Glacial and proglacial zones of high-mountain regions are among the areas most affected by the ongoing climate warming. Rising temperatures accelerate glacial retreat and the degradation of permafrost, with a consequent increase of instability of steep rock walls, moraines, and slopes. This may increase sediment production that could either contribute to the debris cover of the retreating glaciers, or to an increase in the amount of sediment being transported through the proglacial zone and the more distant fluvial system. The contribution of a proglacial area to the total amount of sediment that exits a basin, however, depends on many factors and it is not yet clear, if sediment supply from such areas will continue to increase or decrease in future. Filling this knowledge-gap is crucial to be able to predict the transport capacity of glacial-fed fluvial systems, especially in relation to possible related hydrogeological hazards.

By analyzing aerial photographs and high-resolution digital surface models from a proglacial area in the Eastern Italian Alps, we demonstrate that these sources of sediment are intimately coupled with the position of the glacier through time; this also applies to the newly formed channel reaches that have evolved following glacial retreat. It follows that sediment sources can be “switched on” or “switched off” in relative short time periods, which are primarily influenced by climate-driven environmental change. Such a pulsed sediment production thus generates waves of sediment that may be entrained by the fluvial system depending on water availability and transport capacity. As such, a detailed and robust forecast of sediment yield for future scenarios may be possible if the spatial and environmental changes associated with glacier retreat and newly formed channel network are monitored and assessed.

How to cite: Savi, S., Comiti, F., and Strecker, M.: Glacial hot spots for sediment supply during global warming: a case study from the Eastern Italian Alps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1089, https://doi.org/10.5194/egusphere-egu23-1089, 2023.

Following the 130 10⁶ m³ detachment of the Sedongpu Glacier (south-eastern Tibet) in 2018, the Sedongpu valley underwent drastic and rapid large-volume landscape changes. Between 2018 and 2022, and in particular during summer 2021, an enormous volume of in total ~335 10⁶ m³ was eroded from the former glacier bed, forming a new canyon of up to 300 m depth, 1 km width and almost 4 km length. The mass was transported into the Yarlung Tsangpo (Brahmaputra) River and further. Several rock-ice avalanches of in total ~150 10⁶ m³ added to the total rock, sediment and ice volume of over 0.6 km³ that were exported from the basin since around 2017. The recent events at Sedongpu Glacier represent a rapid and irreversible process of landscape transformation from a sediment-filled glacier valley to a glacier-free one with a deeply incised canyon, impressively confirming that glaciers are able to protect their soft beds against massive erosion. Once uncovered, the erosion potential of soft glacier beds is here demonstrated to be possibly enormous for some glaciers in terms of volumes and rates. Such erosion could be particularly extreme for fine-grained subglacial sediments and for elevated glacier beds where large amounts of subglacial sediments are stored. The 2018–2022 landscape development at Sedongpu represents an extreme example of rapid paraglacial slope response highlighting extreme glacier erosion potentials and related hazards from debris flows and impacts on rivers. Such consequences of climate change in glacierized mountains have so far not been considered at this magnitude.

How to cite: Kääb, A. and Girod, L.: Rapid and massive 335 million m3 glacier bed erosion after detachment of the Sedongpu Glacier (Tibet), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6052, https://doi.org/10.5194/egusphere-egu23-6052, 2023.

Permafrost-affected rockwalls are increasingly impacted by the effects of climate change and rising air temperature leading to rock slope failures. These events pose a threat for human lives and infrastructure, which underlines the need of better knowledge about their triggering mechanism and propagation.  The aim of this study was to propose a mapping approach of susceptible release areas of rock slope failures and resulting runout distances at a regional scale. This information helps identifying hotspots for subsequent hazard assessment.

To do so, we used an inventory of 1389 rock slope failures (volume > 10² m³)recorded in the Mont-Blanc massif from 2007 to 2019 and determined the topographical and permafrost conditions that are most prone to their triggering using a digital terrain model and a permafrost map. These conditions are used in a multi-criteria GIS approach to identify potential unstable slopes at the French Alps scale. Then, the potential release area map is used as input to map the runout of potential events, using a propagation model based on a normalised area dependant energy line principle. The resulting maps of release and propagation areas will be used to point out human assets (mountaineering routes, high mountain infrastructure, tourism areas) and lakes (that can provoke cascading hazards) which could be impacted by rock slope failure hazards.

This work is a first step to identify hot spots for a regional hazard assessment where more detailed analyses will be required to evaluate potential risks at a local scale.

How to cite: Cathala, M., Magnin, F., Ravanel, L., Luuk, D., Zuanon, N., Berger, F., Bourrier, F., and Philip, D.: Mapping release and propagation areas of permafrost-related rock slope failures to identify hot spots for hazard assessment; French Alps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8183, https://doi.org/10.5194/egusphere-egu23-8183, 2023.

