Base Of Glacier Research Articles

Ra isotope perspective on the hydrology and continuity of permafrost in the high Arctic

The continuous permafrost in the valleys of Svalbard is dotted by pingos, which are small hills formed by the near surface freezing of ascending groundwater. In this study, we used 3H and Ra isotopes to inquire into the sub-surface residence time of groundwater discharging at these pingos. While its low 3H suggests that the pingo-associated groundwater is basically not modern (i.e. older than 60 years), Ra isotopes imply that most water has an underground residence time of several hundred years. This is deduced from the lower than equilibrium ratios (activity ratios<21.7) of the long-lived to short-lived 226Ra/223Ra. Since the freezing age of the main body of permafrost in this area is >4000 years, the presence of younger water at depth suggests that the aquifer has been recharged after permafrost formation, which could take place via faults or through the non-frozen base of wet glaciers. This active hydrology suggests that permafrost in the valleys of Svalbard was at least locally discontinuous during the Late Holocene, with likely further implications to the release of greenhouse gases during the pre-industrial period.

Multi-scale variations of subglacial hydro-mechanical conditions at Kongsvegen glacier, Svalbard

Abstract. The flow of glaciers is largely controlled by changes at the ice–bed interface, where basal slip and sediment deformation drive basal glacier motion. Determining subglacial conditions and their responses to hydraulic forcing remains challenging due to the difficulty of accessing the glacier bed. Here, we monitor the interplay between surface runoff and hydro-mechanical conditions at the base of the Kongsvegen glacier in Svalbard. From July 2021 to August 2022, we measured both subglacial water pressure and till strength. Additionally, we derived median values of subglacial hydraulic gradient and radius of channelized subglacial drainage system from seismic power, recorded at the glacier surface. To characterize the variations in the subglacial conditions caused by changes in surface runoff, we investigate the variations of the following hydro-mechanical properties: measured water pressure, measured sediment ploughing forces, and derived hydraulic gradient and radius, over seasonal, multi-day, and diurnal timescales. We discuss our results in light of existing theories of subglacial hydrology and till mechanics to describe subglacial conditions. We find that during the short, low-melt-rate season in 2021, the subglacial drainage system evolved at equilibrium with runoff, increasing its capacity as the melt season progressed. In contrast, during the long and high-melt-rate season in 2022, the subglacial drainage system evolved transiently to respond to the abrupt and large water supply. We suggest that in the latter configuration, the drainage capacity of the preferential drainage axis was exceeded, promoting the expansion of hydraulically connected regions and local weakening of ice–bed coupling and, hence, enhanced sliding.

What is the primary culprit that causes the "Doomsday Glacier" in Antarctica?

Antarctica, situated in the southernmost part of the earth is surrounded by the Southern Ocean. It has an extremely important role in tuning global climate, both because of its geographic location, and its giant ice mass, that comprises ~90% of the world's ice. In the past decades, the Thwaites Glacier in the Amundsen Sea of West Antarctica is undergoing the fastest recession in the region. The ice loss in Thwaites Glacier is currently responsible for roughly four percent of the global sea-level rise, which has been attributed to climate change and ocean warming. Due to the continuous collapsing and melting of Thwaites Glacier and the severe threat to humans, scientists gave it a terrifying name "Doomsday Glacier". With increasingly geological and geophysical studies conducted in West Antarctica, geothermal heat flux has been discovered to play a vital role in icesheet retreating. The rapidly retreating Thwaites and Pope glaciers are underlain by areas of largely elevated geothermal heat flow, which relates to the tectonic and magmatic history of the West Antarctic Rift System in this region, suggesting that this area is coupled to the dynamics of the underlying lithosphere. The collapsing and melting of the West Antarctic glaciers are without doubt a realistic and complex issue. From the current geological surveys, the heat flux of the crust of West Antarctica appears to be accelerating, coupled with frequent earthquakes and volcanoes. Geothermal features such as hot water lakes, thermal rivers, and giant ice caves beneath the glaciers have been continuously discovered. Therefore, it is reasonable to speculate that geothermal effects play a significant role in modifying the vast ice masses, causing glacier sliding, cracking, collapsing, and ultimately melting, and create conditions for a warming climate to melt West Antarctic glaciers. Many studies also suggest that warm ocean water is intruding beneath the glaciers across the grounding line, leading to melting of glacier bottom, which has been generally considered to be associated with human-emitted greenhouse gases, but it is thought here not to be a primary factor for glacier melting, but most likely a secondary factor. It is believed that primary and secondary factors, Milankovitch orbits, black body radiation, solar activities, human activities, and other factors are all interconnected to form a feedback loop between the glacier base and the ocean, or even a positive feedback loop, which further accelerates the collapsing and melting of the west Antarctic glaciers

