Academic literature on the topic 'Forni Glacier'

AbstractGlobal warming and the associated glacier retreat recently revealed the entrance to an ice–rock tunnel, at an altitude of ~3600 m a.s.l., in the uppermost portion of the Forni Glacier in the Central Italian Alps. The tunnel served as an entrance to an Austro-Hungarian cableway station excavated in the rocks during the Great War just behind the frontline. A comprehensive geophysical survey, based on seismic and ground-penetrating radar profiling, was then undertaken to map other possible World War I (WWI) remains still embedded in the ice. The ice–rock interface was reconstructed over the entire saddle and in the uppermost portion of the glacier. A prominent linear reflector was surprisingly similar to the common response of buried pipes. The reflector orientation, almost longitudinal to the slope, does not seem to be compatible with a glacial conduit or with other natural features. Numerical simulations of a series of possible targets constrained interpretation to a partly water-filled rounded shape cavity. The presence of a preserved WWI tunnel connecting Mount Vioz and Punta Linke could be considered a realistic hypothesis. The Forni glacier could be still considered polythermal and comprised of cold ice without basal sliding in its top portion.

Abstract. Tourists and hikers visiting glaciers all year round face hazards such as sudden terminus collapses, typical of such a dynamically evolving environment. In this study, we analyzed the potential of different survey techniques to analyze hazards of the Forni Glacier, an important geosite located in Stelvio Park (Italian Alps). We carried out surveys in the 2016 ablation season and compared point clouds generated from an unmanned aerial vehicle (UAV) survey, close-range photogrammetry and terrestrial laser scanning (TLS). To investigate the evolution of glacier hazards and evaluate the glacier thinning rate, we also used UAV data collected in 2014 and a digital elevation model (DEM) created from an aerial photogrammetric survey of 2007. We found that the integration between terrestrial and UAV photogrammetry is ideal for mapping hazards related to the glacier collapse, while TLS is affected by occlusions and is logistically complex in glacial terrain. Photogrammetric techniques can therefore replace TLS for glacier studies and UAV-based DEMs hold potential for becoming a standard tool in the investigation of glacier thickness changes. Based on our data sets, an increase in the size of collapses was found over the study period, and the glacier thinning rates went from 4.55 ± 0.24 m a−1 between 2007 and 2014 to 5.20 ± 1.11 m a−1 between 2014 and 2016.

Abstract. In spite of the quite abundant literature focusing on fine debris deposition over glacier accumulation areas, less attention has been paid to the glacier melting surface. Accordingly, we proposed a novel method based on semi-automatic image analysis to estimate ice albedo from fine debris coverage (d). Our procedure was tested on the surface of a wide Alpine valley glacier (the Forni Glacier, Italy), in summer 2011, 2012 and 2013, acquiring parallel data sets of in situ measurements of ice albedo and high-resolution surface images. Analysis of 51 images yielded d values ranging from 0.01 to 0.63 and albedo was found to vary from 0.06 to 0.32. The estimated d values are in a linear relation with the natural logarithm of measured ice albedo (R = −0.84). The robustness of our approach in evaluating d was analyzed through five sensitivity tests, and we found that it is largely replicable. On the Forni Glacier, we also quantified a mean debris coverage rate (Cr) equal to 6 g m−2 per day during the ablation season of 2013, thus supporting previous studies that describe ongoing darkening phenomena at Alpine debris-free glaciers surface. In addition to debris coverage, we also considered the impact of water (both from melt and rainfall) as a factor that tunes albedo: meltwater occurs during the central hours of the day, decreasing the albedo due to its lower reflectivity; instead, rainfall causes a subsequent mean daily albedo increase slightly higher than 20 %, although it is short-lasting (from 1 to 4 days).

Mountain environments are extremely influenced by climate change but are also often affected by the lack of long and high-quality meteorological data, especially in glaciated areas, which limits the ability to investigate the acting processes at local scale. For this reason, we checked a method to reconstruct high-resolution spatial distribution and temporal evolution of precipitation. The study area is centred on the Forni Glacier area (Central Italian Alps), where an automatic weather station is present since 2005. We set up a model based on monthly homogenised precipitation series and we spatialised climatologies and anomalies on a 30-arc-second-resolution DEM, using Local Weighted Linear Regression (LWLR) and Regression Kriging (RK) of precipitation versus elevation, in order to test the most suitable approach for this complex terrain area. The comparison shows that LWLR has a better reconstruction ability for winter while RK slightly prevails during summer. The results of precipitation spatialisation were compared with station observations and with data collected at the weather station on Forni Glacier, which were not used to calibrate the model. A very good agreement between observed and modelled precipitation records was pointed out for most station sites. The agreement is lower, but encouraging, for Forni Glacier station data.

