Glacier System Research Articles

Bayesian inversion of joint SH seismic and seismoelectric data to infer glacier system properties

ABSTRACTIn glacial studies, properties such as glacier thickness and the basement permeability and porosity are key to understand the hydrological and mechanical behaviour of the system. The seismoelectric method could potentially be used to determine key properties of glacial environments. Here we analytically model the generation of seismic and seismoelectric signals by means of a shear horizontal seismic wave source on top of a glacier overlying a porous basement. Considering a one‐dimensional setting, we compute the seismic waves and the electrokinetically induced electric field. We then analyse the sensitivity of the seismic and electromagnetic data to relevant model parameters, namely depth of the glacier bottom, porosity, permeability, shear modulus and saturating water salinity of the glacier basement. Moreover, we study the possibility of inferring these key parameters from a set of very low noise synthetic data, adopting a Bayesian framework to pay particular attention to the uncertainty of the model parameters mentioned above. We tackle the resolution of the probabilistic inverse problem with two strategies: (1) we compute the marginal posterior distributions of each model parameter solving multidimensional integrals numerically and (2) we use a Markov chain Monte Carlo algorithm to retrieve a collection of model parameters that follows the posterior probability density function of the model parameters, given the synthetic data set. Both methodologies are able to obtain the marginal distributions of the parameters and estimate their mean and standard deviation. The Markov chain Monte Carlo algorithm performs better in terms of numerical stability and number of iterations needed to characterize the distributions. The inversion of seismic data alone is not able to constrain the values of porosity and permeability further than the prior distribution. In turn, the inversion of the electric data alone, and the joint inversion of seismic and electric data are useful to constrain these parameters as well as other glacial system properties. Furthermore, the joint inversion reduces the uncertainty of the model parameters estimates and provides more accurate results.

Sediment sources and transport by the Kahiltna Glacier and other catchments along the south side of the Alaska Range, Alaska

AbstractErosion related to glacial activity produces enormous amounts of sediment. However, sediment mobilization in glacial systems is extremely complex. Sediment is derived from headwalls, slopes along the margins of glaciers, and basal erosion; however, the rates and relative contributions of each are unknown. To test and quantify conceptual models for sediment generation and transport in a simple valley glacier system, we collected samples for 10Be analysis from the Kahiltna Glacier, which flows off Denali, the tallest mountain in North America. We collected angular quartz clasts on bedrock ledges from a high mountainside above the equilibrium line altitude (ELA), amalgamated clast samples from medial moraines, and sand samples from the river below the glacier. We also collected sand from nine other rivers along the south flank of the Alaska Range. In the upper catchment of the Kahiltna drainage system, toppling, rockfall, and slab collapse are significant erosional processes. Erosion rates of hundreds of millimeters per thousand years were calculated from 10Be concentrations. The 10Be concentrations in amalgamated samples from medial moraines showed concentrations much lower than those measured from the high mountainside, a result of the incorporation of thick, and effectively unexposed, blocks into the moraine, as well as the incorporation of material from lower-elevation nearby slopes above the moraines. The 10Be sediment samples from downstream of the Kahiltna Glacier terminus showed decreasing concentrations with increasing distance from the moraine, indicating the incorporation of material that was less exposed to cosmic rays, most likely from the glacier base as well as from slopes downstream of the glacier. Taken together, 10Be concentrations in various samples from the Kahiltna drainage system indicated erosion rates of hundreds of millimeters per thousand years, which is typical of tectonically active terrains. We also measured 10Be concentrations from river sediment samples collected from across the south flank of the Alaska Range. Calculation of basinwide weighted erosion rates that incorporated hypsometric curves produced unrealistically high erosion rates, which indicates that the major source of sediment was not exposed to cosmic rays and was primarily derived from the base of glaciers. Moreover, the apparently high erosion rates suggest that parts of each drainage system are not in erosional steady state with respect to cosmogenic isotope accumulation.

