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Changing glaciers in a changing climate: how vanishing geomorphosites have been driving deep changes in mountain landscapes and environments

La dynamique des glaciers dans le contexte du changement climatique : les géomorphosites révélateurs du bouleversement des paysages et des environnements montagnards
Guglielmina Diolaiuti et Claudio Smiraglia
p. 131-152

Résumés

Au cours des dernières décennies, le retrait mondial des glaciers, des zones alpines à l’Antarctique, a été fréquemment cité comme un signal clair et univoque du réchauffement global. Dans les Alpes, le réchauffement mis en évidence depuis le début des années 80 suit celui qui a lieu à l’échelle mondiale ; cependant son amplitude est plus grande et correspond à une augmentation de la température environ deux fois supérieure à la moyenne globale. Suite à cette évolution rapide du climat, de nombreux petits glaciers pourraient disparaître dans les décennies à venir. Courants dans les Alpes, ces petits glaciers sont également importants en termes de systèmes environnementaux et économiques. La « désintégration » rapide des glaciers alpins a déjà fait l’objet de discussions par la communauté scientifique ; cependant, une attention moindre a été consacrée à leur rôle de géomorphosites en mutation et potentiellement en voie de disparition. Les transformations actuelles de la majeure partie des glaciers alpins, causées par le réchauffement climatique, sont responsables d’impacts environnementaux inattendus qui n’ont été que partiellement étudiés dans les Alpes italiennes. L’article fait état des caractéristiques et de l’évolution de deux géomorphosites glaciaires recensés dans l’« Inventaire des géosites » officiel de la Lombardie (Italie). Cette région des Alpes italiennes compte 348 glaciers qui, en 2003, couvraient une surface d’environ 92 km2. Ils ont perdu environ 21 % de leur superficie entre 1990 et 2003. Les géomorphosites analysés sont le Glacier Forni, le plus étendu d’Italie, et le bassin glaciaire du Val Viola, où plusieurs petits glaciers pourvus de crêtes de moraine bien préservées (datant de l’Holocène supérieur à nos jours) sont observables. Les deux géosites sont situés dans des aires qualifiées de « Sites of Community Importance » d’après les normes de 92/43/EEC ; de plus, le glacier Forni est situé dans une zone protégée, le Parc National du Stelvio. Ces glaciers sont des géomorphosites représentatifs des variations affectant l’ensemble des glaciers alpins ; ils causent non seulement de profonds changements dans la morphologie et l’écologie du paysage de montagne actuel, mais façonnent également des morphologies nouvelles. Ces dernières peuvent être composées de géomorphosites plus petits ayant un certain intérêt culturel et scientifique comme par exemple le thermokarst, les lacs supraglaciaires, les langues de glace couvertes de débris n’ayant fréquemment aucun lien avec le glacier proprement dit, les affleurements rocheux, les lacs au contact de la glace ou endigués par des formations de moraine où flottent des icebergs et où des phénomènes de vêlage sont observables, ou encore les phénomènes de désagrégation de la moraine suite à la fonte des glaces entraînant la formation de coulées de boue et de débris.

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Notes de la rédaction

Article soumis le 19 novembre 2009, accepté le 10 février 2010

Texte intégral

We wish to thank Manuela Pelfini for her collaboration in the study of glacier geomorphosites. The authors also wish to thank the five referees and the editorial staff of the Journal who improved the first draft of this paper. This work was supported financially by San Pellegrino-Levissima under the umbrella of a scientific project aimed at studying the recent changes affecting Val Viola glacierised basin; moreover the analysis of area data for Lombardy glaciers was carried out as part of the “Quantification, Evaluation and Description of Lombardy glacier resource” projects (2004 and 2007) managed by IREALP.

