Rock glaciers as typical periglacial landforms in alpine environments constitute valuable palaeoclimatic indicators due to their connection to the climate-driven permafrost conditions responsible for both their initial formation and continuing activity. In particular for the Late Glacial/Early Holocene transition in cases local morphological evidence for glacial activity is sparse, targeting rock glaciers may successfully complement investigations on contemporaneous landform evolution or climatic variability in mountain regions. The Ben Ohau Range southeast of the Main Divide of the Southern Alps in New Zealand is an example where such conditions prevail. Only few studies focusing on chronological aspects, mostly older ones applying weathering-ring thickness as main dating technique, have been conducted on the rock glaciers occurring in considerable numbers in this selected mountain range to date. Consequently, the chronological data available remain limited.  

Following successful application during a previous pilot study, Schmidt-hammer exposure-age dating (SHD) regarded as suitable calibrated-age dating technique has recently been extensively applied in the Ben Ohau Range. Overarching aim of the related research project is to spatially expand and simultaneously improve the chronological data set for both initial formation and periods of morphodynamic activity of rock glaciers. The obtained chronological data are, furthermore, intended to eventually support the analysis of regional Holocene glacier activity in the Southern Alps.

Additional to SHD-sampling on various rock glaciers, published numerical TCND ¹⁰Be-ages from glacial landforms at two independent sites in the Ben Ohau Range have been utilised to establish a new regional SHD age-calibration equation. Including the abovementioned pilot study SHD age-estimates are now available for eight individual rock glaciers placed in three separate cirques/valley heads located in the middle and southern part of the range. These improved chronological constraints are based on no less than 16,500 sampled boulders on individual transversal rock glacier ridges and SHD age-calibration equation's control points. 

With SHD age-estimates for their initial formation of 11.4 ± 0.4 ka (Duncan Stream), between 9.4 ± 0.9 and 8.6 ± 0.8 ka (Double Basin), and between 11.8 ± 1.6 and 7.3 ± 0.8 ka (Irishman Stream) the studied rock glaciers appear to be significantly older than anticipated and previously reported. Some rock glaciers must have commenced their morphodynamic activity directly around the onset of the Early Holocene, what concurrently indicates that deglaciation of these cirques must have been completed at this point. Because the age difference between the innermost Late Glacial/Early Holocene moraines and the outermost rock glacier ridges sometimes averages only several hundred years, transition from glacial to periglacial processes must have been relatively rapid. With the palaeoclimatic interpretation of this development the significant precipitation gradient east of the Main Divide causing comparatively dry conditions in the middle and southern Ben Ohau Range needs to be taken into account.

Some of the studied rock glaciers are currently active, whereas others need to be classified as inactive. All seem, however, have experienced longer periods of activity during the Holocene.  

How to cite: Winkler, S.: Improved chronological constraints on rock glacier activity in the Ben Ohau Range, Southern Alps/New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2308, https://doi.org/10.5194/egusphere-egu24-2308, 2024.

The Tibetan Plateau is characterized by a high periglacial landscape. The average annual surface temperature is below 0°C over most of the Plateau, so permafrost (permanently frozen ground) is present over most of its extent. Excess ice in the frost-sensitive materials of the active layer, above the permafrost, thaws during the summer and autumn months and freezes during the winter and spring months. These freezing and thawing phenomena lead to cyclic vertical movements of the surface. On the slopes, solifluction phenomena also related to freeze-thaw activity take place, associated to permanent horizontal displacements. Both movements can be measured by spatial geodesy techniques such as Synthetic Aperture Radar Interferometry (InSAR).

The high-altitude Tibetan Plateau, like the Arctic regions, is particularly sensitive to global warming, and recent studies  have documented an apparent acceleration of solifluction processes as well as permanent ground subsidence likely due to ice loss in permafrost. Here, we developed a methodology to analyse hillslope processes from multi-temporal InSAR data to further document this worrying trend, and confirm or not its relation with global and regional temperature increase or with glacier ice loss in Tibet. 

InSAR time series of surface deformation from 16 yr of Envisat (2003-2011) and Sentinel-1 (2014-2020) ESA satellite radar measurements have been built over an 80,000km2 area to study the permafrost evolution of the northeastern Tibetan Plateau. Time series exhibit three trends, (1) a linear trend of continuous deformation, (2) an annual cyclical deformation whose amplitude appears to (3) increase over time. We conducted an analysis of the annual cyclic and cumulative deformation from the InSAR time series and projected those three trends parallel and normal to the line of the greatest slope. Areas with poor constraints were masked based on hillslope aspect from synthetic tests. The measurements (seasonal cycles and cumulative deformation in the slope and normal) were correlated to the lithology, the nature of the surface formations (moraines, alluvial fans, etc.), the altitude, the slope, the curvature, and the orientation of the slopes, in order to characterize the distribution of these processes.