Estimation of suspended sediment concentration and meltwater discharge draining from the Chaturangi glacier, Garhwal Himalaya

In this study, we present analysis of stream flow near the snout of Chaturangi glacier during the ablation season (June to September (JJAS)) in the year 2015 with an aim to estimate the sediment and water input into the Bhagirathi River from the glacier. In order to assess the variation in meltwater discharge from Chaturangi glacier and to determine its relationship with suspended sediment concentration (SSC), the meltwater and discharge data were analyzed from near the snout to avoid mixing of water and sediment from other glacier tributaries. The meltwater discharge was measured by area velocity method, and the SSC was calculated by vacuum filtration technique. During the entire ablation season (JJAS), marked seasonal variations were observed in the SSC and meltwater discharge. The higher variation is observed in suspended sediment load (SSL) (Cv = 1.17) than SSC (Cv = 0.54) because computation of SSL includes both discharge (Cv = 0.76) and SSC. The average monthly SSC for JJAS was found to be 0.99, 2.29, 4.20, and 1.84 g l−1, respectively, and average monthly meltwater discharge for same period was observed as 5.83, 14.48, 39.81, and 12.69 m3 s−1, respectively. It suggested that throughout the ablation season, the cumulative percentage delivery of SSC follows meltwater discharge. The average suspended sediment yield (SSY) for the entire ablation season was estimated to be 2264.03 ton/km2, and consequent catchment denudation rate was measured as 0.85 mm. A strong positive correlation (r2 = 0.88), found between the discharge and SSC, revealed that both the parameters are dependent on each other. Our results also suggest that the Chaturangi glacier is a major contributor for transportation of sediment into the Bhagirathi River, compared with other tributaries of the Gangotri glacier system.

Basal thermal regime affects the biogeochemistry of subglacial systems

Abstract. Ice formed in the subglacial environment can contain some of the highest concentrations of solutes, nutrients, and microbes found in glacier systems, which can be released to downstream freshwater and marine ecosystems and glacier forefields. Despite the potential ecological importance of basal ice, our understanding of its spatial and temporal biogeochemical variability remains limited. We hypothesize that the basal thermal regime of glaciers is a dominant control on subglacial biogeochemistry because it influences the degree to which glaciers mobilize material from the underlying substrate and controls the nature and extent of biogeochemical activity that occurs at glacier beds. Here, we characterize the solutes, nutrients, and microbes found in the basal regions of a cold-based glacier and three polythermal glaciers and compare them to those found in overlying glacier ice of meteoric origin. Compared to meteoric glacier ice, basal ice from polythermal glaciers was consistently enriched in major ions, dissolved organic matter (including a specific fraction of humic-like fluorescent material), and microbes and was occasionally enriched in dissolved phosphorus and reduced nitrogen (NH4+) and in a second dissolved component of humic-like fluorescent material. In contrast, the biogeochemistry of basal ice from the cold-based glacier was remarkably similar to that of meteoric glacier ice. These findings suggest that a glacier's basal thermal regime can play an important role in determining the mix of solutes, nutrients, and microbes that are acquired from subglacial substrates or produced in situ.

Deep learning applied to glacier evolution modelling

Abstract. We present a novel approach to simulate and reconstruct annual glacier-wide surface mass balance (SMB) series based on a deep artificial neural network (ANN; i.e. deep learning). This method has been included as the SMB component of an open-source regional glacier evolution model. While most glacier models tend to incorporate more and more physical processes, here we take an alternative approach by creating a parameterized model based on data science. Annual glacier-wide SMBs can be simulated from topo-climatic predictors using either deep learning or Lasso (least absolute shrinkage and selection operator; regularized multilinear regression), whereas the glacier geometry is updated using a glacier-specific parameterization. We compare and cross-validate our nonlinear deep learning SMB model against other standard linear statistical methods on a dataset of 32 French Alpine glaciers. Deep learning is found to outperform linear methods, with improved explained variance (up to +64 % in space and +108 % in time) and accuracy (up to +47 % in space and +58 % in time), resulting in an estimated r2 of 0.77 and a root-mean-square error (RMSE) of 0.51 m w.e. Substantial nonlinear structures are captured by deep learning, with around 35 % of nonlinear behaviour in the temporal dimension. For the glacier geometry evolution, the main uncertainties come from the ice thickness data used to initialize the model. These results should encourage the use of deep learning in glacier modelling as a powerful nonlinear tool, capable of capturing the nonlinearities of the climate and glacier systems, that can serve to reconstruct or simulate SMB time series for individual glaciers in a whole region for past and future climates.

