts of granite and slate within the diamicton sediments. These features indicate a subglacial glaciotectonic nappe origin of the landform. The presence of juxtaposed brittle to ductile deformation fabric, clastic dykes and the superimposition of deformed decomposed granite and diamicton over the undisturbed fluvial sediments indicates a permafrost glacial margin and proglacial environment under sufficient subglacial hydrodynamic conditions for the entrapment and transportation of the glaciotectonic megablock. The deformation fabric consistently shows a southeast orientation, indicating an advancing glacier motion from northwest to southeast. The Siachen Glacier which formerly flowed down the Nubra valley is the most likely cause of the Khalsar glaciotectonic landform.

Unraveling the sources of major, trace and rare earth elements in the waters of a high latitude proglacial environment: Weathering vs. atmospheric signature in Northern Patagonia

Glaciers are important water reservoirs and are extremely sensitive to the effects of climate change. The Manso River basin, in Northwest Patagonia, Argentina, is a typical hydrological system with actively retreating glaciers. In this article, the proglacial environment was examined to assess the sources and the geochemical processes responsible for the chemical signatures of the following water subsystems: 1) clean glacial meltwaters (supraglacial influence, fed by “clean ice” glaciers); 2) dirty glacial meltwaters (subglacial influence, fed by “dirty ice” debris-covered glacier); and 3) proglacial runoff (river). Results indicated that clean glacial meltwaters present high dissolved immobile and nonmobile trace elements, derived from atmospheric input with an anthropogenic component in Pb, Cu, V, and Ni. Dissolved concentrations of Sr, Mn, Rb, and major ions are the result of carbonation and hydrolysis processes. The dirty glacial meltwater presents the highest dissolved load due to the highest water-rock interaction. The proglacial runoff presents intermediate physicochemical characteristics. At the site where the clean and dirty glacial meltwaters mix, the cation denudation rate is 2075 meq+ m−2 y−1. Downstream, geochemical inverse modeling indicates that the Manso Superior River system produces, by weathering reactions, a rate of dissolved load of 2.67 108 mol year−1, along with a CO2 sequestration of 2.05 108 mol year−1, denoting that proglacial environments are an important scenario in the CO2 cycle. The results of this work provide a baseline for future studies in proglacial environments and highlight the importance of assessing metal concentrations and mobilization within the Andean cryosphere.

Isotopic Constraints on Sources and Transformations of Nitrate in the Mount Everest Proglacial Water.

Glacier melting exports a large amount of nitrate to downstream aquatic ecosystems. Glacial lakes and glacier-fed rivers in proglacial environments serve as primary recipients and distributors of glacier-derived nitrate (NO3-), yet little is known regarding the sources and cycling of nitrate in these water bodies. To address this knowledge gap, we conducted a comprehensive analysis of nitrate isotopes (δ15NNO3, δ18ONO3, and Δ17ONO3) in waters from the glacial lake and river of the Rongbuk Glacier-fed Basin (RGB) in the mountain Everest region. The concentrations of NO3- were low (0.43 ± 0.10 mg/L), similar to or even lower than those observed in glacial lakes and glacier-fed rivers in other high mountain regions, suggesting minimal anthropogenic influence. The NO3- concentration decreases upon entering the glacial lake due to sedimentation, and it increases gradually from upstream to downstream in the river as a soil source is introduced. The analysis of Δ17ONO3 revealed a substantial contribution of unprocessed atmospheric nitrate, ranging from 34.29 to 56.43%. Denitrification and nitrification processes were found to be insignificant in the proglacial water of RGB. Our study highlights the critical role of glacial lakes in capturing and redistributing glacier-derived NO3- and emphasizes the need for further investigations on NO3- transformation in the fast-changing proglacial environment over the Tibetan Plateau and other high mountain regions.