Hydraulic suppression of basal glacier melt in sill fjords

Abstract. Using a conceptual model, we examine how hydraulically controlled exchange flows in silled fjords affect the relationship between the basal glacier melt and the features of warm intermediate Atlantic Water (AW) outside the fjords. We show that an exchange flow can be forced to transit into the hydraulic regime if the AW interface height decreases, the AW temperature increases, or the production of glacially modified water is boosted by subglacial discharge. In the hydraulic regime, the heat transport across the sill becomes a rate-limiting factor for the basal melt, which is suppressed. An interplay between processes near the ice–ocean boundary and the hydraulically controlled exchange flow determines the melt dynamics, and the sensitivity of the basal melt to changes in the AW temperature is reduced. The model results are discussed in relation to observations from the Petermann, Ryder, and 79∘ N glaciers in northern Greenland.

A thermomechanical model for frost heave and subglacial frozen fringe

Ice-infiltrated sediment, or frozen fringe, is responsible for phenomena such as frost heave, ice lenses and metres of debris-rich ice under glaciers. Understanding frozen fringes is important as frost heave is responsible for damaging infrastructure at high latitudes and sediment freeze-on at the base of glaciers can modulate subglacial friction, influencing the rate of global sea level rise. Here we describe the thermomechanics of liquid water flow and freezing in ice-saturated sediments, focusing on the conditions relevant for subglacial environments. The force balance that governs the frozen fringe thickness depends on the weight of the overlying material, the thermomolecular force between ice and sediments across liquid premelted films and the water pressure required by Darcy flow. We combine this mechanical model with an enthalpy method that conserves energy across phase change interfaces on a fixed computational grid. The force balance and enthalpy model together determine the evolution of the frozen fringe thickness and our simulations predict frost heave rates and ice lens spacing. Our model accounts for premelting at ice–sediment contacts, partial ice saturation of the pore space, water flow through the fringe, the thermodynamics of the ice–water–sediment interface and vertical force balance. We explicitly account for the formation of ice lenses, regions of pure ice that cleave the fringe at the depth where the interparticle force vanishes. Our model results allow us to predict the thickness of a frozen fringe and the spacing of ice lenses in subaerial and subglacial sediments.

Unraveling the climate control on debris-free glacier evolution in the Everest region (Nepal, central Himalaya) during the Holocene

Current mass balance and meteorological surveys of Mera glacier located about 30 km south of Mount Everest in Nepal show the dominant role of Asian monsoon precipitation on interannual mass balance variability while temperature controls the altitude of snow-rain threshold. As these observations on mass balance variability only explore the recent decades, studies on paleo glacial extents are useful to investigate the long-term climate forcing on glacier evolution. To do so, we investigated the long-term evolution of the debris-free Mera glacier and a neighbouring small debris-free South Khare glacier. Fifty-one 10Be CRE ages were obtained from samples collected on moraine boulders and roches moutonnées. 10Be CRE ages of the boulders span from the end of the Lateglacial (19.0–11.7 ka) to the Little Ice Age (∼0.6–0.1 ka). The oldest dated moraine in this study was observed at the base of South Khare glacier with an age of 13.6 ± 0.5 ka. The two glaciers subsequently experienced their largest Holocene extent in the Early Holocene with moraines dated to 11.0 ± 0.3 ka at the base of Mera glacier and 10.8 ± 0.5 ka at the base of South Khare glacier. We did not observe any moraine from the Mid-Holocene. During the Late Holocene several glacier advances were recorded around 2.3 ± 0.2 ka, 1.5 ka and then during the last centuries at Mera glacier and around 2.8 ± 0.6 ka, and during the Little Ice Age at South Khare glacier. To explore the links between long-term Nepalese glacier changes and climate, we used oceanic and terrestrial Indian Summer monsoon reconstructions and temperature and precipitation output from two transient global climate models TraCE and LOVECLIM. These climate data outputs were corrected by a reconstruction of the Atlantic Meridional Overturning Circulation (AMOC) over the Holocene and its associated climatic impacts. We also used sensitivity experiments from the IPSL (Institut Pierre Simon Laplace) model to discuss the possible influence of horizontal resolution, land hydrology, vegetation and runoff on changes in Asian summer monsoon. Importantly, we show this long-term Nepalese glacier pattern does not perfectly conform neither to the Indian monsoon precipitation that is documented from terrestrial and marine records nor to temperature and precipitation changes simulated by the models. While the maximum glacier extent in the Early Holocene corresponds to enhanced precipitation documented by proxies and models, the Late Holocene glacier advance remains puzzling. We claim that new paleo glacier records and improved climate simulations are necessary to get a better understanding of past glacier changes and the associated climate dynamics, which might be crucial to gain confidence in both glacier and climate future evolutions.

