Conference Agenda

Permafrost in the Arctic is experiencing widespread warming and degradation, with consequences ranging from local impacts on hydrology and vegetation to global effects on carbon cycling and climate feedbacks. Snow cover plays a crucial role in modulating the thermal regime of permafrost, acting as an insulating layer that mitigates air temperature fluctuations during winter. Broadly, thicker snow insulates the ground more efficiently, while thinner snow may allow deeper freezing. The insulating effect of snow on soil temperatures and permafrost stability is uncertain due to variations in snow depth, density, and the formation of depth hoar. Our study investigates how the thermal properties of snow vary across spatial and temporal scales and how they influence atmospheric heat transfer to the subsurface. Our research sites span three Arctic permafrost locations with differing climate, surface, and subsurface conditions: Disko Island (West Greenland), Samoylov (Lena River Delta, Siberia), and Bayelva (West Spitsbergen). We present data from long-term observations (Bayelva, Samoylov) and project campaigns (MOMENT – Disko Island), utilizing both automated and manual snow observations.

We report on the physical characteristics of the snowpack, using a combination of automated snow water equivalent measurements, snow density profiles, and time-lapse imagery. Site-specific characteristics—such as warming and refreezing events—create internal and basal ice layers in Svalbard and Greenland, significantly altering the physical structure of the snow. In contrast, the basal snow in Siberia is characterized by thick depth hoar layers with higher insulation properties. These findings suggest potential surprises in permafrost response, driven by non-linear feedbacks and lag effects.

Permafrost cannot be directly observed from space. However, land surface temperature (LST), snow, and land cover information derived from satellite observations can be used as input variables for permafrost models. LST can be used as an indicator of the thermal state of the ground and has, in the last decade, been increasingly used in arctic research and permafrost modelling. Currently, LST datasets based on Moderate Resolution Imaging Spectroradiometer (MODIS) are the most frequently used thanks to their medium spatial resolution (~1km) and extended data coverage (more than 20 years). For example, MODIS LST and ERA5 reanalysis data have been used in the past to force CryoGrid 1, an equilibrium model, designed to compute the mean annual ground temperature at the top of the permafrost table. Using this model, high-resolution (1 km) permafrost maps of the Northern Hemisphere were produced (Obu et al., 2019). A drawback is that MODIS LST products have only been available since 2001, which prevents differentiating multi-decadal climate trends from decadal-scale climate oscillations.

To address this limitation, a new Pan-Arctic LST dataset based on EUMETSAT’s Advanced Very High-Resolution Radiometer (AVHRR) Fundamental Data Record (FDR) published in May 2023 has been developed. The new Pan-Arctic AVHRR LST product covers a period from 1981 to 2021 and has a spatial resolution of approximately 4 km. The newly developed Pan-Arctic AVHRR LST dataset is integrated into the CryoGrid model, enabling a comprehensive comparison between modelling outcomes based on AVHRR LST and MODIS LST across various regions of the Pan-Arctic. Additionally, the AVHRR dataset facilitates a detailed investigation into permafrost dynamics over the past four decades, providing valuable insights into long-term permafrost extent and changes in selected Arctic areas.

Rock glacier motion rates depend on structural, topographic, and climatic factors, while interannual variations are primarily related to those of the thermal state of permafrost. With the objective to provide a novel climate change indicator suitable for mountain permafrost environments, the established parameters of the Essential Climate Variable (ECV) Permafrost, Active Layer Thickness (ALT) and Permafrost Temperature (PT) have been complemented in 2021 by Rock Glacier Velocity (RGV). This context has led to the establishment of RGV Guidelines in 2023 by the Rock Glacier Kinematics and Inventories (RGIK) community.

RGV is an annualized velocity time series documenting the creep rate of mountain permafrost. Time series are derived from various techniques, such as in-situ or remote sensing. Annual ground-based RGV surveys have been undertaken for the past decades in the Swiss Alps on some selected sites, partly in the framework of PERMOS, as well as on a few further rock glaciers in the Alps and worldwide. Air-borne photogrammetry has also been used for longer reconstruction at a multiannual interval. RGV times series mostly show an increasing velocity trend during the past decades. Despite this, methodological challenges to produce consistent RGV time series still need to be overcome. In addition, Synthetic Aperture Radar Interferometry (InSAR) is a satellite-based technique which opens the way to the annual RGV time series production on a large number of sites globally. Within the framework of the ESA CCI Permafrost project, we are analysing the (dis)similarities between the InSAR-based RGV products and those generated with in-situ surveys and optical remote sensing in order to consolidate the approach

In this contribution, we will present the status of RGV generation, mostly based on GNSS and InSAR data. We will also summarize the research needs for implementing an operational worldwide monitoring of RGV as a GCOS ECV permafrost parameter.