Lithofacies and sequence stratigraphic analysis of the glaciomarine lower Wynyard Formation (Pennsylvanian–early Permian, Tasmanian Basin)

Glaciation during the Late Paleozoic Ice Age climatic interval (~370–260 Ma) was likely dynamic; consisting of numerous ice centers that grew and shrank asynchronously through time. Improvements in understanding of the spatial and temporal depositional complexity of glaciomarine sedimentary systems have shown that in order to characterize the conditions of Late Paleozoic glaciation, glaciogenic depositional systems and their stratigraphy must fundamentally be understood at the local level. To that end, this study reexamines the physical sedimentology and sequence stratigraphy of the type-section of the Permo-Carboniferous, glaciomarine Wynyard Formation (Wynyard Tillite) of the Tasmanian Basin by describing a 415 m thick interval of the formation, beginning at its basal erosional unconformity with the Proterozoic Burnie (Oonah) Formation.The glaciogenic nature of the Wynyard Formation stratigraphy is indicated by the characteristics of clasts throughout the succession (striated, faceted, angular, and variable lithologies and grain sizes). Three glacial depositional environments were interpreted: a grounding zone wedge deposited in an ice-contact setting, glacier-proximal portion of a grounding line fan and/or morainal bank, and cyclopelites deposited in a glacier-intermediate to glacier-distal setting. Mass transport and turbidite deposits are common throughout all facies associations, as is soft sediment deformation likely caused by slumping. Several boulder pavements occur throughout the succession, indicating periodic glacier grounding. Together, these facies associations indicate that this Wynyard Fm succession is composed of glaciogenic sediments that were deposited in sub-aqueous, marine, predominantly proglacial environments. The sequence stratigraphic analysis indicates that this entire succession of the Wynyard Fm was likely deposited during the single retreat phase of the “Wynyard Glacier”, with one notable readvance over the area.The interpretations made by this work enhance the understanding of glaciation of the Tasmanian Basin during the LPIA through facies analyses and a sequence stratigraphic approach, which allowed for detailed subdivision of lithologies that enabled inferences regarding the type, timing, and extent of the “Wynyard glacier”. This Wynyard Fm succession was likely deposited during a single glacier retreat with some minor readvances that may have occurred on the order of decades to years. Additionally, the glacier's grounding line was likely never more than a few kilometers upglacier (south) of this location during deposition.These findings are significant, because the massive diamictites that comprise this succession had previously been considered homogenous and therefore resisted detailed interpretations. Constraining the often-complex depositional histories of glaciogenic strata in similar fashions across the Tasmanian Basin allows us to better understand how these glaciogenic deposits fit into the global climate system of the Late Paleozoic Ice Age.

Robust estimations of areal grain size distribution from geometric surface roughness in a proglacial outwash area

Rapid glacier mass loss in high-alpine catchments exposes unconsolidated sediments to erosion by meltwater-fed mountain streams, with impact on the catchment-scale sediment dynamics. Proglacial outwash areas (OWA) are a key spatial element in this sediment flux cascade, with grain size distributions (GSD) as an integral variable in current and future glacio-fluvial processes and associated effects.In this study, surface grain size estimation methods based on linear correlations between geometric surface roughness and GSD data are adapted to test this new mapping approach for areal GSD patterns and their changes in a proglacial OWA. Surface roughness is computed with adaptive kernel sizes from high-resolution topographic point clouds derived from UAV-based photogrammetry. For model calibration, ground truth data is manually obtained from 30 dry-exposed GSD sampling patches of 1 m2 each. The novelty and potential of this surface roughness regression model lies in its capability to robustly map GSD percentiles at 1-m cell resolution in highly dynamic proglacial environments and inherent data scarcity, drastically reducing the portion of labour-intensive and time-consuming manual surveying.Our optimized linear regression function for the key figure D84, which is widely used in practice, returns a coefficient of determination of 76.4 %. The linear relation found between the D84 of field GSD and the 84th distribution percentile of surface roughness metrics has a slope of α = 6.01, which is consistent with the range of recently published studies using LiDAR-based and photogrammetric surveys. The presented surface roughness regression model provides realistic surficial estimations of areal GSD patterns in a proglacial domain of sediment remobilization. In addition, this work analyses and discusses detected changes in the estimated D84 over a three-month period. A systematic shift is identified for sediment compositions with an initial D84 above 60 mm. This is thought to be an effect of the original image quality and variable lighting conditions between photogrammetric surveys and indicates that best practice should include careful survey planning for most uniform flight settings. Nevertheless, visually verified significant changes in D84 along frequently wet low-flow channels can be detected automatically, and thus the findings demonstrate the feasibility of this GSD monitoring approach for tracking fluvial re-working of surface sediment.