<p><strong>Abstract.</strong> The application of Structure-from-Motion photogrammetry with ground-based and UAV-based camera stations can be effectively exploited for modeling the topographic surface of Alpine glaciers. Multi-temporal repeated surveys may lead to geometric models that may be applied to analyze the glacier retreat under global warming conditions. Here the case study of Forni Glacier in the Italian Alps is presented. Thanks to the integration of point clouds obtained from the independent photogrammetric processing of ground-based and UAV blocks of images (captured on 2016), a complete 3D reconstruction also including vertical and sub-vertical surfaces has been achieved. This 3D model, compared to a second model obtained from a ground-based photogrammetric survey on September 2017, has been exploited to understand the precursory signal of a big collapse that might have involved tourists and hikers visiting the glacier ice tongue during summer. In addition to some technical aspects related to the acquisition and processing of photogrammetric data of glaciers, this paper highlights how Structure-from-Motion photogrammetry may help evaluate the risk of collapse in Alpine glaciers.</p>

<p><strong>Abstract.</strong> In this paper the use of different types of remote-sensing techniques for monitoring topographic changes of Alpine glaciers is presented and discussed. Close range photogrammetry based on Structure-from-Motion approach is adopted to process images recorded from ground-based and drone-based stations in order to output dense point clouds. These are then directly compared to detect local changes by mean of M3C2 algorithm, while digital elevation models are interpolated to find global ice thinning and retreat. Medium-resolution satellite imagery can be exploited to monitor the glacier evolution at lower resolution but including the development and collapse of large crevasses. A case study concerning the Forni Glacier in the Raethian Alps (Italy) is presented to demonstrate the feasibility of the proposed approach by adopting data sets collected from 2016 to 2018.</p>

The development of methods for quantifying meltwater from glaciated areas is very important for better management of water resources and because of the strong impact of current and expected climate change on the Alpine cryosphere. Radiative fluxes are the main melt-drivers, but they can generally not be derived from in situ measures because glaciers are usually located in remote areas where the number of meteorological stations is very low. For this reason, focusing, as a case study, on one of the few glaciers with a supraglacial automatic weather station (Forni Glacier), we investigated methods based on both satellite records and off-glacier surface observations to estimate incoming short- and long-wave radiation at the glacier surface (SWin and LWin). Specifically, for SWin, we considered CM SAF SARAH satellite gridded surface solar irradiance fields and data modeled by cloud transmissivity parametrized from both CM SAF COMET satellite cloud fractional cover fields and daily temperature range observed at the closest off-glacier station. We then used the latter two data sources to derive LWin too. Finally, we used the estimated SWin and LWin records to assess the errors obtained when introducing estimated rather than measured incoming radiation data to quantify glacier melting by means of an energy balance model. Our results suggest that estimated SWin and LWin records derived from satellite measures are in better agreement with in situ observations than estimated SWin and LWin records parametrized from observations performed at the closest off-glacier station. Moreover, we find that the former estimated records permit a significantly better quantification of glacier melting than the latter estimated ones.

Abstract. Glacier melt conditions (i.e., null surface temperature and positive energy budget) can be assessed by analyzing data acquired by a supraglacial automatic weather station (AWS), such as the station installed on the surface of Forni Glacier (Italian Alps). When an AWS is not present, the assessment of actual melt conditions and the evaluation of the melt amount is more difficult and simple methods based on T-index (or degree days) models are generally applied. These models require the choice of a correct temperature threshold. In fact, melt does not necessarily occur at daily air temperatures higher than 0 °C. In this paper, we applied both energy budget and T-index approaches with the aim of solving this issue. We start by distinguishing between the occurrence of snowmelt and the reduction in snow depth due to actual ablation (from snow depth data recorded by a sonic ranger). Then we find the daily average temperature thresholds (by analyzing temperature data acquired by an AWS on Forni Glacier) which, on the one hand, best capture the occurrence of significant snowmelt conditions and, on the other, make it possible, using the T-index, to quantify the actual snow ablation amount. Finally we investigated the applicability of the mean tropospheric lapse rate to reproduce air temperature conditions at the glacier surface starting from data acquired by weather stations located outside the glacier area. We found that the mean tropospheric lapse rate allows for a good and reliable reconstruction of glacier air temperatures and that the choice of an appropriate temperature threshold in T-index models is a very important issue. From our study, the application of the +0.5 °C temperature threshold allows for a consistent quantification of snow ablation while, instead, for detecting the beginning of the snow melting processes a suitable threshold has proven to be at least −4.6 °C.