Rock glaciers are debris landforms typical of high mountain environments. They can be identified in the landscape by their steep frontal and lateral margins, as well as their lobed surface and the frequent occurrence of ridges and furrows (RGIK, 2023). Their morphology is related to the downslope creeping movement. Over the recent years, the scientific community has highlighted the importance of studying these landforms to improve our understanding of the impacts of climate change on high mountain regions and specifically on alpine permafrost.

The RoDynAlps research project, funded by the Swiss National Foundation and led by the Universities of Fribourg, Lausanne, Zurich and the WSL Institute for Snow and Avalanche Research, aims to better understand the dynamics of rock glaciers in the Swiss Alps. One of the main objectives of the project is to assess the current state of the rock glaciers in the Swiss Alps, by compiling a comprehensive inventory of rock glaciers in the Swiss Alps, including kinematic characterization.

To this aim, standard guidelines developed by a consortium of experts (RGIK, 2023) are currently applied to the whole Switzerland. We present the results obtained in the Bagnes-Hérémence area, in the Valaisan Alps. We found more than 300 rock glaciers between 2000 m and 3200 m a.s.l., covering more than 750 hectares and representing approximately 3.5% of the non-glaciated area (in 2016) above 2000 m. 140 landforms are active, with average deformation rates ranging from several decimeters to one meter per year. Additionally, seven rock glaciers are destabilized, exhibiting abnormal annual displacements of up to 5 meters.

Rock glaciers play a significant role in high mountain watersheds by temporarily storing liquid and solid water. Since the ground ice melting could represent a valuable long-term water resource under the influence of climate change, it is essential to better understand its impacts on rock glacier springs. However, quantifying ground ice content and related processes (thawing, melting, refreezing) is challenging. Hydrogeochemical analysis of rock glacier springs can help gaining more insight. This study examined the spring hydrochemistry and the influence of morphodynamical processes of three active rock glaciers (Monte Prosa A, Ganoni di Schenadüi and Piancabella) in the Swiss Alps.

During the warm season, water samples were collected from rock glacier springs, precipitation, snowpack and seasonal ground ice. Isotopic analysis (δ18O) showed a seasonal increase in δ18O in rock glacier springs, reflecting a shift from snowmelt-fed supply to more 18O-enriched water. Ion chromatography analysis revealed a seasonal increase in ions (e.g. SO42-, Ca2+ and Na+) in rock glacier springs.

To monitor seasonal changes in rock glacier morphodynamics, repeated Unmanned Aerial Vehicle and differential Global Navigation Satellite System surveys were conducted. The comparison between dense point clouds obtained through Structure from Motion photogrammetry showed significant changes in elevation. In particular, over the 2023 warm season, a subsidence was observed in the rooting zone of two rock glaciers (Monte Prosa A and Ganoni di Schenadüi), with thickness losses ranging from about 0.2 to 0.6 m.

These findings suggest that ground ice melting affects both spring hydrochemistry and morphodynamics of the investigated rock glaciers. A relationship was observed between seasonal increases in water chemistry values, indicating an increasing inflow of meltwater from ground ice, and increased deformation (particularly, subsidence that occurred locally at Monte Prosa A and Ganoni di Schenadüi rock glaciers), which could be indicative of increased thawing and melting of ice.

Despite their ubiquity in modern alpine landscapes of the American West and elsewhere, rock glaciers are little understood. Here we document the modern speeds and constrain the ages of rocks on the surface of a prominent rock glacier in Colorado’s West Elk mountains. The glacier is moving at an average of less than 1 m/yr including at its toe where its steep rocky snout is moving into the forest. Ages of rocks on its surface, which record the time at which rock fell from the 300 m headwall, increase steadily from its head to about 13000 years at the terminus. A numerical model that can reproduce these features requires that snow be added to the avalanche cone that feeds the rock glacier in three pulses over this time, each of which generates a down-glacier moving wave of motion. The latest of these is now arriving in the terminus region. The delivery of rock required to create the 2 m thick layer of rock atop the rock glacier and keep the underlying ice from melting implies a headwall back-wearing rate of 4 mm/yr. This is far faster than down wearing of the summit, implying the mountains are eroding sideways.