Introduction

1Any variation in climate would lead to destabilisation of environmental and social conditions all around the Planet. These disturbances could jeopardize the conservation of natural ecosystems and the sustainability of socioeconomic systems. Consequently, climate change will also adversely affect - indeed is already affecting - the conservation of World Heritage properties, both natural and cultural. Heritage is an “irreplaceable source of life and inspiration, it is humankind’s legacy from the past, with which we live in the present and pass on to future generations” (UNESCO-World Heritage Center, 2007b). Geo-heritage features, too, could be exposed to the unfavourable effects of changing climate and this is particularly the case with mountain glaciers, which rank among the most fascinating elements of high altitude environments. Mountain glaciers, which with small ice caps represent all the glacier-ice of the Planet outside the polar ice sheet areas, are melting worldwide, and the appearances of some mountainous sites, featuring at national level on Geosite lists and/or at an international level on the World Heritage list because of their exceptional aesthetic beauty, could change deeply. Most mountain glaciers and small ice caps have been in general retreat since the end of the Little Ice Age (LIA), more than 100 years ago (IPCC, 2001); however, in the recent past, glaciers have begun melting at rates that cannot be explained only by natural climate variability (Dyurgerov and Meier, 2000). The melting of glaciers not only has obvious consequences for the values of the sites in which they are located, in terms of natural heritage, but it also impacts on surrounding ecosystems. A recent document by UNESCO-World Heritage Center (2007a) summarised the significant impact predicted by the scientific community if the current trend in warming continues in years to come. The UNESCO scientific team analysed some glacierised World Heritage sites (i.e., Sagarmatha National Park, Nepal; Huascarán National Park, Peru; Ilulissat Icefjord, Denmark; Kilimanjaro National Park, United Republic of Tanzania; Jungfrau-Aletsch-Bietschhorn, Switzerland) to assess the possible consequences of glacier retreat on the environment, the landscape and humankind. In the Alps, such detailed studies are required particularly for sites included at national or regional level on Geosite lists. Glaciers in eight out of the nine European glaciated regions are in retreat. Between 1850 and 1980, glaciers in the European Alps lost approximately one third of their area and one half of their mass, and since 1980 another 20-30% of the ice has melted (European Environment Agency, 2004). About 10% of European glacier mass melted during the heat wave of 2003. If this trend continues - which is very likely - by 2050, some 75% of the glaciers in the Swiss Alps will in all likelihood have disappeared (European Environment Agency, 2004). The consequences of glacier shrinkage on Alpine natural and cultural heritage have not been investigated in any detail and only preliminary studies have so far been made (UNESCO-World Heritage Center, 2007a; Haeberli, 2008). In this paper, we summarise the current trend affecting Alpine glaciers and the direct and indirect consequences on Geosite values and features, with a special focus on two key areas in the Italian Alps: the Forni Glacier and Val Viola, both included in the Geosite list of the Lombardy Region, and both affected by marked and accelerating glacier retreat.