Hydraulic Conditions for Stick‐Slip Tremor Beneath an Alpine Glacier

AbstractAccumulating evidence suggests that glacier basal motion can produce seismogenic stick‐slip events caused by frictional resistance at the ice‐bed interface. Frequent and subsequent failure of multiple stick‐slip patches may constitute sliding tremor in seismic recordings. We show that during stick‐slip tremor at the base of an Alpine glacier, the released seismic moment increases by an order of magnitude. The tremor emerges during melt‐intensive days and is associated with water pressure peaks in a nearby subglacial channel. We propose an extended slider‐block model that explains the regular occurrence of stick‐slip tremor by coupling seismically sliding patches to surrounding aseismically sliding bed regions. The model predicts that the stick‐slip patches control the movement of their surrounding smoothly sliding bed regions via elastic coupling and stress transfer. Thus, tremor producing stick‐slip patches could affect large‐scale ice flow to a degree, which is underestimated in models, with implications on sea level rise projections.

Glacial Ice Melting Stimulates Heterotrophic Prokaryotes Production on the Getz Ice Shelf in the Amundsen Sea, Antarctica

AbstractExtensive oceanographic data sets were combined with microbiological parameters to elucidate the tight coupling between glacial meltwater and heterotrophic bacterial production (BP) on the Getz Ice Shelf (GtzIS) in the Amundsen Sea. BP in the eastern GtzIS (EG; 85.8 pM Leu. h−1), where basal glacier meltwater upwells, was significantly higher than BP measured in the western GtzIS (WG; 50.6 pM Leu. h−1) and the Amundsen Sea Polynya (ASP; 27.8 pM Leu. h−1). BP in the EG accounted for 49% of primary production, which was greater than that of the WG (10%) and ASP (9.2%). Enhanced BP in the eastern GtzIS was not coupled with phytoplankton biomass, but correlated significantly with the freshwater fraction containing meltwater‐derived dissolved organic carbon (MW‐DOC). These results suggest that warming‐induced glacier melting weakens carbon sequestration efficiency in Antarctic coastal waters by stimulating heterotrophic metabolism that converts MW‐DOC to CO2.

Basal hydrofractures near sticky patches

Basal crevasses are macroscopic structural discontinuities at the base of ice sheets and glaciers that arise by fracture. Motivated by observations and by the mechanics of elastic fracture, we hypothesise that spatial variations in basal stress (in the presence of basal water pressure) can promote and localise basal crevassing. We quantify this process in the theoretical context of linear elastic fracture mechanics. We develop a model evaluating the effect of shear-stress variation on the growth of basal crevasses. Our results indicate that sticky patches promote the propagation of basal crevasses, increase their length of propagation into the ice and, under some conditions, give them curved trajectories that incline upstream. A detailed exploration of the parameter space is conducted to gain a better understanding of the conditions under which sticky-patch-induced basal crevassing is expected beneath ice sheets and glaciers.