Holocene glacier behavior around the northern Antarctic Peninsula and possible causes

We obtained 49 new 10Be ages that document the activity of the former Northern Antarctic Peninsula Ice Sheet, and subsequently the James Ross Island Ice Cap and nearby glaciers, from the end of the last glacial period until the last ∼100 years. The data indicate that from >11 to ∼8 ka marked recession of glacier systems occurred around James Ross Island, including tidewater and local land-terminating glaciers. Glaciers reached heads of bays and fjords by 8-7 ka. Subsequently, local glaciers were larger than present around (at least) 7.5-7 ka and ∼5-4 ka, at times between 3.9 and 3.6 ka and just after 3 ka, between ∼2.4 and ∼1 ka, and from ∼300 to ∼100 years ago. After deglaciation, the largest local glacier extents occurred between ∼7 ka and ∼4 ka.Comparison with other paleoclimate records, including of sea ice extent, reveals coherent climate changes over ∼15° of latitude. In the early Holocene, most of the time a swath of warmth spanned from southern South America to the Antarctic Peninsula sector. We infer such intervals are times of weakening and/or poleward expansion of the band of stronger westerlies, associated with contraction of the polar vortex. Conversely, increased sea ice and equatorward expansion of the westerlies and the polar vortex favor larger glaciers from Patagonia to the Antarctic Peninsula, which typically occurred after ∼8 ka, although warm stretches did take place. For example, on the Antarctic Peninsula and in Patagonia the interval from 4 to ∼3 ka was typically warm, but conditions were not uniform in either region. We also infer that reduced and expanded glacier extents in Patagonia and the eastern Antarctic Peninsula tend to occur when conditions resemble a persistent positive and negative southern annular mode, respectively.

Deep glacial troughs and stabilizing ridges unveiled beneath the margins of the Antarctic ice sheet

The Antarctic ice sheet has been losing mass over past decades through the accelerated flow of its glaciers, conditioned by ocean temperature and bed topography. Glaciers retreating along retrograde slopes (that is, the bed elevation drops in the inland direction) are potentially unstable, while subglacial ridges slow down the glacial retreat. Despite major advances in the mapping of subglacial bed topography, significant sectors of Antarctica remain poorly resolved and critical spatial details are missing. Here we present a novel, high-resolution and physically based description of Antarctic bed topography using mass conservation. Our results reveal previously unknown basal features with major implications for glacier response to climate change. For example, glaciers flowing across the Transantarctic Mountains are protected by broad, stabilizing ridges. Conversely, in the marine basin of Wilkes Land, East Antarctica, we find retrograde slopes along Ninnis and Denman glaciers, with stabilizing slopes beneath Moscow University, Totten and Lambert glacier system, despite corrections in bed elevation of up to 1 km for the latter. This transformative description of bed topography redefines the high- and lower-risk sectors for rapid sea level rise from Antarctica; it will also significantly impact model projections of sea level rise from Antarctica in the coming centuries.

Bacterial community structure of a glacio-marine system in the Arctic (Ny-Ålesund, Svalbard)

The bacterial community composition of a valley glacier in Svalbard, its pro-glacial channels, and the associated downstream fjord ecosystem was investigated so as to figure out the degree to which downslope transport of microbes from the glacier systems along a hydrological continuum impose an effect on the patterns of diversity in the fjord system. A combination of culture based and high-throughput amplicon sequencing approach was followed which resulted in significant variation (R = 0.873, p = 0.001) in the bacterial community structure between these ecosystems. Dominance of sequences belonging to class β-Proteobacteria was seen in the glacier snow, ice and melt waters (MW) while a relatively higher abundance of OTUs belonging to α-Proteobacteria and Verrucomicrobiae demarcated the fjord waters. Similarity percentage (SIMPER) analysis of the Operational Taxonomic Units (OTUs) showed that OTU 1,105,280 (9.15%) and OTU 331 (6.5%) belonging to Burkholderiaceae (β-proteobacteria) and OTU 101,660 (5.76%) and OTU 520 (5.07%) belonging to Rhodobacteraceae (α-proteobacteria) contributed maximum to the overall dissimilarity between the sampling sites. The bacterial community from the MWs were found to be true signatures of the glacier ecosystem while the Kongsfjorden bacterial fraction mostly represented heterotrophic marine taxa influenced by warm Atlantic waters and presence of organic matter. Significant presence of unknown taxa in the MWs suggests the need to study such unexplored, transient niches for a better understanding of the associated microbial processes. Among the various environmental parameters measured, nutrients (NO3− and SiO42−) were found to exhibit strong association with the MW bacterial community while temperature, trace metals, Cl− and SO42− ions were found to influence the fjord bacterial community. The significant differences in the bacterial community composition between the glacier and the fjord ecosystem suggest the unique nature of these systems which in turn is influenced by the associated environmental parameters.