Abstract. We investigated the characteristics of sparse and fine debris coverage at the glacier melting surface and its relation to ice albedo. In spite of the abundant literature dealing with dust and black carbon deposition on glacier accumulation areas (i.e.: on snow and firn), few studies that describe the distribution and properties of fine and discontinuous debris and black carbon at the melting surface of glaciers are available. Furthermore, guidelines are needed to standardize field samplings and lab analyses thus permitting comparisons among different glaciers. We developed a protocol to (i) sample fine and sparse supraglacial debris and dust, (ii) quantify their surface coverage and the covering rate, (iii) describe composition and sedimentological properties, (iv) measure ice albedo and (v) identify the relationship between ice albedo and fine debris coverage. The procedure was tested on the Forni Glacier surface (northern Italy), in summer 2011, 2012 and 2013, when the fine debris and dust presence had marked variability in space and time (along the glacier tongue and from the beginning to the end of summer) thus influencing ice albedo: in particular the natural logarithm of albedo was found to depend on the percentage of glacier surface covered by debris. Debris and dust analyses indicate generally a local origin (from nesting rockwalls) and the organic content was locally high. Nevertheless the finding of some cenospheres suggests an anthropic contribution to the superficial dust as well. Moreover, the effect of liquid precipitation on ice albedo was not negligible, but short lasting (from 1 to 4 day long), thus indicating that also other processes affect ice albedo and ice melt rates and then some attention has to be spent analysing frequency and duration of summer rainfalls for better describing albedo and melt variability.