Inscriptive studies: Toward a Field Articulation

Inscriptive studies: Toward a Field Articulation Paul Benzon (bio) and Rita Raley (bio) ❖ 1 the Road: machine-generated novel written by, in, and with a “WordCar” during a four-day journey from Brooklyn to New Orleans. Cadillac, GPS, clock, camera, Convolutional Neural Network (CNN), Recurrent Neural Network (RNN), and custom training corpus. Curated output published by Jean Boîte Éditions, 2018 (165 × 236 mm; 146 pp). Ross Goodwin, with the assistance of a friend, family and Google’s Artists and Machine Intelligence Group, 2017. ❖ ANNEX: invented and freely downloadable font based on activist graffiti in Istanbul, used for common political slogans rendered illegible by countermarks, geometric shapes, and jumbled arrangements. North Adams, Massachusetts; 30 cm (letters). Neon, Turkish alphabet, English alphabet. Aslı Çavuşoğlu, with font design by Özer Yalçınkaya, 2020. ❖ Because You Know Ultimately We Will Band A Militia: desert billboards along the Gene Autry Trail documenting the haunted history of settler colonialism and white supremacy. Cahuilla Territory, Palm Springs, California; 33.852444, -116.506083. Billboards, archival images. Xaveria Simmons, 2021. ❖ decomp: multiple copies of Charles Darwin’s On the Origin of Species left to decompose in different biogeoclimatic zones. British Columbia, Canada. Codex, photographs, poems, ecosystems. decomp, Coach House Books, 2013 (9 × 6 in.; 144 pp). Stephen Collis and Jordan Scott, 2013–ongoing. ❖ Future Library: repository of individually authored literary works that waits unpublished for a century. Nordmarka and Oslo, Norway; 59.986689, 10.696737 and 59.912965, 10.75099169. Cultivated forest, print manuscripts (one added each year), library reading room. Katie Paterson, 2014–2114. ❖ Grobari [Gravediggers]: a stack of 3,500 sheets of paper, printed on its sides with images of smoke from fires set by Serbian nationalist football fans and marking the imminent disappearance of the .yu domain. Paper, toner, PDF file, printer set to “borderless printing.” Aleksandra Domanović, 2009. [End Page 223] ❖ Ice Texts: words from Gretel Ehrlich’s The Future of Ice (2005) projected onto the base of glaciers during multiple Cape Farewell expeditions. Svalbard, Norwegian archipelago. Ice, digital projection, inkjet prints. Dave Buckland, 2005–2009. ❖ Print In Process [印刷中]: abandoned pieces of Chinese lead typeset in a geometric, pixelated pattern that is mirrored in paint. Hong Kong; 70 × 50 cm (painting), 31 × 22 cm (type box). Movable type, wood, watercolor and pencil on paper. Carmen Ng and Victor Wong, 2022. ❖ Truth Be Told: a three-word figure of speech covering the face of a building, so large as to be deemed hazardous. Kinderhook, New York; 25 × 160 ft. Vinyl building wrap, public building. Nick Cave, 2020. ❖ Untitled (2016): A sheet of paper, nearly four feet by five feet, covered almost entirely with three layers of marks, dense to the point of inscrutability: black on black on yellow. New York, New York; 42½ × 58 in. Acrylic and ink on paper. Dan Miller, 2016. ❖ Watering the distant, deserting the near IX: sand sifted through a fine stencil to form the words of poem, laid on the gallery floor amid memories and documents of public infrastructure and disappearing water stores. North Adams, Massachusetts. Sand, sodium silicate, carbon dioxide, memories, collected recordings, works on paper. Nasser Alzayani, 2020. ❖ WORKBOOK: single-channel video installation poetically defamiliarizing the spoken English language and thematizing the politics of language. British and American ESL workbooks, Text-to-Speech applications, Google Translate. New York; 7:24. Associated digital project, Triple Canopy, 2019. Jesse Chun, 2018. Shelley Jackson, writer: this appellation holds throughout the arc of her career, from her pioneering work of hypertext fiction, Patchwork Girl (1995), to her most recent novel, Riddance: Or, The Sybil Joines Vocational School for Ghost Speakers and Hearing-Mouth Children (2018). It even holds for her ongoing project, Skin (2003–), a story tattooed, word by word, on the skin of 2,095 people who have agreed to have their bodies incorporated into this “mortal work of art.”1 But is “writer” a sufficient or even adequate appellation for the Jackson who originated the project Snow (2014), which consists of words of a story cut in book type into snow in locations around Brooklyn, photographed before they melt, and circulated on Instagram? “Artist” and “author” also have their limitations—the [End Page 224] former so broad as...