Our change of reference frame strategy proved effective in automatically extracting hillslope processes and quantifying their dynamics. Downward movements affect nearly all terrains, with velocities increasing in line with slope angles. Steeper displacements are observes in unconsolidated, frost-susceptible, and fine-grained sediments, exhibiting higher seasonal amplitude perpendicular to the slope. In contrast, for sedimentary and magmatic rocks that display lower seasonal amplitude, continuous creeping appears to be the primary downward displacement process. Permafrost degradation (long-term subsidence) appears more pronounced at higher altitudes (above 3800m) where one would expect to find the coldest annual average temperatures. We also illustrate significant increases in seasonal amplitude, potentially doubling within 5 years in intermontain basin. These findings suggest a recent degradation of the permafrost and a deepening of the active layer in the northeastern Tibetan Plateau, likely induced by global warming.

How to cite: Watine, H., Daout, S., Lavé, J., and Doin, M.-P.: InSAR monitoring of solifluction and permafrost evolution in the Northeastern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11592, https://doi.org/10.5194/egusphere-egu24-11592, 2024.

Rising temperatures have led to permafrost degradation throughout the Arctic. The melting of excess ground ice leads to a loss of structural support and consolidation of soils. As a consequence, the surface subsides, which, in turn, can accelerate further ground ice loss. Therefore, thaw subsidence is an important metric for monitoring permafrost degradation. With temperature rise reaching twice the Arctic and seven times the global average rate, warming trends in Svalbard are particularly high, leading to severe impacts on permafrost conditions. However, knowledge on subsurface permafrost changes in Svalbard is mostly limited to a few in situ observations. In this study, we aimed to spatially expand research on permafrost degradation by applying a multimethod approach to quantify thaw subsidence in the Bayelva basin (near Ny-Ålesund, Svalbard). First, during a field campaign in summer 2023, we measured Global Navigation Satellite System (GNSS) points and calculated elevation changes since an earlier GNSS survey in 2019. Second, we coregistered and differenced high-resolution digital elevation models (DEMs) for a period of more than 80 years (from 1936, 1995, 2008, 2010, 2019, and 2020) to identify spatial patterns of thaw subsidence over a larger area. Third, we analysed how thaw subsidence relates to various terrain attributes and land cover. By employing these methods, we clearly detected thaw subsidence in the Bayelva basin. The GNSS measurements showed a spatially averaged subsidence of 2.7 cm between 2019 and 2023. With DEM differencing, we observed annual surface subsidence in the order of metres for areas of glacial retreat, in the order of decimetres for moraines, and up to a few centimetres for tundra areas in the glacier foreland. We furthermore detected spatial variations in thaw subsidence throughout the tundra. We conclude that surface subsidence is an ongoing, widespread, and important process in Svalbard’s permafrost landscapes. In this study, we demonstrate the challenges of DEM coregistration in areas with a lack of stable terrain. Nevertheless, our results highlight the potential of GNSS measurements and DEM differencing for quantifying thaw subsidence in the Arctic.

How to cite: Rolf, M., Grünberg, I., Hammar, J., and Boike, J.: Quantifying thaw subsidence in a permafrost landscape (Bayelva basin, Svalbard), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7901, https://doi.org/10.5194/egusphere-egu24-7901, 2024.