Carboniferous marine deposits of the Tontal section suggest that no Protoprecordillera existed along the Western Gondwana margin

We present new palaeontological and stratigraphic data from a poorly known section located in the Tontal Range, Argentina, whose importance is key to defining the character of a hypothetical Carboniferous mountain chain, the Protoprecordillera. The Tontal Range composed the core of the hypothetical Protoprecordillera, also called the Tontal arch. The section described here comprises Mississippian and Pennsylvanian marine and mixed marine–terrestrial units that were deposited within a proglacial (non-fjord) environment. A new correlating scheme of Tontal section units is brought based on new biostratigraphic data plus the recent development of a stratigraphic order of Carboniferous units cropping out only 15 km away. The lowermost unit in the Tontal section is Del Ratón Formation conglomerate, which passes upwards into glaciomarine shales correlated with the El Planchón Formation that bears marine bivalves and palynomorphs suggesting a Serpukhovian (Upper Mississippian) age. El Planchón is overlain by the barren Churupatí Formation, with lower units of shallow marine, fan-deltaic conglomerate, passing to fluvial redbeds. The overlying Del Salto Formation has intense intraformational folding due to slumping at its base, and consists of sandstone, organic-rich shale, and shelf carbonate, the latter containing marine invertebrates and palynomorphs that suggest a Bashkirian (Lower Pennsylvanian) age. The Tontal section represents a marginal position within a previously defined strike-slip basin (Milana and Di Pasquo, 2019) that was active during most of the Carboniferous. It was deposited in a shallow marine shelf beside a hummocky coastal landscape, the erosion of which provided rounded gravels deposited in Gilbert-type deltas with associated slumps. We found no indication this area hosted any kind of glaciers, and most of the time it was below sea level. These observations, along with the lack of any mountain-side complex or any alpine-valley glacio-related depositional features remain at this, or any neighbouring sections; suggest that there was no Protoprecordillera mountain chain. Correlation with nearby sections also suggests this margin was not influenced by any prominent topographic highs during the depositional time of the Tontal section (upper Mississipian to Pennsylvanian), but rather that this area was located near sea level, potentially with emergent and positive areas along both margins of the strike-slip basin that allowed preservation of the oldest Carboniferous units of this region. On the other hand, the tendency for generalised subsidence during the Upper Carboniferous over most of the Precordillera, may respond to the development of a volcanic arc westwards over the present Cordillera, associated with the activation of a subduction zone in the present-day Chile, turning most of the area into retroarc basins.

Upper-flow regime bedforms in a subglacial triangular-shaped landform (murtoo), Late Pleistocene, SW Finland: Implications for flow dynamics and sediment transport in (semi-)distributed subglacial meltwater drainage systems

We know less about subglacial meltwater flow properties in distributed inefficient and semi-efficient systems in comparison to those of ice marginal eskers and proglacial environments. While previous studies have indicated the overall common presence of upper-flow-regime (UFR) bedforms in glacigenic settings, facies expressions of subglacial meltwater flows remain poorly documented. Three ca. 3 m deep and up to 70 m long trenches excavated across a triangle-shaped subglacial landform called a murtoo in a Lateglacial to Holocene meltwater route in SW Finland provide a detailed window into sedimentary structures presumably formed ca. 40–50 km away from the coeval subaqueous margin of the Fennoscandian Ice Sheet (FIS). The aim of this paper is to document small-scale bedforms, which formed subglacially by meltwater flow and to characterize the proximal and central parts of the studied murtoo during its early evolutionary phase. We defined seven main facies types that characterize the depositional processes of the unit. Overall, the studied deposits reflect increasing meltwater delivery through time and are characterized by abrupt lateral changes in sedimentary structures and grain size. While the initial deposits are dominated by massive and horizontally laminated silt with sand lenses interpreted as lower-flow-regime deposits, the latter sediments are characterized by sinusoidal stratification, sigmoidal cross-stratification and scours with backsets or chaotic fill interpreted as deposits of antidunes, humpback dunes, chutes-and-pools and cyclic steps of the upper-flow regime. The upper-flow-regime bedforms developed on a 1 m high and 15 m long bed slope and are associated with the formation of a short-lived enlarged water-filled cavity or pond, where supercritical density flows allowed for the deposition of upper-flow regime bedforms. The final coarse-grained murtoo head-bar development, characterized by planar-cross stratified gravel and pebbly sand, indicates avalanche processes that were controlled by grain size.Our results confirm that the core of the murtoo is depositional and meltwater processes played a key role in its deposition. Despite the subglacial setting with a subaqueous ice-sheet margin, the meltwater flow was not permanently characterized by pipe-flow conditions. Overall, the findings contribute to the understanding of semi-distributed subglacial meltwater systems during the retreat of a continental ice sheet (FIS) in a rapidly warming climate.