The marine sedimentary environments of Kongsfjorden, Svalbard: an archive of polar environmental change

Kongsfjorden, a fjord in north-western Svalbard, is characterized by large environmental gradients driven by meltwater processes along the margins of tidewater glaciers and the inflow of relatively warm Atlantic Water, the main heat source for the European Arctic. These factors make Kongsfjorden a key area to investigate changes in the polar climate–ocean–glacier system and to examine the resulting effects on the marine environment. The aim of this paper is to synthesize knowledge about the marine sedimentary environment in Kongsfjorden since the last deglaciation. Fjords act as natural sedimentary traps, archiving information about past and present environmental conditions and changes. Geological studies of Kongsfjorden have demonstrated a good potential for reconstructing palaeoenvironments and establishing baselines values for the natural climate changes in the Arctic. Palaeoceanographic reconstructions reveal rising water temperatures similar to modern temperatures ca. 12 000 years ago. The extent of warm Atlantic Water entering the fjords influences processes at, and the stability of, the margins of the tidewater glaciers. Enhanced inflow may cause accelerated glacial melting that, in consequence, leads to an increase in the sediment flux from the glacial catchments into the fjord, as observed ca. 12 000 years ago and at present. However, responses of sediment flux to modern environmental changes remain poorly understood, hence long-term and monitoring studies are needed to quantify and model the effects of climate warming on the sedimentary environment of Kongsfjorden.

Glacier anomalies and relevant disaster risks on the Tibetan Plateau and surroundings

The Tibetan Plateau and its surroundings contain the largest number of glaciers outside the polar regions. In the past 100 years, the glaciers on the Tibetan Plateau and its surrounding areas have been retreating slowly. Since the 1990s, however, the state of glaciers has undergone abnormal changes. Compared with the data derived from the First Chinese Glacier Inventory (CGI) (1960s−1980s), the glacier volume in China decreased by approximately 20% and the glacier area was reduced by approximately 17.7%, based on the data derived from the Second CGI. In particular, the glacier mass loss of the small glaciers was characterized by an area less than 1 km2 and was more intensive than that of lager glaciers. Abnormal changes in the glaciers on the Tibetan Plateau and the surrounding areas are mainly reflected by the spatial pattern. Through the systematic analysis of the data on glacier area, terminal position, and mass balance changes, it was found that the glacier changes in the region experienced obvious spatial heterogeneity from 1990 to 2010. The “Karakoram glacier anomaly” in the eastern Pamir, Karakoram, and western Kunlun regions has exhibited slight mass stability or even glacier advance. However, the glaciers on the southeastern Tibetan Plateau experienced the most intensive and accelerated shrinkage. On the evaluated timescale, the state of glaciers on the Tibetan Plateau and its surroundings has undergone abnormal changes regarding the loss rate of glacier volume. In the past 50 years, most of the glaciers have had a negative mass balance. Moreover, the mass loss process has intensified, especially since the 1990s. It is estimated that the loss rate of glacier volume from the Tibetan Plateau was as large as −15.6 ± 10.1 Gt/a between 2003 and 2009. In addition to the abnormal changes in spatial patterns and temporal changes, the glaciers exhibited an abnormal change within the glacial system. The most significant variability within the glacier system was the abnormal change in the structure of glacier ice. Another abnormal change within the glacier system was that the glaciers showed a sustained slowdown concomitant with ice thinning. Abnormal warming at high altitudes is an important driver of abnormal changes in glaciers on the Tibetan Plateau and its surroundings. Moreover, these contrasting glacier behaviors on the Tibetan Plateau and surroundings are related to atmospheric circulation processes, especially interactions between the westerlies and the Indian Summer Monsoon. In addition, changes in glaciers on the Tibetan Plateau and its surroundings are closely related to the enhancement of human activities. The South Asian region on the southern slope of the Himalayas acts as a main source of severe anthropogenic aerosol emissions, especially that of black carbon. The black carbon transported from South Asia to the glaciers reduces the glacier’s albedo and thus accelerates glacier melting. As global warming intensifies, the abnormal glacier status will likely lead to more hazards, such as ice collapse and glacial lake outburst floods. To reduce the potential glacial risks on the Tibetan Plateau and surroundings, it is necessary to further strengthen the abilities of glacier monitoring and disaster prevention.