Investigating the regional distribution of ice-wedge polygons allows for the estimation of permafrost conditions in periglacial environments, assess its vulnerability to degradation and anticipate how ice-wedge polygons will respond to climate change. Here we investigate the spatial distribution, substrate, and geometric properties of ice-wedge polygons as well as their relationship with other periglacial landforms in Western Greenland near the settlement of Kangerlussuaq. Ice-wedge polygons are networks of interconnected ice-filled fractures that develop in periglacial environments during cyclical drops of temperatures. To investigate the current state of ice-wedge polygons near Kangerlussuaq we conducted a field campaign in July 2023 as part of the Europlanet Transnational Access program. We mapped and characterized ice-wedge polygons using a series of 2004 aerial photographs and our field observations. Polygons in our research area are decameter scale and are found on hillslopes in a sandy loess material that is overlain by a layer of peat and vegetation. We have observed polygons on hillslopes as steep as 36° which suggests that the slope material in our study area is stable and resistant to solifluction. While the polygons themselves did not display any substantial morphological modification between the 2004 aerial photographs and our study, we observed signs of rapid slope modification in the form of active layer detachment slides (ALDS). These relatively small slides (1.2-1.5 × 10² m³) overprinted ice-wedge polygons morphologies downslope, effectively obscuring the polygons without removing them. The frequency of ALDS in permafrost area could increase under the current context of warming temperatures in the Arctic, which would locally affect the ability of any satellite or aerial based studies to detect ice-wedge polygons on the affected hillslopes. We find that polygons are anti correlated with earth hummocks, another type of periglacial landform that develops in poorly drained sites. This suggests that the presence of polygons on a slope modifies the local hydrology by increasing the drainage efficiency, which inhibits the formation of earth hummocks. Our field observations indeed indicate that polygon troughs modify the local drainage and act as water tracks. We observed soil piping and mobilization of small volumes (~1m³) of subsurface material along these troughs. This removal of material is probably facilitated by the absence of coarse material in the sandy loess that composes these slopes. While the extensive vegetation cover in our study area most probably increases the ground resistance to surface erosion via root consolidation and absorption of ground moisture, we suggest that subsurface erosion along polygon troughs will increase if the magnitude of water flow on these hillslopes increases, which should be expected under the current context of wetter-than-normal conditions in the Arctic due to climate change. Finally, we find that 64 % of all polygonised areas we mapped are found on north-west facing hillslopes and 76% are found on slopes steeper than five degrees, which indicate that topography and insolation have been the most likely controls for the development of ice-wedge polygons in this region.

How to cite: Noblet, A., Grau Galofre, A., and Osinski, G. R.: Distribution of ice-wedge polygons in Kangerlussuaq, Western Greenland, and association with other periglacial landforms , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-792, https://doi.org/10.5194/egusphere-egu24-792, 2024.

The deposition of large, resistant boulders on hillslopes and in channels can have an armouring effect on the landscape leading to a decrease in erosion rates, a decrease in the efficiency of downslope sediment transport, and a coeval mismatched increase in slope angle. Such boulder accumulations are a significant component of hillslopes and channels in the southern Appalachian Mountains and influence the landscape's morphology. It has long been speculated that these boulder deposits originated during Quaternary glacial advances under the influence of periglacial processes operating in cold regions south of the maximum extent of the Laurentide Ice Sheet. However, no prior work has tied these features to a specific time or climatically modulated mechanism. By testing and refining the hypothesis of the periglacial origin of these relict boulders and the mechanisms driving their initial deposition and subsequent reworking we hope to contribute to our understanding of the climatically correlated timescales over which contemporary warming can be expected to be a dominating influence on modern boulder armoured periglacial alpine and arctic landscapes.

In this study, we investigated the lifecycle of such boulder deposits by determining cosmogenic ¹⁰Be exposure ages from large boulders on hillslopes and in channels in the Virginia Appalachians, United States. The correlation between the resulting boulder exposure ages (101.7 ± 6.9 ka to 10.8 ± 0.8 ka; n = 23) and the most recent Wisconsin Glacial Stage and subsequent deglaciation (~115 – 11.7 ka) supports their periglacial origin. The lack of exposure ages corresponding to the Last Interglacial Stage or following Wisconsin ice retreat suggests interglacial non-deposition and stability. The absence of exposure ages from the penultimate Illinoian or older Quaternary Glacial Stages suggests that periglacial hillslope processes allow the landscape to be resurfaced with large boulders during each return to cold climate conditions. This cyclic resurfacing of hillslopes and channels is an example of how climatic oscillations insert disequilibrium into the landscape cycle and contributes to our appreciation of the timescales over which climate change may impact boulder landscapes in modern periglacial environments.

How to cite: Fame, M., Chilton, K., Spotila, J., Kelly, M., and Caton, S.: The lifecycle of a relict periglacial boulder landscape, southern Appalachians, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12056, https://doi.org/10.5194/egusphere-egu24-12056, 2024.