Comparison of ground-based and airborne transient electromagnetic methods for mapping glacial and permafrost environments: Cases from McMurdo Dry Valleys, Antarctica

The transient electromagnetic (TEM) method is a non-invasive geophysical tool well-suited for subsurface imaging in cold and polar regions, where common targets are associated with strong contrasts in electrical resistivity. By imaging the electrical properties of the subsurface, the TEM methods can discriminate between geological units such as frozen ground (permafrost), fresh/saline groundwater systems, and bedrock/glacier ice. In this study, we compare TEM data acquired with ground-based and airborne TEM systems. We demonstrate the mapping capabilities of these two approaches in high latitude polar environments with datasets from Taylor Glacier, Lake Vanda, and Canada Glacier in the McMurdo Dry Valleys of Antarctica. The results show a high consistency between the airborne and ground-based TEM data, both with a high resolution and a deep penetration depth down to hundreds of meters due to the resistive background material, which makes both approaches capable of mapping hydrological systems and identifying the base of glaciers. The airborne TEM approach offers an unmatched spatial data coverage in difficult terrain and a far improved lateral resolution compared to the static ground-based system. The ground-based TEM system offers the possibility for using larger transmitter coils and longer stacking times and therefore has potential for reaching deeper penetration depths. The ground-based TEM approach is hence a valuable tool that can provide consistent imaging results while also being far more accessible in terms of cost and field logistics compared to an airborne TEM campaign.

What controls the surging of Karayaylak glacier in eastern Pamir? New insights from remote sensing data

Glacier surges in the Pamir have been widely documented, but the surge mechanism remains poorly known. The Karayaylak Glacier is the first reported surging glacier in eastern Pamir but different dates and possible triggers were published. In this research, the Karayaylak Glacier was studied using an extensive Landsat and Ziyuan-3 (ZY-3) satellite image set. The active phase initiated in May to June 2014, and experienced a peak velocity of 20.1 ± 0.7 m d−1 in May 2015, terminating in October 2015. During 2014–2015, the reservoir zone experienced an average surface elevation reduction of 33.1 ± 1.5 m, and the receiving zone experienced an average surface elevation gain of 36.8 ± 1.5 m. The large basal sliding during the active phase (2014–2015) was likely driven by high water pressure at the bed in an inefficient drainage system. A large volume of water released at the end of the active phase indicated the drainage at the glacier base became more efficient. The abrupt peak velocity, the short active phase and the changes in drainage suggest that the Karayaylak Glacier surge was controlled by hydrology. The behaviour of the Karayaylak Glacier was similar to that of the Kyagar Glacier and Shispare Glacier in the Karakoram.

Numerical modelling of geothermal heat flux and ice velocity influencing the thermal conditions of the Priestley Glacier trough (northern Victoria Land, Antarctica)

Deep geothermal contributions can affect the thermal equilibrium of glacial systems, which can induce changes in their thermal state. These changes can be influenced by glacier dynamics and by the different ice flow velocities experienced over time, which dictate the static and dynamic interactions with glacial trough bedrock. To assess such interactions and to weight the effects of ice mass thermalisations on bedrock, 2D multistage numerical modelling was performed for Priestley Glacier (an outlet glacier) in the East Antarctic glacial system (northern Victoria Land), which has experienced extreme heat flux variations related to rifting and late Cenozoic volcanism. The thermal evolution of Priestley Glacier over the last ~500 ka was modelled considering the mutual contributions of local and deep thermal sources through a parametric variation in the geothermal heat flux. The ice mass velocity was indirectly taken into account by assuming an ice persistence time over the bedrock under timelled considering the mutual contributions of local and deep thermal sources through a parametric variation in the geothermal heat flux. The ice mass velocity was indirectly taken into account by assuming an ice persistence time over the bedrock under time-dependent modelling conditions. Ice thickness and geothermal heat fluxes, varying from 50 to 120 mW/m2, were conditions are strongly linked in determining the thermal state of the glacier base and consequently its impact on basal erosion. According to the adopted ice stationing levels, heat flux conditions not exceeding 70 mW/m2 are needed for preserving a dry-based glacier only assuming velocity conditions equal to or lower than those observed to date along Priestley Glacier. Assuming increased velocity conditions, the glacier sensitivity to heat fluxes decreases, and high to very high heat fluxes are not sufficient to cause glacier base transitions to wet states.