Subglacial controls on dynamic thinning at Trinity-Wykeham Glacier, Prince of Wales Ice Field, Canadian Arctic

ABSTRACTMass loss from glaciers and ice caps represents the largest terrestrial component of current sea level rise. However, our understanding of how the processes governing mass loss will respond to climate warming remains incomplete. This study explores the relationship between surface elevation changes (dh/dt), glacier velocity changes (du/dt), and bedrock topography at the Trinity-Wykeham Glacier system (TWG), Canadian High Arctic, using a range of satellite and airborne datasets. We use measurements of dh/dt from ICESat (2003–2009) and CryoSat-2 (2010–2016) repeat observations to show that rates of surface lowering increased from 4 m yr−1 to 6 m yr−1 across the lowermost 10 km of the TWG. We show that surface flow rates at both Trinity Glacier and Wykeham Glacier doubled over 16 years, during which time the ice front retreated 4.45 km. The combination of thinning, acceleration and retreat of the TWG suggests that a dynamic thinning mechanism is responsible for the observed changes, and we suggest that both glaciers have transitioned from fully grounded to partially floating. Furthermore, by comparing the separate glacier troughs we suggest that the dynamic changes are modulated by both lateral friction from the valley sides and the complex geometry of the bed. Further, the presence of bedrock ridges induces crevassing on the surface and provides a direct link for surface meltwater to reach the bed. We observe supraglacial lakes that drain at the end of summer and are concurrent with a reduction in glacier velocity, suggesting hydrological connections between the surface and the bed significantly impact ice flow. The bedrock topography thus has a primary influence on the nature of the changes in ice dynamics observed over the last decade.

Volume Changes of Elbrus Glaciers From 1997 to 2017

This study describes the analysis of changes in area and volume of the Mt. Elbrus glacier system, Central Caucasus from 1997 to 2017. It is based on helicopter-borne ice thickness measurements, comparison of high-resolution imagery and two digital elevation models (DEMs) with 10 meter resolution. More than 250 km of ground-penetrating radar (GPR) profiles of ice thickness with reliable reflections were obtained. The total volume of Mt. Elbrus glaciers was 5.03±0.85 km3 of ice in 2017. Our results show that 68% of the total ice volume is concentrated below 4000 m a.s.l. where the average ice thickness was 44.6±7.3 m, 18% of the volume lies within 4000-4500 m a.s.l. (thickness of 41.2±7.3 m), and just 14% lies above 4500 m a.s.l. (thickness of 29.7±6.65 m). The glacier-covered area of Mt. Elbrus decreased from 125.76±0.65 km2 in 1997 to 112.20±0.58 km2 in 2017, a reduction of 10.8%. Over the same period the volume decreased by 22.8%. The mass balance of the Elbrus glaciers decreased by -0.55±0.04 m w.e. a-1 from 1997 to 2017. Mass balance on west-oriented glaciers is less negative than on east-and south-oriented glaciers where mass balance is most negative. The mass balance of the east-oriented Djikiugankez glacier decreased at the fastest average rate (-0.97±0.07 m w.e. a-1). This glacier contains 28% of the total Elbrus glacier system ice volume, most of which is concentrated below 4000 m a.s.l. Only one small glacier on the western slope demonstrated mass gain. Our results match well with the long term direct mass balance measurements on the Garabashi glacier on Elbrus which lost 12.58 m w.e. and 12.92±0.95 m w.e. between 1997 and 2017 estimated by glaciological and geodetic method, respectively. The rate of Elbrus glacier mass loss tripled in 1997-2017 compared with the 1957-1997 period.

Viscoelastic Modeling of Nocturnal Thermal Fracturing in a Himalayan Debris‐Covered Glacier