Arctic and sub-Arctic terrestrial environments often have bare surfaces, thin and poorly developed soils, large amounts of loose sediment, and low and sparse vegetation. The sensitivity of these sites to modern climate change is reflected, among other things, in an increase in the activity of erosion processes mainly via deflation. Despite the development of modern research tools and monitoring methods, the temporal and spatial changes in the intensity of soil degradation by aeolian processes in high latitude environments is still poorly understood. In this study, we sought to determine soil erosion rates, using anatomical features of Arctic shrubs and dwarf shrubs in northeastern Iceland, central Spitsbergen, and southern Greenland. The main research question we posed was: can the dendrochronological information contained in the anatomy of shrub roots be used to reconstruct soil degradation and erosion histories? We applied dendrochronological techniques to the exposed roots of dwarf willow (Salix herbacea L.), net-leaved willow (Salix reticulata L.), and common juniper (Juniperus communis L.), and estimated surficial erosion based on abrupt changes in cell size and width of annual growth increments in the roots. The accuracy of the dating of erosion processes was checked by comparison with dendrochronological reference scales from specimens collected from undisturbed site. We observed, that after exposure of shrub roots, cell size decreases by at least 50%, with the maximum changes in individual plants exceeding 150-200%. Based on this relationship, we estimated surficial erosion rates for Iceland (1970’s-present), as well as for Spitsbergen and Greenland (1980’s-present). We observed a rapid increase in erosion rates in the latter half of the 1990’s, approaching 5.4 – 6.1 cm/year. Our results confirmed the efficiency of the dendrochronological method we employed, for determining soil erosion rates, even in unforested areas. The method is particularly applicable to low-growing, Arctic dwarf shrubs, which develop measurable growth rings and cells, making them a reliable proxy in soil degradation studies.

The research was founded by a Polish National Science Centre project no. UMO-2021/41/B/ST10/03381 and project no. UMO-2019/35/D/ST10/03137.

How to cite: Owczarek, P., Opała-Owczarek, M., Dagsson-Waldhauserova, P., Schaetzl, R. J., and Migała, K.: Wind erosion rates in the Arctic as recorded the roots of tundra shrubs  – a new dendrochronological approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12880, https://doi.org/10.5194/egusphere-egu24-12880, 2024.

Under current climate conditions the Greenland and Antarctic sheets are rapidly losing mass and these losses are projected to accelerate into the future. Consequently, potential changes in the ice marginal environment across these ice sheets are a future concern. Palaeo-ice sheets, such as the Scandinavian Ice Sheet, provide an opportunity to investigate ice-marginal changes over longer timescales that span a variety of physiographic and geological settings and climate conditions. Landform signatures across Fennoscandia reveal a range of palaeo-ice marginal settings, including lake-terminating, marine-terminating, and higher-altitude environments. This makes the landform record of the Scandinavian Ice Sheet a rich and diverse archive for studying ice margin behaviour. Furthermore, high-resolution digital elevation models (DEMs) that exist for the former bed of this ice sheet allow us to examine ice marginal settings and dynamics in unprecedented and consistent detail across Norway, Sweden and Finland.

We present a geomorphological ice margin dataset of ~56,000 mapped features that categorises each ice margin by its dominant landform type of moraine, hummocky moraine, lateral meltwater channel or glaciofluvial sediment. We then use the morphology of the landforms and overprinting relationships to determine which landforms were likely formed prior to the last deglaciation. The distribution of landform-types in our dataset provides interesting insights into the behaviour of different sectors of the ice sheet. For example, we find ice margins characterised by lateral meltwater channels are almost exclusively found in locations of Quaternary sediment cover, which may indicate that surficial sediment thickness influences their formation, rather than the thermal regime of the ice. We also find ice margins defined by hummocky moraines are more prevalent at higher latitudes. We hypotheses this pattern may be controlled by lower ablation rates at higher latitudes. Additionally, we find contrasts in the density and size of the ice margins between the aquatic and land terminating environments, which results from differences in sedimentation processes within each environment.

How to cite: Dulfer, H., Boyes, B., Dewald, N., Butcher, F., Clark, C., Ely, J., and Hughes, A.: Contrasting regional ice margin dynamics of the Scandinavian Ice Sheet revealed by the landform record, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16439, https://doi.org/10.5194/egusphere-egu24-16439, 2024.

Arctic regions are warming at more than double the global average rate, causing significant changes in cryospheric and hydrologic patterns. As glaciers retreat, meltwater can accumulate in expanding proglacial lakes, which often form in overdeepened basins with large storage capacities and steep valley walls that are prone to paraglacial slope failures. If a mass movement event such as a rockfall or landslide enters the lake, the water can drain in a glacial outburst flood, significantly modifying the landscape. Moreover, many lakes are upstream of infrastructure, communities, and tourism sites, resulting in a high potential societal impact in the event of a flood. This process is a well-documented trigger of floods in glacial regions across the world, but it remains an emerging and understudied hazard in Iceland.

This study investigates past and future proglacial lake evolution and evaluates mass movement-triggered outburst flood risk at two sites in south Iceland. We present: 1) updated maps of lake bathymetry and subglacial topography derived from multibeam sonar and radio-echo sounding surveys, respectively; 2) past lake volume changes and projected future lake extent and volume; and 3) potential slope failure source areas and scenarios of mass movement-triggered outburst floods. These results lay the foundation for future work on flood modeling and hazard planning to mitigate impacts on communities and infrastructure. This project also serves as an excellent pilot study for this emerging hazard in Iceland and has significant potential for application to proglacial lakes in other Arctic and alpine regions.  