Determination of plutonium in cryoconite on glacier surfaces in the northeast Tibetan Plateau: Implications for source identification and accumulation

Plutonium isotopes have drawn public attention because of their high radiotoxicity and risk for internal radiation. Cryoconite, dark sediments on the surface of glaciers, is rich in anthropogenic radionuclides. Therefore, glaciers are regarded as not only a temporary sink for radioactive pollutants in the past decades, but also a secondary source during their melting. However, study on activity concentration and source of Pu isotopes in cryoconite materials in Chinese glaciers have not been studies thus far. The present study determined the 239+240Pu activity concentration and 240Pu/239Pu atom ratio in cryoconite and other environmental samples collected in August-one ice cap, northeast Tibetan Plateau. The results showed that the 239+240Pu activity concentration in cryoconite is 2–3 orders of magnitude higher than the background value, suggesting the exceptional capacity of cryoconite to accumulate Pu isotopes. The high 239+240Pu level in cryoconite in the study area was significantly correlated with organic matter and slope, indicating their dominant influence. The average values of the 240Pu/239Pu atom ratio for proglacial sediments (0.175) and grassland soils (0.180) suggested that the global fallout is the dominant source of Pu isotopes pollution. In contrast, the measured 240Pu/239Pu atom ratios in the cryoconite were distinctly lower at 0.064–0.199, with an average of 0.157, indicating that the close-in fallout Pu isotopes from Chinese nuclear test sites is another source. In addition, although the relatively lower activity concentrations of 239+240Pu in proglacial sediments implies that most Pu isotopes are retained in this glacier instead of being redistributed along with cryoconite by meltwater, the potential health and ecotoxicological risks to the proglacial environment and downstream areas cannot be ignored. These results are important for understanding the fate of Pu isotopes in the cryosphere and can be applied as baseline data for radioactivity evaluation in the future.

Glacial Water: A Dynamic Microbial Medium.

Microbial communities and nutrient dynamics in glaciers and ice sheets continuously change as the hydrological conditions within and on the ice change. Glaciers and ice sheets can be considered bioreactors as microbiomes transform nutrients that enter these icy systems and alter the meltwater chemistry. Global warming is increasing meltwater discharge, affecting nutrient and cell export, and altering proglacial systems. In this review, we integrate the current understanding of glacial hydrology, microbial activity, and nutrient and carbon dynamics to highlight their interdependence and variability on daily and seasonal time scales, as well as their impact on proglacial environments.

The Development of Limestone Weathering Rind in a Proglacial Environment of the Hallstätter Glacier

The contemporary retreat of glaciers results in the development of glacial forelands which constitute excellent areas for studies on the initial stages of weathering. This research concentrates on weathering rinds developed on glacially abraded Dachstein limestone surfaces (Eastern Alps) liberated from glacial ice since LIA (mid-19th century). We performed measurements of rock surface micro-roughness and strength (Schmidt hammer), spectral reflectance, and petrographic and microbiological analyses in SEM. There was a time-dependent increase in micro-roughness, decrease in rock strength and decrease in spectral reflectivity, but only within visual light. Rock surfaces on older sites reflected infrared radiation significantly better than younger ones. SEM analysis revealed that angular micro-structures inherited from glacial abrasion dominated in younger sites, eventually giving way to more rounded micro-structures. The structure of rock (micrite versus spar, phlogopite veinlets, etc.) plays a significant role. On older sites, microorganisms were detected within the studied weathering rinds, which probably results in better infrared reflectivity. We advocate the potential role of microorganisms (mainly heterotrophic) in the dissolution of limestone, and the role of cyanobacteria in the formation of the secondary porous limestone layer (extracellular biomineralization).