In this PhD Thesis are reported the main results from an interdisciplinary research focused on evaluating impacts and effects of black carbon (BC) on glacier snow and ice melting. With this purpose we selected two glaciers: the Changri Nup glacier (Nepal, Himalaya) and the Forni glacier (Italian Alps). The glaciers have been chosen due to their representativity (geographical setting, size, morphology) and the availability of meteorological and energy data collected at the glacier surface through Automatic Weather Stations (AWSs). In fact on both the glaciers AWSs have been installed in the recent years and they have been running without meaningful interruptions thus permitting to analyze glacier micrometeorology and to evaluate glacier surface energy balance and its variability (data are sampled with a hourly frequency all over the year). Moreover we planned and performed field campaigns to collect snow samples for describing chemical and physical features of soot and dust present in the glacier snow. More precisely, since the Autumn 2005 and AWS has been running at the melting surface of the Forni Glacier (Italian Alps). The AWS is property of UNIMI and it attends the international network SHARE (Stations at High Altitude for Research on the Environment) promoted and managed by EVK2CNR Committee. Within the Ev-K2-CNR Project SHARE on February 2010 an AWS has been installed on the debris-free surface of the Changri Nup Glacier (Nepal, Himalayas, Sagarmatha Nationa Park) at 5,700 m asl to acquire meteorological data and energy fluxes (incoming and outgoing) at the glacier surface. The AWS is property of EvK2CNR Committee. The acquired data permit the calculation of glacier energy balance and high resolution analysis of glacier albedo. In the present study more than 85.000 meteorological parameters, related to the time window 2010-2012 and collected by The Changri Nup AWS, have been analyzed, processed and validated. Average daily parameters estimated at glacier surface have been: temperature: -4.61 °C, relative humidity: 78.47%, atmospheric pressure: 505.6 hPa, SWin: 220 W m-2, SWout:136 W m-2, LWin: 240 W m-2, LWout: 280 W m-2, wind speed: 1.48 m s-1, prevalent wind direction: 183°. Yearly albedo, deriving from SWout/SWin was 0.7, with an average of 0.75 for snow and 0.26 for glacier ice. Instead data from Forni AWS were already available thanks to another PhD research presently on line at the University of Milan. Ablation season at the Changri Nup glacier occurred in summer period, in the monsoon season, when the temperature conditions (T>0°C) and radiation and rain precipitation increase the melting process. Results have been compared with the Alpine site of Forni glacier, the largest Italian valley glacier, located in the Stelvio National Park and characterized by a “strategic” location on the Central-Eastern Alpine sector, able to be reached by southern fluxes and close to the northern Alpine Italian boundary. This part of the research was performed within the SHARE STELVIO project aiming at detecting and quantifying climate change evidences and effects on a sensible area located in the Stelvio National Park – Lombardy sector (600 km2 of area). This project will permit to evaluate composition, quality and variability of high elevation atmosphere and effects on the alpine water resource (i.e. snow, glaciers and meltwater rivers). In both sites the main component deterring melting are positive temperature and shortwave radiation, this latter higher in the Himalaya due to the difference of latitude, altitude and incident direction. Melting season in the Alps is longer than in the Himalaya and in both sites the effect of latent and sensible heat fluxes have a minor effect in driving melting processes. Both sites are characterized by a typical katabatic wind regime. At the Changri Nup glacier surface some ablation stakes have been positioned in the debris free part of the glacier and two of these stakes were located nearby the AWS. Glacier ablation was evaluated through field campaigns twice: February-May 2010 and May-November 2012. The field data allowed to compare measured glacier ablation with melting amount derived from energy balance measurements and to evaluate the reliability of our computations. It was found by previous authors that absorbing aerosols and dust play a key role in varying snow and ice albedo and in driving glacier ablation on several high elevation glaciers. In this study, by coupling energy data (from the AWS) with the atmospheric measurement of BC concentration allow the investigation of the relations among atmosphere and cryosphere and to quantify impacts of atmospheric black carbon deposition on glacial ablation rates. In Himalaya atmospheric observations are carried out at the Nepal Climate Observatory-Pyramid (NCO-P) located at 5,079 m asl near the Pyramid Laboratory Observatory, while at Forni glacier a summer campaign has been held in 2012 at Guasti Hut (c. 3200 m asl). Results at Changri Nup glacier were consistent with the typical estimation available in literature of BC deposition and % of albedo reduction in premonsoon season, where the atmospheric concentration are high. Experimental results reports that at Changri Nup the % of albedo reduction has been 4.26% for an estimated BC deposition in snow of 49 µg kg-1 consistent with the concentration range of BCC in snow of 26.0–68.2 μg kg−1 due to snow density variations between 195–512 kg m−3 as reported in literature. The same estimation has been done at Forni Glacier too, but results were different because the summer BC monitoring campaign detected BC concentrations in the atmosphere typical of free troposphere background conditions, thus in the analyzed period, their deposition didn’t have a predominant effect in driving melting process. To compare the estimated BC deposition in snow deriving from atmospheric measurements, snow samples has been done at the Changri Nup glaciers and the chemical analysis allow to determine a typical premonsoon concentration consistent with literature data and with the experimental estimation done at Changri Nup glaciers. Future step will foresee a further analysis of these results, thanks also to the availability of long term dataset, moreover, in order to improve the knowledge of the effect of dust and aerosol deposition on glacier, more samples will be collected and analyzed.