Global warming is affecting the Arctic more significantly as it is warming faster than other places on Earth. The consequences for Arctic as well as sub-Arctic environment are not well understood. Observations in the past decades and climate change impact analysis predicts clear changes in snow cover and snow melt but consequences to frozen soil and related phenomena such as frost quakes are unclear. Frost quakes are non-tectonic seismic events that occur when freezing of water in saturated soils or rocks results in sudden release of seismic energy. Compared to traditional tectonic earthquakes in seismology, frost quakes are much less studied, as they usually occur at random, or less predictable, rarely instrumented locations. Reports and news of frost quakes, resulting in mechanical damage to the pavements, roads and buildings have been received recently from different locations in Finland, Canada and USA and connections between air temperature and frost quakes have been found. The conceptual model of frost quakes is well known but a methodology to predict the occurrence of frost quakes have been missing. In our study, we present a methodology to investigate the connection between thermal stress and frost quakes. Thermal stress is a function of temperature, which can be measured or calculated. We used a hydrological model to calculate snow depth, snow melt rate and soil temperature at different depths in soil. We show that rapid decrease in temperature can cause a thermal stress that is higher than fracture toughness and strength of the soil‐ice mixture. A swarm of frost quakes occurred on 6 January 2016, in in the city of Oulu in Central Finland (sub-Arctic environment). Some of the frost quakes created ruptures in soil, building foundations, and roads. We show that origin of frost quakes was related to rapid decrease in air temperature from -12 °C to –29 °C that created thermal stress in frozen soil and roads which could not withstand the stress.

How to cite: Okkonen, J., Afonin, N., Kokko, E.-R., Kozlovskaya, E., Moisio, K., and Neupauer, R.: Connection between thermal stress and frost quakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12531, https://doi.org/10.5194/egusphere-egu23-12531, 2023.

When glacial dams fail catastrophically, the ensuing glacial lake outburst floods (GLOFs) can cause devastating impacts to downstream environments and infrastructure. Large-impact GLOFs imprint distinct geomorphic features in the landscape that can remain diagnostic for hundreds of years, particularly for GLOFs sourced from moraine-dammed lakes. In this work, we used multi-temporal very-high-resolution-satellite imagery to systematically map the occurrence of impactful GLOFs from moraine-dammed lakes along the Himalayan arc between the Indus and the Salween rivers. Additionally, we binned mapped events by approximate date of occurrence to quantify changes in GLOF frequency through time. This new data set adds over 200 newly mapped GLOFs from ~200 lakes to the 108 events documented in published compilations. We find notable spatial heterogeneity in GLOF hazard along the Himalayan arc. Furthermore, we find that GLOF frequency from moraine-dammed lakes in the last 20 years is markedly lower than earlier time periods from 1970-2000 or from the end of the Little Ice Age to 1970. This decrease in GLOF frequency in recent time is despite continued growth of glacial lakes, likely increases in the frequency of mass movements that commonly trigger GLOFs from moraine-dammed lakes, and mapping bias that likely underestimates GLOF occurrence from earlier time periods.

How to cite: McCoy, S., Jacquet, J., McGrath, D., and Ghuffar, S.: Mapping Himalayan glacial lake outburst flood hazard through time and space, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15703, https://doi.org/10.5194/egusphere-egu23-15703, 2023.

Cryosphere-related hazards are a growing but largely neglected threat for rural settlements, agrarian land use and local livelihoods in the cold-arid Trans-Himalayan region of Ladakh. Despite the growing number of studies on cryosphere-related hazards across High Mountain Asia and other glacierized mountain regions, the occurrence, frequency and magnitude of glacial lake outburst floods (GLOFs) are almost entirely overlooked for the region of Ladakh. Due to the small size and high elevational location of glaciers above 5200 m a.s.l. also the glacial lakes are of small size and some of them are almost permanently ice-covered. In the recent past several GLOF events occurred which destroyed infrastructure and agricultural area. It becomes obvious that even these small glacial lakes might be a permanent threat for local livelihoods and socioeconomic development. This is even more problematic as the number and size of lakes has significantly increased over the past decades. Many of these lakes are dammed by ice-cored moraines which tend to become instable due to climate warming. A comprehensive inventory of glacial lakes for the entire Trans-Himalayan region of Ladakh was carried out. This includes several almost permanently ice-covered high altitude lakes, which have to be detected by visual image interpretation. Changes in the extent and number of glacial lakes have been quantified for the years 1969, 1993, 2000/02 and 2018 in order to assess the potential threat of future GLOFs in the region. A total of 192 glacial lakes cover an area of 5.93 ± 0.70 km² with an estimated water volume of about 61.11 ± 8.5 million m³, including 127 proglacial (PG) and 56 lakes located on recent moraines (RM) were mapped in 2018. The change detection analyses also indicated the disappearance of 22 glacial lakes (decrease by more than 90%) between 1969 and 2018. The lake development of selected former reported GLOF events were analysed in detail to reconstruct lake level changes which possibly indicate earlier GLOF events. Based on high temporal resolution remote sensing data, a sophisticated monitoring concept needs to be realized to indicate the development of short-lived lakes on glaciers or on debris landforms with buried ice or fast glacial lake growth.