Reduction of glaciers in the last century and ongoing rates of acceleration

2The retreat of glaciers worldwide, from the Alpine areas (Haeberli and Beniston 1998; Beniston, 2000, 2003) to Antarctica (Rott et al., 1996; Cook et al., 2005), in the course of the last few decades, is frequently mentioned as a clear and unambiguous sign of global warming (Oerlemans, 2005). Actually changing glaciers are key indicators of climate and global changes, but they are also vanishing elements in the mountain environment. Glacier shrinkage is particularly severe in the Alps and is probably related to important changes occurring in mid-tropospheric conditions, such as the now widely recognised rapid increase in temperature during recent decades (IPCC, 2001). In fact, in the Alps, atmospheric warming was found to have more than doubled in this period (Böhm et al., 2001), with a significant summer warming, which has been particularly severe since 1970 (Casty et al., 2005). As a result of this rapid climate evolution, many mountain glaciers located at mid elevation could experience fatal reduction and/or could disappear in the next few decades. The terminus fluctuation data, which in the Alps have been collected since the end of the 19th century, show a general retreating trend, with length reduction ranging from a few kilometres (in the case of larger glaciers) to several hundreds of metres (in the case of smaller ones; Hoelzle et al., 2003; Citterio et al., 2007a). The mass balance records, which in the Alps have been measured over the last six decades, indicate strong ice losses, which seem to be accelerating in latter years (from 1985 to the present): in fact, the mean annual mass balance for the decade 1996-2005 is -0.58 m water equivalent (we). This value is more than twice the rate for the period 1986-1995 (-0.25 m we/a) and more than four times the value for the time period 1976-1985 (-0.14 m we/a; Zemp et al., 2006). A detailed study (Holzhauser et al., 2005) of Swiss glaciers, with particular emphasis on the Aletsch Glacier, which is included in the World Heritage List, showed that the largest Alpine glacier has retreated 3.4 km since it reached its maximum length (23 km) at the end of the LIA (19th century). About 1.4 km of this retreat has occurred over the past 56 years and by 2050, if no change in the climate warming trend occurs, it is highly probable that the Aletsch Glacier may have shrunk to its smallest size since the late Bronze Age. However, the strongest climate change effects are expected on smaller glaciers (i.e., glaciers with surface area < 1 km2). These small glaciers are common in the Alps, where they represent 80% of the glacial total and make an important contribution to water resources (Citterio et al., 2007a). In an analysis of the Swiss glacier inventory in 2000 by F. Paul et al. (2004), smaller glaciers were found to show both a wider range of variations than the larger ones, and to contribute more in proportion to the area they represent.

General consequences of Alpine glacier decrease

3In this regard, there is some concern for the near future in the Alps: regional climate models (IPCC, 2001) show that, for a scenario of doubled atmospheric CO2 concentrations, the Alps are likely to experience slightly milder winters with more precipitation, but summers much warmer and drier than at present. These changes will have significant impact on Alpine glaciers, further accelerating their rates of reduction. The most visible impact of this trend will be seen in the aesthetic values of mountains. Melting of the snow will turn the formerly snow-clad mountains into bare, rocky mountains. The Alps will no longer be the ‘abode of snow’. Subsequently, glacier changes will impact in different ways and with different magnitude on landscapes, ecosystems and local climates of mountain areas according to the simple scheme shown in fig. 1.

Fig. 1 – Simplified sketch showing the flow of effects deriving from climate change (main driving factor), to glacier change (driving factor dependent from climate) to the main elements of mountain environment.
Fig. 1 – Schéma simplifié montrant le lien entre le changement climatique global (facteur causal principal) et ses effets sur les principaux éléments du milieu montagnard, par l’intermédiaire des transformations des glaciers (facteur causal second, dérivé du changement climatique).

Fig. 1 – Simplified sketch showing the flow of effects deriving from climate change (main driving factor), to glacier change (driving factor dependent from climate) to the main elements of mountain environment. Fig. 1 – Schéma simplifié montrant le lien entre le changement climatique global (facteur causal principal) et ses effets sur les principaux éléments du milieu montagnard, par l’intermédiaire des transformations des glaciers (facteur causal second, dérivé du changement climatique).

