Acceleration and interannual variability of creep rates in mountain permafrost landforms (rock glacier velocities) in the European Alps in 1995–2022

Cryospheric long-term timeseries get increasingly important. To document climate-related effects on long-term viscous creep of ice-rich mountain permafrost, we investigated timeseries (1995–2022) of geodetically-derived Rock Glacier Velocity (RGV), i.e. spatially averaged interannual velocity timeseries related to a rock glacier (RG) unit or part of it. We considered 50 RGV from 43 RGs spatially covering the entire European Alps. Eight of these RGs are destabilized. Results show that RGV are distinctly variable ranging from 0.04 to 6.23 m a$^{−1}$. Acceleration and deceleration at many RGs are highly correlated with similar behaviour over 2.5 decades for 15 timeseries. In addition to a general long-term, warming-induced trend of increasing velocities, three main phases of distinct acceleration (2000–2004, 2008–2015, 2018–2020), interrupted by deceleration or steady state conditions, were identified. The evolution is attributed to climate forcing and underlines the significance of RGV as a product of the Essential Climate Variable (ECV) permafrost. We show that RGV data are valuable as climate indicators, but such data should always be assessed critically considering changing local factors (geomorphic, thermal, hydrologic) and monitoring approaches. To extract a climate signal, larger RGV ensembles should be analysed. Criteria for selecting new RGV-sites are proposed

A REGIONAL-SCALE ROCK GLACIER INVENTORY IN TRENTINO(ITALIAN ALPS)

none6A number of rock glacier inventories were implemented in the framework of PermaNET (Permafrost long-term monitoring network), a project part of the European Territorial Cooperation and co-funded by the European Regional Development Fund (ERDF) in the scope of the Alpine Space Programme (www.alpine-space.eu). Rock glaciers are regarded as one of the most prominent permafrost-related landforms in the alpine territories. A new statistical model and a permafrost distribution map for the entire Alps are partly based on the rock glacier inventories carried out within the project and, in this framework, a new inventory was completed also in the province of Trento. This region is located in the southern part of the Alps and 20% of its territory lies above an altitude of 2000 m a.s.l. The rock glacier inventory is based on analyses carried out in a GIS using a recent (2006) orthophoto (resolution of 0.5m) and a DEM (grid resolution of 2m). First, the rock glaciers were identified using i) the orthophotos and ii) an hillshade derived from the DEM. Then, the outline of the landforms were digitized in the GIS as polygon shapes. The characteristics of the rock glaciers were included in an attribute table linked to the shapes. Our database consist of several descriptive parameters, including that of the Permafrost Evidences Database (PED) of the PermaNET project. However, in agreement with other project partner (e.g. ARPA Valle d'Aosta), we used a number of supplementary parameters, in order to achieve a more complete description of the landforms. The database was partially filled in during the landform digitalization, but most of the information (particularly the morphometric parameters) were obtained from analyses performed in the GIS. In summary, a first group of descriptive parameters of each rock glacier include: location (mountain group and coordinates), altitude (mean and range), slope, length, width, perimeter and area. Other parameters describe additional characteristics, such as: geometry (lobate or tongue shape); general morphology (simple, complex); surface morphology (presence of longitudinal and transverse ridges and furrows and/or hollows and pits); lithology of the feeding area; debris source (talus, till); degree of vegetation coverage, relationships with the local vegetation boundaries and with the glaciers/perennial snowfields located above the rock glacier. Particular attention was paid to the definition of the activity status of the rock glaciers, that were classified as intact (active and inactive landforms containing frozen material) or relict (landforms without frozen material). The assessment was based on i) several evidences visible in the orthophotos and in the DEM, ii) direct field observations carried out in our previous works and iii) field data (i.e. topographic surveys). We used particularly restrictive criteria for classifying the activity status of the rock glaciers from the orthophotos, and this may have resulted in a slightly lower percentage of intact landforms compared to other inventories. Our inventory includes a total of 705 rock glaciers, 134 (19%) classified as intact, the others as relict. They are located at an average altitude 2280 m a.s.l., with a considerable distinction between relict (average altitude of 2190 m a.s.l.) and intact (average altitude of 2660 m a.s.l.) landforms. 50.3% of the rock glaciers face towards N, NE and NW, while 35.2% face towards S, SE and SW. The landforms density (n of rock glacier/km2) is notably different in the various mountain groups of the province, and this seems to be related to the different lithologies that characterize the region. The average surface of the rock glaciers is about 4.7 hectares (0.047 km2). The total area covered by the rock glaciers (33.3 km2) is 1.2% of the entire area of the province located above 1500 m a.s.l., indicating as these landforms are prominent in the periglacial environment of this region.noneSEPPI R.; CARTON A.; ZUMIANI M.; DALL'AMICO M.; ZAMPEDRI G.; RIGON R.Seppi, R.; Carton, Alberto; Zumiani, M.; Dall'Amico, M.; Zampedri, G.; Rigon, R