Understanding the Susceptibility of the Tropical Proglacial Environment in Peru Using Optical Imagery and Radon Measurements

The tropical glaciers of the Cordillera Blanca have played host to some of the most significant mass movements ever recorded in the world and Peru; many proglacial lakes formed in this mountain range have natural dikes made of moraine material, which, if they collapse, would present a risk for the cities located downstream of a proglacial lake, where the proglacial lake Palcacocha has a remarkable background regarding floods. The Sentinel-2 MSI (Multi-Spectral Instrument, Level-2A) has a specific band for snow probability mapping that indicates glaciers and snow cover; this is effective for recognizing proglacial lakes by calculating the NDWIice. It is also helpful for lithology with SWIR for granite moraine deposits and slate moraines in the proglacial environment Palcacocha; these deposits surround the proglacial lake, with NDWIice determining the perimeter where sediment interacts with the rocks and meltwater. In addition, there are high radon concentrations made by ice avalanche impacts on the proglacial lake. Unstable glacier blocks cause ice avalanches into this proglacial lake, and the radon responds to flow variations from these high-impact avalanches. We used the device RadonEye PLus2, which allows real-time detection of radon flux changes in the proglacial environment. Our results indicated that ice avalanches making a high impact in the proglacial lake cause turbulent flow and generate radon concentration marks with a rising magnitude, while the absence of ice avalanches in the lake will cause the values to go down. The relationships of radon concentrations in the atmosphere for a tropical proglacial environment are radon and temperature (R2 = 0.364), radon and humidity (R2 = 0.469). In a passive proglacial environment with prolonged rainfall, radon concentrations tend to decrease, with an inversely proportional relationship between humidity and radon in the tropical proglacial environment. Proglacial lakes in the tropical zone often have large volumes of freshwater with high slopes from tropical glaciers, and climate change effects are an imminent danger for nearby cities.

Where does a glacier end? Integrated geophysical, geomorphological and photogrammetric measurements to image geometry and ice facies distribution

In this study we integrated different techniques, spanning from Ground Penetrating Radar to geomorphological and photogrammetric data, to characterize the glacial and proglacial environments of the Sforzellina Glacier (Central Alps, Italy). Direct data highlighted the presence of debris-covered ice and even of dead ice patches in front of the actual glacier terminus. Such an information was further proved by geophysical data. We try to correlate the dead ice patches occurrence with several parameters such as debris cover thickness, ground temperature, solar radiation, elevation, velocity of glacier retreat, and dip of the topographic surface without finding relevant correlations, except for the local bedrock morphology. In fact, the latter factor seems to be crucial to make the favourable conditions to dead ice patches formation and preservation with time.Since ice is not always outcropping, while dead ice patches never outcrop because they are hidden by continuous debris cover, classical glaciological monitoring techniques are not always successfully applicable.On the basis of the obtained results, we argue that estimates of glacier extension just related to surficial information, like in the case of exclusive use of remote sensing data and outcropping ice monitoring, can produce relevant underestimations. The presence of hidden ice patches, even not strictly part of the glacier body, is further important to quantify the total water equivalent, as well as to make affordable forecasts of the future glaciers evolution.

Glacier fluctuations and a proglacial evolution in King George Bay (King George Island), Antarctica, since 1980 decade.

This study aims to investigate the glacier shrinkage and recent proglacial environment in King George Bay, Antarctica, since 1988 in response to climate change. Remote sensing data (SPOT, Sentinel, Landsat and Planet Scope images) were applied to glacial landforms and ice-marginal fluctuations mapping. Annual mean near-surface air temperature reanalysis solutions from ERA-Interim were analyzed. Moraines and glaciofluvial landforms were identified. The Ana Northern Glacier has the highest retreat value (3.64 km) (and area loss of 31%) in response to higher depth in frontal ice-margin and reveal ocean-glacier linkages. The Ana South Glacier changed from a tidewater glacier to land-terminating after 1995, and had an outline minimum elevation variation of 89 meters, a shrinkage of 0.63 km, and a new proglacial subaerial sector. The Ana South Glacier foreland had recessional moraines (probably formed between 1995 and 2022), lagoons, and lakes. There are many flutings in low-relief environments. The 1980-1989, 1990-1999, 2000-2009, 2010-2019 anomaly plots concerning to the 1980-2019 average for atmospheric temperature, are shown to be a driver of the local glacial trends.