4Any assessment of impact on landscape due to glacier changes must consider that the annual melting of mountainous glaciers drives the hydrological cycles of watersheds. In particular, any increase of glacier melting in the Alps will affect major European rivers such as the Rhine, the Rhône or the Danube and thus pose a threat to Europe’s freshwater supply (UNESCO-World Heritage Center, 2007 b). Besides the landscape and hydrological impact, mountainous ecosystems are also threatened with plant and animal species shifting ranges in order to adapt to the changing environment. The faster the climate warming the greater the loss in biodiversity for species unable to shift at higher elevations. The Geodiversity (sensu Eberhard, 1997; Erikstad, 1999; Gray, 2004; Zwolinski, 2004; Piacente, 2005; Reynard and Coratza, 2007; Serrano and Ruiz-Flaňo, 2007; Panizza, 2009) of mountain areas could be influenced in different and apparently opposite ways by glacier recession: in a first stage, glacier shrinkage gives rise to the development of several minor morphologies (i.e., supraglacial and ice-contact lakes, epiglacial morphologies due to differential ablation processes, paraglacial morphologies). These smaller morphologies, although characterised by a short lifespan, contribute to increasing the geodiversity of the glacierised site at a local scale. On a longer time-scale, on the other hand, the effect of glacier recession is a general decrease of geodiversity due to the complete disappearance of glaciers and of the supra- and paraglacial morphologies. During the first stage of glacier recession (i.e., the current phase of strong decrease) it is also impressive to consider that such vanishing geomorphosites (glaciers) see their scientific value increase, as they are the clearest and unambiguous witnesses of global warming and climate change. Natural systems will not be the only victims of glacier recession: the economies of mountain areas will also be affected. In fact, the tourism industry in the Alps is already concerned by the consequences of climate change and the ongoing reduction in glacier and snow coverage. Up to now, the most detailed studies in this regard have been carried out in Switzerland, as the impact of climate change and glacier retreat on mountain tourism - and consequently on the national economy - are expected to be strongest in that country. Amongst others, H. Elsasser and P. Messerli (2001) focused on climate change and derived impact on winter tourism, suggesting significant consequences for ski resorts in the case of a 300 m rise in the snow line.

5In the case of summer tourism the expected impact of climate change and of glacier retreat are more complex and less clear (Diolaiuti and Smiraglia, 2001a; Cayla, 2009). On the one hand, the warmer summer conditions will provide the opportunity of access to higher elevations to a larger number of trekkers, who will be drawn to visit glacierised areas due to climate change and glacier retreat (people want to see and visit glaciers before they completely disappear). On the other hand, environmental variations due to glacier recession on glacial and periglacial systems are changing features and the level of difficulty of several mountaineering paths (e.g., climbing route, “via-ferrata” assisted climbs, etc.) thus changing in different ways (i.e., increasing and/or decreasing) the number of people frequenting them. Also, summer ski slopes on the surface of some glaciers equipped for this purpose will be affected by climate change, and in most cases this will entail shorter persistence of snow cover and reduced time and space for such activities (see, among the others, Diolaiuti et al., 2006).

The Italian glaciers: a vanishing resource

6About one-third of all Alpine glaciers are located in Italy. A comparison of the various Italian glacier inventories makes it possible to draw a general picture of the changes in Italian glaciers that have taken place over recent decades. M. Citterio et al. (2007a) summarised the recent changes experienced by Italian glaciers: the 1961 Italian glacier inventory (Consiglio Nazionale delle Ricerche and Comitato Glaciologico Italiano, 1959-1961) lists 838 glaciers, 745 of which were inventoried as ‘glaciers’ and 93 as ‘glacierets’. The latter are morphologies formed by glacier ice, deformed by flow (glacier internal structures), and now without deformation or motion due to glacier shrinkage. The 1989 glacier inventory (Biancotti and Motta, 2000) lists 807 glaciers, 706 inventoried as ‘glaciers’ and 101 as ‘glacierets’, thus indicating a loss of 31 glaciers in 28 years (while also underlining an increase in the number of glacierets that points to a further degradation of glacier resources, this type often suggesting the last life-phase of a glacier before its extinction). The total area covered by Italian glaciers shrank from 525 km2 in 1961 to 482 km2 in 1989, a reduction (-43 km2) of about -1.5 km2/a. Moreover, in terms of glacier size distribution, glaciers with a surface area larger than 10 km2 represent only about 0.6% of the total, while 88% have a surface area smaller than 1 km2. More recent quantitative data describing the number and surface areas of all Italian glaciers have not been made available since the 1989 inventory, and similarly, no studies have been conducted on historical geometry changes in a large sample of glaciers and in a timeframe longer than the one between the two national inventories (1961 and 1989) and/or preceding them. To quantify the most recent trend affecting Italian glaciers we can only refer to regional and/or local glacier inventories, which describe the ongoing variations of representative subsets of Italian glaciers.