Recent observations suggest that the nocturnal thermal fracturing of ice occurs at relatively warm temperatures (above −15 °C) at a high‐altitude Himalayan glacier system unless the ice is shielded by a debris mantle. Here we estimate the stresses induced by diurnal temperature variations using viscous, elastic, and two viscoelastic models, and various thicknesses of the debris mantle. Only the elastic and visco‐elastic models are in agreement with the observations. The timing and amplitudes of the stresses in the upper 15 cm of the glacier are different among the models despite the ability of each approach to predict a diurnal increase in tension exceeding the critical threshold proposed for crevasse formation. For example, the elastic stress is several times larger than the viscous stress at the ice surface (650 vs. 250 kPa) and reaches its peak up to 5–6 hr later in the night. The time lag is in line with the seismic records, suggesting that the viscous model is not appropriate. Furthermore, a debris layer of ≥50 cm in thickness suppresses the diurnal fluctuations in thermal stress and therefore protects the ice from mechanical damage. We suggest that high‐amplitude diurnal cooling and weak ice properties due to weathering are essential factors that influence thermal fracturing in the Himalayan environment. The ongoing expansion of seismic networks into cryospheric regions, which will be capable of detecting local thermal‐contraction‐induced cracks, in combination with the fact that such cracks can erode and weaken the ice, and thereby serve as meltwater and heat channels, warrants further research to better understand these near‐surface processes and to monitor ice properties.

Processes and patterns of glacier-influenced sedimentation and recent tidewater glacier dynamics in Darbel Bay, western Antarctic Peninsula

AbstractBathymetric data of unprecedented resolution are used to provide insights into former ice dynamics and glacial processes in a western Antarctic Peninsula embayment. An assemblage of submarine glacial landforms, which includes subglacially produced streamlined features and ice-marginal ridges, reveals the former pattern of ice flow and retreat. A group of more than 250 small (< 1–3 m high, 10–20 m wide) and relatively evenly spaced recessional moraines was identified beyond the margin of Philippa Glacier. The small recessional moraines are interpreted to have been produced during short-lived, possibly annual re-advances of a grounded ice margin during overall retreat. This is the first time that these features have been shown to be part of the assemblage of landforms produced by tidewater glaciers on the Antarctic Peninsula. Glacier-terminus changes during the last four decades, mapped from LANDSAT satellite images, were analysed to determine whether the moraines were produced during recent still-stands or re-advances of Philippa Glacier and to further investigate the short-term (annual to decadal) variability in ice-marginal position in tidewater glacier systems. The asynchronous response of individual tidewater glaciers in Darbel Bay is interpreted to be controlled mainly by local topography rather than by glacier catchment-area size.

Dynamic vulnerability revealed in the collapse of an Arctic tidewater glacier

Glacier flow instabilities can rapidly increase sea level through enhanced ice discharge. Surge-type glacier accelerations often occur with a decadal to centennial cyclicity suggesting internal mechanisms responsible. Recently, many surging tidewater glaciers around the Arctic Barents Sea region question whether external forces such as climate can trigger dynamic instabilities. Here, we identify a mechanism in which climate change can instigate surges of Arctic tidewater glaciers. Using satellite and seismic remote sensing observations combined with three-dimensional thermo-mechanical modeling of the January 2009 collapse of the Nathorst Glacier System (NGS) in Svalbard, we show that an underlying condition for instability was basal freezing and associated friction increase under the glacier tongue. In contrast, continued basal sliding further upstream increased driving stresses until eventual and sudden till failure under the tongue. The instability propagated rapidly up-glacier, mobilizing the entire 450 km2 glacier basin over a few days as the till entered an unstable friction regime. Enhanced mass loss during and after the collapse (5–7 fold compared to pre-collapse mass losses) combined with regionally rising equilibrium line altitudes strongly limit mass replenishment of the glacier, suggesting irreversible consequences. Climate plays a paradoxical role as cold glacier thinning and retreat promote basal freezing which increases friction at the tongue by stabilizing an efficient basal drainage system. However, with some of the most intense atmospheric warming on Earth occurring in the Arctic, increased melt water can reduce till strength under tidewater glacier tongues to orchestrate a temporal clustering of surges at decadal timescales, such as those observed in Svalbard at the end of the Little Ice Age. Consequently, basal terminus freezing promotes a dynamic vulnerability to climate change that may be present in many Arctic tidewater glaciers.

Subglacial Water Can Accelerate East Antarctic Glacier Flow

Airborne radar from the Recovery Glacier system demonstrates the importance of characterizing the underlying causes of ice flow speedup to understand how glacial discharge could change in the future.