Anthropogenic contaminants in glacial environments II: Release and downstream consequences

Anthropogenic contamination has been detected in glacial and proglacial environments around the globe. Through mechanisms of secondary release, these contaminants are finding their way into glacial hydrological systems and downstream environments, with potential to impact hundreds of millions of people who rely on glacial meltwater for water, food and energy security worldwide. The first part of our progress report outlined the sources and accumulation mechanisms of contaminants in glacial environments (Part I: Inputs and accumulation). Here we assess processes of contaminant release, pathways to downstream environments, and socio-environmental consequences. We reflect on the potential impacts these contaminants could have for human, ecosystem, and environmental health, as well as framing glacial contaminants within the context of the water-food-energy nexus. Improved understanding of these processes and impacts, while crucially embedding local knowledge, will help to develop key policy and mitigation strategies to address future risk of contaminant release from glaciers.

Submarine Geomorphology and Glacimarine Sedimentary Processes Associated to Deglaciation in Europa Fjord, Chilean Patagonia

In a period of high rates of glacier retreat, increasing meltwater discharge from tidewater glaciers can influence marine fjord ecosystems due to increase sediment delivery and accumulation rates in the proglacial environment. Glacier variations and associated changes in glacimarine processes are recorded in the sedimentary record and submarine geomorphology of fjords. In October-November 2017, CIMAR23 Cruise surveyed several fjords adjacent to the Southern Patagonian Icefield (SPI). In this study, we show detailed results of the multibeam bathymetry, backscatter and sub-bottom seismic profiles, and sediment core samples from Europa Fjord, located west of the central SPI area, to improve the analysis of the fjord glacial and sedimentary evolution and to connect its behavior with the other fjords in the region. For the cores 210Pb chronology, magnetic susceptibility, organic carbon, total nitrogen, and stable isotopes (δ13Corg, δ15N) were performed. The seafloor geomorphology showed that the most prominent submarine landforms are transverse morainal ridges, which indicate past stillstand glacier positions; these features formed during the deglaciation of the fjord (latest Pleistocene), and some, perhaps more recently during short episodic advance/retreat events. In the central and mouth fjord areas, erosional features such as lineations are found on the rocky bottom and interpreted as formed by past grounded glaciers. Several submarine moraines are generally well preserved, but some parts are crumbled by slope failures and erosion. Most of the seismic sections are interpreted as the expected subglacial-ice proximal-ice distal succession of facies, characteristic of single retreat environments. The sedimentary record includes bioturbed muds with muddy laminations and variable amounts of coarse sediments interpreted as ice rafted debris, suggesting a proglacial environment, punctuated by calving. From the beginning of the twentieth century there is a tendency to an increase in the terrigenous organic material content, including an abrupt increase during the 80–90s, and a decline in the last decade. This behavior is indicating possibly a general increase of surface terrestrial runoff and, for the last decade, an increase of glacial meltwater input which would be caused by an accelerated deglaciation.

An Assessment of Geophysical Survey Techniques for Characterising the Subsurface Around Glacier Margins, and Recommendations for Future Applications

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.

Ground‐penetrating radar (GPR) investigations of a large‐scale buried ice‐marginal landsystem, Skeiðarársandur, SE Iceland

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‐km2 study area) and deep (reflections recorded at depths up to 100 m) low‐frequency (40 and 100 MHz) ground‐penetrating radar (GPR) survey of the Sandgígur 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 Sandgígur moraines was deposited during a major Holocene re‐advance of Skeiðarárjökull. The moraine ridge is buried by sediments dominated by glacifluvial deposits with an estimated sediment volume of 1.04 km3. 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 Skeiðarársandur, 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.