Recent and ongoing changes in Lombardy region glaciers

7The Lombardy Region in particular offers the opportunity to compare and analyse three regional glacier inventories carried out in 1991 (Servizio Glaciologico Lombardo, 1992), in 1999 (Regione Lombardia, 2004) and in 2003 (Regione Lombardia, 2007). Lombardy is an important glacierised subregion (Santilli et al., 2002), with more than 300 glaciers (about 50% of the total for Italy), which can be considered as representative of all Italian glaciers. In fact, the Lombardy Alps contain not only Italy’s largest glaciers (Adamello, with an area of about 18 km2, and Forni, about 12 km2), but also many medium and small glaciers with a wide range of settings, aspects, altitudes and surface slopes. Moreover, the geometrical feature distribution of Lombardy glaciers agrees with that for most Italian glaciers (Citterio et al., 2007a). We carried out the two most recent inventories of glaciers in the Lombardy Region (Regione Lombardia, 2004, 2007; data source: orthophotos from aerial flights performed in 1999 and 2003, respectively), thus enabling comparison and analysis of the datasets. The 1999 and 2003 records were obtained by combining glacier outlines manually digitised on colour orthophotos (1999 and 2003 flights, Compagnia Generale Riprese Aeree) and Differential Global Positioning System (DGPS) field surveys of glaciers. The 1991 area data were already available in a published regional inventory (Servizio Glaciologico Lombardo, 1992). The total number of glaciers in Lombardy was 334 in 1991 (Servizio Glaciologico Lombardo, 1992), 340 in 1999 and 348 in 2003. The numerical increase is due to glacier fragmentation (i.e., the formation of two or more smaller separate glaciers from a former larger glacier) and reveals an ongoing phase of marked glacier reduction.

8A total of 249 glaciers were recorded in all three data series (1991, 1999 and 2003) and the respective data were compared and analysed. Considering these 249 glaciers common to the three inventories, in 1991 they were spread over an area of 117.4 km2 ± 0.8%; in 1999, the same 249 glaciers covered an area of 104 km2 ± 0.3%, and in 2003 an area of 92.4 km2 ± 0.1%. The total loss in glacierised area from 1991 to 2003 amounted to 25 km2 ± 1%, equal to a loss of about 21% of the glacier coverage in 1991. Moreover, the comparison between the mean yearly value of glacierised area lost over the entire period (1991-2003) and the yearly average calculated for the shorter period (1999-2003) clearly indicates a pattern of acceleration: the rate of retreat rose from -1.58 km2/a (average value for the 1991-1999 period) to -3.1 km2/a (average value for the 1999-2003 period); the mean yearly loss over the whole period (1991-2003) was -2.11 km2/a. This acceleration in the rate of reduction in glacier area was seen in most of the Lombardy glaciers. In Italy and in the Lombardy Region as well, the general shrinkage of glaciers is not only causing the loss of a significant mountain water resource, which is followed by major impact on mountain ecosystems, but is also driving the most marked recent (last century) changes in the Alpine high altitude landscapes. In fact, the disappearance of glaciers means the loss of natural phenomenon, which, due to their scientific attribute and their cultural and economic values, can be considered geomorphosites of primary importance (Pelfini and Smiraglia, 2003).