Surface Expression and Apparent Timing of Subglacial Lake Oscillations Controlled by Viscous Ice Flow

AbstractSubglacial lakes are bodies of water that form at the base of ice sheets and glaciers. Ice‐surface elevation above these lakes responds to water volume changes, providing one of few ways to monitor subglacial hydrological systems. Here, we use numerical models to compare surface elevation‐derived estimates of subglacial‐lake length, water‐volume change, and highstand or lowstand timing with their true values. Because ice flow influences the surface expression of lake‐volume change, the correspondence between these estimates and their true values depends strongly on ice thickness, volume‐change rate, and basal drag coefficient. For many realistic combinations of these factors, viscous relaxation of the ice‐sheet surface can render lake volume‐changes unobservable with altimetry. Our results highlight the need for new estimation methods that account for the effects of ice flow, as well as improvements to current resolution limitations that render some events unobservable with altimetry.

Climatic controls on mountain glacier basal thermal regimes dictate spatial patterns of glacial erosion

Abstract. Climate has been viewed as a primary control on the rates and patterns of glacial erosion, yet our understanding of the mechanisms by which climate influences glacial erosion is limited. We hypothesize that climate controls the patterns of glacial erosion by altering the basal thermal regime of glaciers. The basal thermal regime is a first-order control on the spatial patterns of glacial erosion. Polythermal glaciers contain both cold-based portions that protect bedrock from erosion and warm-based portions that actively erode bedrock. In this study, we model the impact of various climatic conditions on glacier basal thermal regimes and patterns of glacial erosion in mountainous regions. We couple a sliding-dependent glacial erosion model with the Parallel Ice Sheet Model (PISM) to simulate the evolution of the glacier basal thermal regime and glacial erosion in a synthetic landscape. We find that both basal thermal regimes and glacial erosion patterns are sensitive to climatic conditions, and glacial erosion patterns follow the patterns of the basal thermal regime. Cold temperature leads to limited glacial erosion at high elevations due to cold-based conditions. Increasing precipitation can overcome the impact of cold temperature on the basal thermal regime by accumulating thick ice and lowering the melting point of ice at the base of glaciers. High precipitation rates, therefore, tend to cause warm-based conditions at high elevations, resulting in intensive erosion near the peak of the mountain range. Previous studies often assessed the impact of climate on the spatial patterns of glacial erosion by integrating climatic conditions into the equilibrium line altitudes (ELAs) of glaciers, and glacial erosion is suggested to be maximal around the ELA. However, our results show that different climatic conditions produce glaciers with similar ELAs but different patterns of basal thermal regime and glacial erosion, suggesting that there might not be any direct correlation between ELAs and glacial erosion patterns.

Changing friction at the base of an Alpine glacier

Repeating earthquakes are a global phenomenon of tectonic faults. Multiple ruptures on the same fault asperities lead to nearly identical waveforms characteristic for these seismic events. We identify their microseismic counterparts beneath an Alpine glacier, where basal sliding accounts for a significant amount of ice flow. In contrast to tectonic faults, Alpine glacier beds are subject to large variations in sliding velocity and effective normal stresses. This leads to inter- and sub-seasonal variations in released seismic moment from stick–slip asperities, which we explain with the rate-and-state friction formalism. During summer, numerically modelled effective normal stresses at asperities are three times higher than in winter, which increases the local shear resistance by the same factor. Stronger summer asperities therefore tend to form in bed regions well connected to the efficient subglacial drainage system. Moreover, asperities organise themselves into a state of subcriticality, transferring stresses between each other. We argue that this seismic stick–slip behavior has potentially far-reaching consequences for glacier sliding and in particular for catastrophic failure of unstable ice masses.

A cut finite element method for non-Newtonian free surface flows in 2D - application to glacier modelling

In ice sheet and glacier modelling, the Finite Element Method is rapidly gaining popularity. However, constructing and updating meshes for ice sheets and glaciers is a non-trivial and computationally demanding task due to their thin, irregular, and time dependent geometry. In this paper we introduce a novel approach to ice dynamics computations based on the unfitted Finite Element Method CutFEM, which lets the domain boundary cut through elements. By employing CutFEM, complex meshing and remeshing is avoided as the glacier can be immersed in a simple background mesh without loss of accuracy. The ice is modelled as a non-Newtonian, shear-thinning fluid obeying the p-Stokes (full Stokes) equations with the ice atmosphere interface as a moving free surface. A Navier slip boundary condition applies at the glacier base allowing both bedrock and subglacial lakes to be represented. Within the CutFEM framework we develop a strategy for handling non-linear viscosities and thin domains and show how glacier deformation can be modelled using a level set function. In numerical experiments we show that the expected order of accuracy is achieved and that the method is robust with respect to penalty parameters. As an application we compute the velocity field of the Swiss mountain glacier Haut Glacier d'Arolla in 2D with and without an underlying subglacial lake, and simulate the glacier deformation from year 1930 to 1932, with and without surface accumulation and basal melt.