The Alps, and in general the high mountain areas, in recent decades are under going profound changes due to climate change. The peculiarities and the greater vulnerability of these territories, characterized by complex and delicate balances, are threatened by global warming. In fact, it considerably reduces the habitat of many plant and animal species, pushing them towards ever greater elevations. Once this living zones have reached the tops of the reliefs may no longer be available, and may lead to the disappearance, from these environments, of endemic biodiversity (Hannah et al., 2002). At the same time, however, the progressive debris coverage of the glacial tongues (Deline, 2005; Caccianiga et al., 2011) and the progressive expansion of the proglacial areas, offer new spaces and areas that can be colonised by the vegetation systems and animal communities (Whittaker, 1993). The changes underway in these areas not only affect biological systems, but also geodiversity and the geoheritage of the alpine and mountain environment. “Geodiversity” can be defined simply as “the natural range (diversity) of geological (rocks, minerals, fossils), geomorphological (land form, physical processes) and soil features. It includes their assemblages, relationships, properties, interpretations and systems” (Gray, 2004). For definition of “geodiversity” it follows that an impact on geomorphological processes can affect the local diversity of an area. Examples are the changes in the speed and intensity of processes, such as for example the acceleration of glacial shrinkage, the degradation of permafrost (Deline et al., 2015), the impact of the action of running waters connected to extreme events, the mass wasting processes (Cossart and Fort, 2008; Lane et al., 2017) and the related interactions with biological systems (Eichel, 2015). More in detail in the Alps, but as happens in other mountain ranges, glaciers are shrinking and retreating at ever increasing levels, losing the valley tongues and more and more extensive areas are leaved by the ice. The newly formed proglacial zones are characterized by an abundance of incoherent debris, easily dislocated by the running waters, especially during intense meteorological phenomena (Luino, 2005). These areas, in many cases easily accessible by mountain-goers and not only by expert mountaineers, may therefore present geomorphological dangerous situations, increased by the extremes of meteorological events (for example drought or intense precipitation events). This entails an increase in risks for tourist and even productive activities. The increase in the risk factor for hikers can also derive not only from an increase in danger, for example along the paths, but also from an increase in vulnerability given by sudden changes in weather conditions and the greater difficulty of walking on the paths (Fort, 2015; Pelfini et al., 2007a). The current studies must face the challenge of knowing more in detail the complex interactions that take place in these changing territories, and moreover it is needed to at least partly predict their evolution and behaviour. This challenge has a double value, both scientific, and therefore to broaden the knowledge on the complexity of nature, and civil, because the knowledge of phenomena and the environment allows a more conscious attendance of the high mountain territories. This is the first step for the mitigation of the risk, furthermore, a development that is as environmentally sustainable as possible. Certainly in the coming decades the Alps landscapes will be profoundly different from those of the last century. The progressive reduction of the cryosphere will also have repercussions on many aspects of everyday life of the population that lives not in close contact with the ice giants, but also at a considerable distance from the glacial areas. For example, it has to be considered the availability of drinking water, or the concept of albedo of the snowy areas, a fundamental factor in the climatic feedback processes, or the mountaineering and skiing use of the glaciers. This Doctoral Project fits into this context, that is, to increase knowledge about climatic forcing in high mountain areas and their effect on natural processes. More specifically the attention is focused on the proglacial areas with particular regard to those deglacialized in the last century; but also it was considered the effect of meteorological hazards, like extreme events (mainly rainfall and snowfall) to fragile high-mountain environments. The approach to this study is multifaceted and involves different disciplines: glaciology, geomorphology, dendrochronology, climatology and meteorology, and focuses attention on the interactions between the Earth’s surface and the atmosphere. Particular attention is paid to the meteorological and climatic parameters that can regulate the colonization of proglacial or high mountain areas by pioneer tree species, which are related to the type of substrate, the amount of precipitation, the wind regime to solar radiation and the micrometeorological variables such as sensible and latent heat fluxes (Garavaglia et al., 2010a). The study area focuses on the Forni Valley in high Valtellina (Sondrio, Central Alps, Ortles-Cevedale group), and a comparison with other key sites distributed over the Central-Western Alps, such as Loana Valley in Val Vigezzo (Verbano Cusio Ossola, Central-Western Alps), and the area of Alpe Veglia (Verbano Cusio Ossola, Central-Western Alps, Monte Leone group). These sites are all characterized by a high complexity of orography and different responses to the impacts of climate change. In order to better understand the environment under study, experimental campaigns for measuring meteorological and micrometeorological quantities, were specifically carried out in two of the study sites. The first campaign in the proglacial area of the Forni Glacier, the second in the Alpe Veglia and near the proglacial area of the Aurona Glacier in Val d’Ossola. Both study areas are located in an alpine environment at an altitude between 1740 m a.s.l. of Alpe Veglia and 2552 m a.s.l. of the Forni Glacier, characterised by the absence of vegetation as in the cases of the two proglacial environments, or of pasture with deciduous forest, in the case of Alpe Veglia. The measurement stations installed are equipped both with traditional instruments, such as thermometer, cup anemometer, wind vane, radiometer, barometer and rain gauge, and both with instruments for measuring turbulence in the lowest layer of the atmosphere, or atmospheric boundary-layer, such as the ultrasonic anemometer and the krypton hygrometer. The sites under study, chosen as representative sites of the alpine environment, are characterised by terrain with complex orography, soil, vegetation and degree of anthropization variable in space in a sudden way, and therefore with a dynamics of the atmosphere that is difficult to predict. This has involved the development, parallel to the experimental campaigns, of a numerical modelling both statistical (climatological) and deterministic (meteorological) for the study of the atmosphere and its interaction with the surface. The main points deepened by this work are: a) in the climatology field an indepth study of the precipitation regimes of the last century in the area of the Forni Glacier, and its implications on the run-off and colonization of tree species; b) in the meteorology field an advanced study on atmospheric turbulence measurements in high mountains on the two sites of Alpe Veglia and Forni Glacier. Moreover, thanks to a limited area meteorological model (WRF) it is possible to interpret the dynamics of the atmosphere in detail, always with the aim of correlating the colonization of tree species in the proglacial area and atmospheric processes.