9The economic value of glaciers has already been mentioned in this paper, in terms of the impact of climate change on glacierised areas and on human activities, including tourism. Moreover glaciers provide meltwater supporting agriculture and electrical power generation. More complicated and difficult is the discussion on the cultural value of glaciers. The complex and various definitions of Culture (which are influenced and driven by historical, philosophical, artistic, scientific, social and anthropological features characterising a human group) broaden the scope of any discussion of the cultural values of glaciers. In fact, it is widely recognised that the evolution and development of humankind is closely linked to the Pleistocenic glacial phases and that the Holocene glaciation too played an important role (Mohen and Elueré, 1997). There is evidence to be found of the interrelations between glaciers and the History, Art, Myths and Science of mountain peoples. Among others, the works of Simler, Ruskin, De Saussure, Segantini, Rousseau, Wolf, Shelley and Agassiz contributed to the culture and literature of glaciers and glacial landscapes. Moreover many legends and myths are linked to glaciers and ice lands (rangingfrom the Wandering Jew to the Lost Valley). Furthermore, there were close connections between glaciers and events which occurred during the First World War. It is widely known that the war lines were marked along the mountain peaks of glacierised mountain groups like the Ortles-Cevedale, Adamello and Marmolada massifs. In that period glaciers were not only scenes of violent battles and conflicts (which culminated in the battle for S. Matteo in 1918, at an altitude of 3684 m) but they were also locations where engineers and technicians performed feats of “glacial engineering” (Viazzi, 1976). Long tunnels were excavated into the ice to catch the enemy (the North face of Cima Trafoi) or to give the soldiers shelter (like the famous ice town of Marmolada); moreover other glacier-derived features (i.e., LIA moraine ridges) were used to build trenches (as was the case at the Forni, Rosole and Cedech glaciers). Evidence of these historical events is easily visible at the surface of alpine glaciers due to their ongoing decreasing phase, which reveals military instruments, arms, barbed wire, remains of shacks and messhuts, grenades and unexploded bombs, together with the bodies of soldiers.

Recent variations in two Lombardy glacier geomorphosites and their impact

10Below we analyse and discuss the features and evolution of two representative Lombardy glacier areas included as geomorphosites in the official “Geosite Inventory” of the Province of Sondrio (Italy; Regione Lombardia, 2008). The geomorphosites analysed are the largest valley glacier of the Italian Alps, Forni (12 km2 in area) in the Ortles-Cevedal Group (fig. 2), and the Val Viola glacierised basin (fig. 3), where different small glaciers with their well-preserved moraine ridges (dating from the upper Holocene to the present) can be found. The Forni and Val Viola geosites are located in territories identified as “Sites of Community Importance” (SCI) under the 92/43/EEC directive; in addition the Forni Glacier is also located in the Stelvio National Park, one of the main Italian protected areas. These glacier geomorphosites are representative of the variations affecting most Italian glaciers and the subsequent effects and impact on the natural and human systems nearby.

Fig. 2 – The Forni Glacier (Ortles-Cevedale group, Central Italian Alps).
Fig. 2 – Le glacier Forni (massif d’Ortles-Cevedale, Alpes centrales italiennes).

Fig. 2 – The Forni Glacier (Ortles-Cevedale group, Central Italian Alps).Fig. 2 – Le glacier Forni (massif d’Ortles-Cevedale, Alpes centrales italiennes).

A: Map of the Forni Glacier. The black dot indicates the supraglacial Automatic Weather Station (AWS); 1: supraglacial debris; 2: rock nunataks. B: Photo of the Forni Glacier. The photo was taken by G. Diolaiuti from the summit of Mount San Matteo (3670 m, the white triangle in the map).
A : Carte du glacier Forni. Le point noir indique l’emplacement de la station météorologique supraglaciaire automatique (AWS) ; 1 : débris supraglaciaires ; 2 : pointements rocheux (nunataks). B : Photo du glacier Forni, prise par G. Diolaiuti depuis le sommet du Mont San Matteo (3670 m, le triangle blanc sur la carte).

Fig. 3 – The Val Viola glaciarised basin (Piazzi-Campo group; Central Italian Alps).
Fig. 3 – Le bassin glaciaire du Val Viola (massif Piazzi-Campo, Alpes centrales italiennes).