A Multi-Physics Experiment with a Temporary Dense Seismic Array on the Argentière Glacier, French Alps: The RESOLVE Project

AbstractRecent work in the field of cryo-seismology demonstrates that high-frequency (&amp;gt;1 Hz) seismic waves provide key constraints on a wide range of glacier processes, such as basal friction, surface crevassing, or subglacial water flow. Establishing quantitative links between the seismic signal and the processes of interest, however, requires detailed characterization of the wavefield, which, at high frequencies, necessitates the deployment of large and dense seismic arrays. Although dense seismic array monitoring has recently become increasingly common in geophysics, its application to glaciated environments remains limited. Here, we present a dense seismic array experiment made of 98 three-component seismic stations continuously recording during 35 days in early spring 2018 on the Argentière Glacier, French Alps. The seismic dataset is supplemented with a wide range of complementary observations obtained from ground-penetrating radar, drone imagery, Global Navigation Satellite Systems positioning, and in situ measurements of basal glacier sliding velocities and subglacial water discharge. We present first results through conducting spectral analysis, template matching, matched-field processing, and eikonal-wave tomography. We report enhanced spatial resolution on basal stick slip and englacial fracturing sources as well as novel constraints on the heterogeneous nature of the noise field generated by subglacial water flow and on the link between crevasse properties and englacial seismic velocities. We outline in which ways further work using this dataset could help tackle key remaining questions in the field.

Spatiotemporal Variability of Velocity and Influence of Glacier Thickness Using Landsat Imagery: Hunza River Basin, Karakoram Range

The Karakoram Anomaly has been intensively investigated, but the factors that control this anomaly, such as the glacier velocity, topography, and mass balance, remain poorly understood. To improve our understanding of the velocity, topography, and mass balance of the Karakoram Glacier, in this study, the spatiotemporal variability of four glacier velocities in the Hunza Basin of the Karakoram range were surveyed using co-registration of optically sensed images and correlation (COSI-Corr) on Landsat imagery from 1993–2019. The results show that the velocity of the Gulmit Glacier increases with a rising altitude from the glacier terminal. The three other glaciers initially display high velocity, followed by a decrease from the glacier terminal, with the maximum velocity attained in the middle of the glacier. In addition, the Karakoram glaciers produced a slight mass gain, with all mountain glaciers exhibiting clear regional acceleration from 1993–2019. The ice deformation velocity of the Batura Glacier diminished at an average rate of 8.49 %. However, the topography of the glacier base and physical factors require further analysis to determine their contribution to the observed changes in glacier velocity. In the present work, multi-temporal remote sensing image interpretations were carried out to determine glacier kinematics, which could enhance our understanding of glacier change mechanisms.

ASSESSMENT OF THE ACCUMULATION OF GAS HYDRATES UNDER THE GLACIER COVER

. The possible accumulation of gas hydrates during the periods of glaciation was estimated taking into account the processes of gas filtration. Model calculations have shown that the rate of hydrate accumulation depends on the height of the ice sheet, thermophysical and hydrophysical properties of the soil, as well as the temperature regime of the soil. The influence of different values of the thickness of the ice sheet (from 200 to 500 m) and the temperature of the soil surface under the ice sheet (from –5 to 0 °С) was modeled. With an ice sheet thickness of 200 m and a basal temperature of about –2 °C, the stability zone of gas hydrates can spread from 10 m and reach 180 m. With an ice sheet thickness of 500 m, the stability zone can begin from the ground surface and reach 200 m even at a glacier base temperature of about 0 °C. When the thickness of the ice sheet is less than 200 m and the temperature of the base of the glacier is about 0 °C, equilibrium thermobaric conditions are not achieved and the accumulation of gas hydrates in the pore space in the upper 200 m soil layer does not occur. Estimates of hydrate accumulation under glacial cover due to fluid filtration are 0.1 % for thawed and 0.05 % for frozen soil per year.