Osservazioni e studi sul permafrost in Trentino: il progetto PermaNET

Nell’articolo sono presentate le attività di ricerca svolte sul permafrost in Trentino e i principali risultati del progetto PermaNET (Permafrost Long-term Monitoring Network). Sono stati realizzati un catasto dei rock glacier e una carta dell’indice di diffusione del permafrost derivata da un nuovo modello statistico della sua localizzazione. Inoltre, sono state avviate numerose attività di monitoraggio: tra queste, sono in corso misure di temperatura della superficie del suolo e sono proseguite misure topografiche per quantificare lo spostamento di due rock glacier attivi. Sono stati inoltre attrezzati due siti per la misura della temperatura del sottosuolo e dei parametri climatici esterni, allo scopo di valutare la condizione termica del permafrost in funzione dei cambiamenti climatici. La collaborazione al progetto ha consentito di migliorare considerevolmente la conoscenza di questo importante aspetto dell’ambiente alpino del Trentino

Case studies in the European Alps – Amola rock glacier, Val d'Amola, Italian Alps

Topographic measurements are in progress since 2001 on a glacier-derived, active rock glacier (named Amola rock glacier, acronym AmRG, coordinates: 46° 12’ 09” N, 10° 42’ 46” E) located in the Adamello-Presanella group, Central Italian Alps. In addition, data on the ground temperature measured few centimetres below the surface are available since 2004. The displacement data show that some areas of the rock glacier currently (2001-2009) move with velocities ranging from 10 to 20 cm/year, while other sectors can be defined as “dynamically inactive”. The average velocity is significantly variable from year to year, ranging from a minimum of 0.06 m/year (2007-2008) to a maximum of 0.13 m/year (2006-2007), and a slowing trend has been recorded in the last two years. In 2006-2007 a higher rate of displacement seems to be related to a rise in the mean air temperature that probably caused a corresponding rise in the ground temperature. However, in the last year of measurements (2008-2009), an increase in the ground temperature caused by the large amount of snow of the preceding winter, did not result in a corresponding increase of the displacement rate. The dynamic behaviour of this rock glacier reacts very fast to the external forcing, and its response seems to be modulated by the amount and evolution of the snow during winter, due to its effect on the ground temperature. Thus, not only the temperature but also the projected changes in the amount and distribution of precipitation, especially as snow, should be taken into account in assessing the response of this landform to future climate change

Case studies in the European Alps – Maroccaro rock glacier, Val di Genova, Italian Alps

In 2001 we started a topographic study on an active rock glacier (named Maroccaro rock glacier, acronym MaRG, coordinates: 46° 13’ 06” N, 10° 34’ 34” E) located in the Adamello-Presanella massif (Central Italian Alps). Since 2004, also the near-surface ground temperature was measured using a miniature data logger. Our data show that in eight years (2001-2009) MaRG has moved downslope with average velocities ranging from 0.02 to 0.21 m/year. The velocity reaches a maximum in the middle and the lower part of the rock glacier, and decreases towards the upper sector, where the surveyed boulders are almost stationary. A considerable different velocity from year to year has been observed, but no clear trends seem to emerge from the mean annual displacement rate. On the rock glacier the evolution of the ground temperature since 2004 is directly associated with the air temperature and the snow conditions, in terms of thickness and duration of the snowpack. The ground has warmed significantly both in 2007, after a very mild and little snowy winter, and in 2009, after a cold but exceptionally snowy winter. The displacement rate of MaRG seems to rapidly react to the ground temperature variations, apparently without any time delay. The exceptionally snowy winter 2008/09 seems to have played a significant role on the displacement rate, causing a ground temperature increase and, probably, an increase in velocity, which reached its maximum in that year

Little Ice Age mapping as a tool for identifying hazard in the paraglacial environment: The case study of Trentino (Eastern Italian Alps)

The Little Ice Age (LIA) is a well-recognized climatic event during which the glaciers in the Alps advanced and reached their maximum Holocene extent. During their retreat following the LIA, the glaciers left large areas of loose or poorly consolidated glacial deposits in their forelands, which are subject to paraglacial reworking and may represent potential hazards for human infrastructures. In this study, we present a regional scale mapping of the LIA and post-LIA glacial deposits and a reconstruction of the maximum LIA extents of glaciers in the same area. This work is motivated by a local law requiring the classification of areas subject to natural hazards in Trentino (Italian Alps). Results highlight that glaciers shrunk by 63% from the LIA maximum, leaving 30 km2 of unconsolidated deposits, which are subject to geomorphic paraglacial processes. Potentially hazardous consequences can occur, in particular, during high-magnitude instantaneous events, causing debris and mud flows, mass wasting from debris-covered ice, and floods from small moraine-dammed lakes