Fig. 3 – The Val Viola glaciarised basin (Piazzi-Campo group; Central Italian Alps).Fig. 3 – Le bassin glaciaire du Val Viola (massif Piazzi-Campo, Alpes centrales italiennes).

A: Map of the Val Viola glaciarised basin; 1: 1981 glacier area; 2: 2003 glacier area. B. Photo of the Val Viola glaciarised basin (photo by G. Diolaiuti).
A : Carte du bassin glaciaire du Val Viola ; 1 : extension des glaciers en 1981 ; 2 : domaine englacé en 2003. B : Photo du bassin glaciaire du Val Viola, par G. Diolaiuti.

Forni Glacier changes

11The Forni Glacier lies on the northern slopes below Mt S. Matteo, at an elevation range between 3 670 m and 2 600 m a.s.l. The glacier and the glacierised basin are part of the site of community interest SCI IT2040014 named “Valle e ghiacciaio dei Forni - Val Cedec - Gran Zebru’ - Cevedale”. The SCI manager is the Stelvio National Park. The Forni Glacier has been visited for scientific and tourist purposes (Stoppani, 1908; Smiraglia, 1984 a and b, 1988, 1989; Guglielmin et al., 1995; Diolaiuti and Smiraglia, 2001b; Pelfini and Gobbi, 2005; Pelfini and Smiraglia, 2007; Turchetti et al., 2008; Smiraglia et al., 2009) since the middle of the 19th century, thus representing a strong element of the mountain landscape and environment for people at local and national level (fig. 4).

Fig. 4 – A: Drawing of Forni Glacier reported in the book “Il Bel Paese” written by A. Stoppani and published in the year 1887.
Fig. 4 – A : Dessin du Glacier Forni extrait du livre d’A. Stoppani, « Il Bel Paese », publié en 1887.

Fig. 4 – A: Drawing of Forni Glacier reported in the book “Il Bel Paese” written by A. Stoppani and published in the year 1887.Fig. 4 – A : Dessin du Glacier Forni extrait du livre d’A. Stoppani, « Il Bel Paese », publié en 1887.

12The book represents the first attempt to describe by a unique author features and characteristics of the Italian country physical landscape. The drawing of the Forni Glacier was made some years before the book publication and it was probably made in 1836.

13Cet ouvrage constitue le premier essai de description par un même et unique auteur de la diversité des paysages naturels de l’Italie dans leurs différentes caractéristiques. Le dessin du glacier Forni a été exécuté plusieurs années avant la publication du livre, probablement en 1836.

Fig. 4 – B: Some tourists visiting Forni Glacier and walking at its surface at the end of the 19th century.
Fig. 4 – B : Quelques touristes visitant le glacier Forni à la fin du XIXe siècle et marchant à sa surface.

Fig. 4 – B: Some tourists visiting Forni Glacier and walking at its surface at the end of the 19th century.Fig. 4 – B : Quelques touristes visitant le glacier Forni à la fin du XIXe siècle et marchant à sa surface.

The Forni Glacier always represented a tourist attraction-pole and the homonymous hotel located at 2100 m a.s.l. was visited in summer by a large number of people since the end of the 19th century to enjoy the glacier-sight and the cooler climate.
Le glacier a toujours été un pôle d’attraction touristique, et depuis la fin du XIX
e siècle, l’hôtel du même nom situé à 2100 m d’altitude a régulièrement reçu, en été, la visite d’un grand nombre de personnes venues profiter de la vue des glaciers et du climat plus frais.