How to cite: Schmidt, S., Soheb, M., and Nüsser, M.: Emerging threats: Cryosphere-related hazards in the Trans-Himalaya of Ladakh, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13137, https://doi.org/10.5194/egusphere-egu23-13137, 2023.

As ice thins and retreats due to climate change, glacial lakes can form and grow. Rapid lake drainage can produce devastating outburst floods leading many to propose that hazards from glacial lakes are increasing. Outburst flood compilations do show an increase in the number of events documented over time, however, recent studies attribute such trends to observational bias. This leaves large uncertainty about current and future glacial-lake hazards. Here, we focus on ice-dammed lake drainages in Alaska, as a third of documented events globally occurred in this region. Using multitemporal satellite imagery (Landsat and Sentinel-2), we documented 1150 drainages from 106 lakes over 1985–2020. Accounting for the increase in satellite imagery availability over time, we find no temporal trend in drainage frequency. Furthermore, 70% of lakes decreased in estimated volume and peak discharge since the 1960s, and nearly a third of lakes released earlier through time. These results suggest a decrease in overall regional flood hazard from ice-dammed lakes and motivates an unbiased look at other regions.

How to cite: Rick, B., McGrath, D., McCoy, S., and Armstrong, W.: Regional decrease in hazards from ice-dammed lakes in Alaska since the 1960s, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10799, https://doi.org/10.5194/egusphere-egu23-10799, 2023.

Arctic regions are warming at more than double the global average rate with significant impacts on glaciers and hydrologic systems. Iceland is on the front line of this rapid climate change, with a predicted loss of ~20% of its current ice cap volume by 2100. Much of this meltwater is stored in proglacial lakes at outlet glaciers, which are at risk of draining in glacial lake outburst floods (GLOFs). Most contemporary outburst floods in Iceland have been triggered by subglacial eruptions and geothermal activity; however, GLOFs resulting from mass movement events into lakes are an emerging—yet understudied—hazard. Many of Iceland’s proglacial lakes form in overdeepened basins, storing large volumes of meltwater; expanding lake extent creates more surface area for mass movements to enter; and retreating glaciers remove support from valley walls, increasing rockfall and landslide risk. Several large rockfalls have fallen onto glaciers in the past decades; however, these events may enter lakes as glacier retreat progresses and lakes expand.

We investigate this emerging hazard by predicting proglacial lake evolution and assessing GLOF risk under a future warming climate at three sites in south Iceland. This presentation focuses on the proglacial lake at Fjallsjökull, an outlet glacier of the Vatnajökull ice cap. We present lake volume changes since 1980, derived from bathymetric surveys and mapped lake surface areas. We then estimate future lake volume and extent changes from the present until 2100 based on: 1) local topography derived from bathymetric mapping, ArcticDEM, and subglacial topography from radio-echo sounding surveys; and 2) projected glacier retreat under different climate warming scenarios. Next, we identify potential hazards from mass movement events entering the lake at its current and future extents based on field mapping and remote sensing imagery. Finally, we discuss implications of a glacial outburst flood on downstream communities, infrastructure, and tourism, laying the foundation for future work on hazard assessment and flood modeling. This site is an excellent pilot study for this emerging hazard in Iceland and has significant potential for application to other Icelandic and Arctic glacial lakes.

How to cite: Wells, G. H., Sæmundsson, Þ., Guðmundsson, S., Pálsson, F., Magnússon, E., Hermanns, R. L., and Aðalgeirsdóttir, G.: Future proglacial lake evolution and outburst flood hazard in south Iceland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14598, https://doi.org/10.5194/egusphere-egu23-14598, 2023.

Rivers originating from the Tibetan Plateau (TP) provide water to more than one billion people living downstream. Almost 40% of the TP is currently underlain by permafrost, which serves as both an ice reserve and a flow barrier and is expected to degrade drastically in a warming climate. The hydrological impacts of permafrost thaw across the TP, however, remain poorly understood. Here we quantify the permafrost change on the TP over 1980-2100 and evaluate its hydrological impacts using a physically-based cryospheric-hydrological model. Our results indicate widespread permafrost thaw and prominent ground ice losses under warming. The declining ground ice reserve provides locally important but unsustainable meltwater runoff. In addition, the lowering of the permafrost table and removal of permafrost as a flow barrier would enhance infiltration and raise subsurface storage capacity. The diminished water supply from ground ice melt and enhanced subsurface storage capacity could jointly reduce annual runoff and exacerbate the risk of regional water shortage when facing future droughts. Our findings highlight the important role of permafrost thaw in future water resources management and drought risk assessment across the TP.

How to cite: Wang, T. and Yang, D.: Hydrological implications of pervasive permafrost thaw across the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3046, https://doi.org/10.5194/egusphere-egu23-3046, 2023.