How to cite: Wells, G., Sæmundsson, Þ., Pálsson, F., Magnússon, E., Aðalgeirsdóttir, G., and Guðmundsson, S.: Future proglacial lake evolution and outburst flood hazards in south Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12797, https://doi.org/10.5194/egusphere-egu24-12797, 2024.

We investigate the influence of inherited glacier structures on the development of moraine dam morphology over 61 years on four glacial lake dams in the Eastern Himalaya. We compare glacier structures from 1962 Corona imagery with current dam features from 2023 Maxar imagery at Imja, West Barun, Melung and Dang Pu glaciers. From the Corona imagery, maximum glacier extents were identified, along with discrete flow units, ice cliffs, transverse structures, and supraglacial ponds at a 2.5 m resolution. In the Maxar imagery, key dam components were identified including extent of dead ice, hummocky moraines, thermokarst, and surface drainage features and surface structures, mapped at 1 m resolution. Our analysis revealed that former glacier flow unit boundary locations coincide with the development of hydrological features on the dam surface. This was augmented with further analysis of surface elevation change, thermokarst, and surface drainage development using historical aerial imagery, satellite imagery, and DEMs for Imja from 1962 to 2023. We propose that hydrological features exploit relict flow unit boundaries and conclude that inherited glacier structures are key in understanding the development of lake dams that contain dead ice. The glaciological influences on dam features should be included in integrated hazard assessments in glacial settings.

How to cite: Glasser, N., Peacey, M., Reynolds, J., Holt, T., and Hepburn, A.: Inherited glacier structures influence glacial lake dam morphology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17083, https://doi.org/10.5194/egusphere-egu24-17083, 2024.

A glacial lake, characterized by its significant water volume, exists in association with a glacier (under, besides, and in front). They form due to glacial activities influenced by climatic variations. Glacial lakes generally impounded behind weak materials and can rupture suddenly due to various triggers, resulting to catastrophic floods known as Glacial Lake Outburst Floods (GLOFs). Lake’s topography particularity plays a crucial role in its formation and sustenance. Glacial lake related hazards are increasingly gaining attention due to their potential for causing significant damage and loss of life and property in high mountain regions worldwide. Therefore, it is imperative to regularly map and analyze various lake characteristics to understand any potential hazards originating from them.  Considering this, current study aims to present a comprehensive and updated inventory of glacial and high-altitude lakes in the Kargil district of Ladakh and systematically analyzes their types and topographic attributes. With the analysis of recent Sentinel-2 MSI imagery (2022), we identified a total of 355 glacier and high-altitude lakes in the Kargil district, encompassing an area of 4.8 ± 1.2 km². These lakes are divided into four classes mainly based on their relationship with the glaciers: proglacial lakes away from the glacier (PGLA), proglacial lake in contact with glacier (PGLC), supraglacial lakes (SGL) and other lakes (OL). Results reveal that though PGLCs are comparatively low in number (85) but they occupy the largest area share of 60% in total glacial lakes covering an area of 2.88 ± 0.7 km². PGLAs are 138 in number and occupy the second largest area of 0.9 ± 0.2 km². There are large number (103) of SGLs with an area coverage of 0.32 ± 0.07 km². OLs are limited in number (29) and cover 0.6 ± 0.1 km² of area.  The lake sizes range from 0.001 km² to 0.579 km² with an average lake area of 0.013 km² indicating that the lakes in the region are small in size and are in their initial phase of development. The mean elevation for the lakes is 4605 m and notably, ~21% of them predominantly oriented in a southward direction. The majority of lakes are situated on slopes with a gradient ranging 2-8° which reflects their potential to grow in size. It can be deduced from the analysis that the glaciated areas in Kargil region is dominated by large number of PGLC and PGLAs which are likely expand in future posing serious threat to the communities living in immediate proximities to the glaciers. Overall, this research contributes to our understanding of glacier lakes in the Kargil district of the Ladakh region, providing essential data for informed decision-making in order to minimize the glacial lake related hazards.

Keywords: Glacial lake inventory; High altitude lakes; Ladakh Himalaya; Remote sensing; Glacier Lake hazards.

How to cite: Prajapati, M., Garg, P. K., Mukherjee, S., and Gupta, A. K.: Inventory and topographic analysis of glacial and high-altitude lakes in Kargil district, Union Territory of Ladakh, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4926, https://doi.org/10.5194/egusphere-egu24-4926, 2024.