Automatic detection of calving events from time-lapse imagery at Tunabreen, Svalbard

Abstract. Calving is an important process in glacier systems terminating in the ocean, and more observations are needed to improve our understanding of the undergoing processes and parameterize calving in larger-scale models. Time-lapse cameras are good tools for monitoring calving fronts of glaciers and they have been used widely where conditions are favourable. However, automatic image analysis to detect and calculate the size of calving events has not been developed so far. Here, we present a method that fills this gap using image analysis tools. First, the calving front is segmented. Second, changes between two images are detected and a mask is produced to delimit the calving event. Third, we calculate the area given the front and camera positions as well as camera characteristics. To illustrate our method, we analyse two image time series from two cameras placed at different locations in 2014 and 2015 and compare the automatic detection results to a manual detection. We find a good match when the weather is favourable, but the method fails with dense fog or high illumination conditions. Furthermore, results show that calving events are more likely to occur (i) close to where subglacial meltwater plumes have been observed to rise at the front and (ii) close to one another.

Baikal glacier system, new findings

Three glaciers and other small glacial formations, which are not mentioned in the USSR Catalog of glaciers as well as in any published article, were found in the area of the Verkhneangarsky (upper Angara) Range on satellite images. Earlier, researchers from the Institute of Geography of Siberian Branch of RAS described a group of glaciers on the Baikal Mountains and the Barguzin Range, which together with the above group of the Verkhneangarsky Range are related to the Baikal basin by the climate conditions. Ogdynda-Maskit Glacier has been described on the spot in 2017, while other glaciers and snow patches are to be investigated in situ in 2018. Together with the above Baikal and Barguzin glaciers, new data allow identification of the Baikal Glacial system. The article presents analysis of climate changes in the region. Trends in mean annual temperature range from 1 to 4 °C/50 years, while the same of summer temperatures change from 1 to 3 °C/50 years, but without any evident spatial distribution between them. Another situation takes place in the spatial distribution of precipitation: trends in total precipitation decrease towards the Baikal Lake, while precipitation of the cold period, on the contrary, slightly increases towards the Lake, but with rather small trend – 10–40 mm per 50 years. The last fact confirms the influence of the Baikal basin on the alimentation of glaciers and snow patches on the Verkhneangarsky Range. Currently, glaciers of the Verkhneangarsky Range undergo a slow regression.

Patchy Lakes and Topographic Origin for Fast Flow in the Recovery Glacier System, East Antarctica

The Recovery subglacial basin, with its largest glacier Recovery Glacier, has been identified as potentially the biggest contributor to future sea level rise from East Antarctica. Subglacial lakes along the main trunk have been detected from satellite data, with four giant lakes (Recovery Lakes A, B, C, and D) located at the onset of the fast ice flow (≥15 m/yr) and multiple smaller lakes along the glacier. The presence of subglacial water potentially plays a key role in the control of fast ice flow of Recovery Glacier. We present new insights on the Recovery Lakes from airborne radar data collected in 2013 and 2015. Using an adjusted classification scheme, we show that a single large area consisting of smaller lakes connected by likely saturated sediment, referred to as Lake AB, exists in the originally proposed area of the Recovery Lakes A and B. We estimate that the current size of Lake AB is ∼4,320 km2. Water likely leaks from the western shore of Lake AB lubricating the bed initiating fast ice flow at this location. The difference in the outlines of Lake AB and the Lakes A and B previously derived from surface features suggested that a larger paleolake existed here in the past. From our data, we find Recovery Lake C to be dry; we attribute fast ice flow originating from this area to be due to a topographic step and thus an increase in ice thickness rather than enhanced lubrication at the bed.

Retreating Rate of Chaturangi Glacier, Garhwal Himalaya, India Derived from Kinematic GPS Survey and Satellite Data

The regular monitoring of glaciers is important to determine their retreating rate and mass balance for overall glacier health. Chaturangi glacier, a major inactive tributary of the Gangotri glacier system was selected for the present study due to its dynamic nature and also because there are no previous records of its retreating rates. In order to reconstruct past retreating rates, total area loss, volume change and shift in snout position were measured through multi-temporal satellite data from 1989 to 2016 and kinematic GPS survey from 2015 to 2016. The results obtained from satellite data indicate that in the last 27 years Chaturangi glacier snout has retreated 1172.57 +/- 38.3 m (average = 45.07 +/- 4.31 m/year) with a total area and volume loss of 0.626 +/- 0.001 sq. km and 0.139 km(3) respectively. The field measurements through differential global positioning system survey revealed that the annual retreating rate was 22.84 +/- 0.05 m/year. The large variations in results derived from both the methods are probably because of higher difference in their accuracy. Nevertheless, the results derived from both the methods are in agreement that Chaturangi glacier is retreating at a considerable rate.