14More recently, the first supraglacial Automatic Weather Station (AWS) of the Italian Alps (Citterio et al., 2007b) was installed on its surface, thereby increasing the scientific value of the glacier. The AWS was already included in the international meteorological network SHARE (Stations at High Altitude for Research on the Environment) and in the CEOP network (Coordinated Energy and Water Cycle Observation Project), promoted by WCRP (World Climate Research Programme) within the framework of the GEWEX project (Global Energy and Water Cycle Experiment). The Forni Glacier is also included in the list of glaciers monitored by the Italian Glaciological Committee to evaluate changes in length (Comitato Glaciologico Italiano, 1914-1977, 1978-2008); moreover from historic maps and aerial photos, its area coverage has been calculated for the last 150 years. The results show that the Forni Glacier has experienced a marked decrease in length and area: from 17.80 km2 at the end of the LIA (~1860) to 11.62 km2 in 2003 (-34.7%). In the same time frame its tongue retreated by about 2 km (fig. 5 to fig. 7).

Fig. 5 – The recent (since the end of the Little Ice Age up to now) evolution of Forni Glacier.
Fig. 5 – L’évolution récente du glacier Forni (depuis la fin du Petit Âge Glaciaire jusqu’à nos jours)

Fig. 5 – The recent (since the end of the Little Ice Age up to now) evolution of Forni Glacier.Fig. 5 – L’évolution récente du glacier Forni (depuis la fin du Petit Âge Glaciaire jusqu’à nos jours)

A: 1890 (photo by V. Sella). B: 1941 (photo by A. Desio). C: 1997 (photo by C. Smiraglia). D: 2007 (photo by C. Smiraglia).
A: 1890 (photo V. Sella). B: 1941 (photo A. Desio). C: 1997 (photo C. Smiraglia). D: 2007 (photo C. Smiraglia).

Fig. 6 – The area coverage of Forni Glacier evaluated by analysing historic maps and moraine ridge position (1860 and 1952 data) and regional inventories (1991, 1999 and 2003 data).
Fig. 6 – La superficie du glacier Forni évalués à partir de l’analyse des cartes historiques et de la position des crêtes morainiques (données de 1860 et 1952), ainsi que des inventaires régionaux (données de 1991, 1999 et 2003).

Fig. 6 – The area coverage of Forni Glacier evaluated by analysing historic maps and moraine ridge position (1860 and 1952 data) and regional inventories (1991, 1999 and 2003 data). Fig. 6 – La superficie du glacier Forni évalués à partir de l’analyse des cartes historiques et de la position des crêtes morainiques (données de 1860 et 1952), ainsi que des inventaires régionaux (données de 1991, 1999 et 2003).

Fig. 7 – The terminus fluctuations of Forni Glacier measured from 1895 up to now
Fig. 7 – Les fluctuations de la langue terminale du glacier Forni de 1895 à nos jours

Fig. 7 – The terminus fluctuations of Forni Glacier measured from 1895 up to nowFig. 7 – Les fluctuations de la langue terminale du glacier Forni de 1895 à nos jours

(Italian Glaciological Committee’s data).
(données du Comité italien de glaciologie).

15Records for length variations in the Forni Glacier are among the longest standing in the Italian Alps, making Forni a benchmark glacier of primary importance. Fluctuation data for the glacier terminus show a basic retreating trend from 1895 to the present. A more detailed analysis of the front (fig. 7) reveals a more complex picture, showing a strong retreat from the end of the LIA up to the seventies, then a small advancing phase up to the second half of the eighties, when glacier decrease again became dominant. The retreat rates evaluated for recent decades (tab. 1) were higher than the ones calculated for the period 1895-1970. The Forni glacier was also the scene of an important event in Italian history during the First World War, when battles were fought on the glacier surface and on the mountain ridges overlooking the glacier valley. These events and the remaining evidence, now revealed by the large quantity of ruins and finds present at the glacier surface, add a cultural value to the glacier. For all of the above reasons the Forni glacier was included in the Lombardy Region official Geosite List (Regione Lombardia, 2009).

Tab. 1 – Forni Glacier length changes over the last century.
Tab. 1 – Les variations de longueur du glacier Forni au cours du siècle dernier.

Time frame

Total length variation (in m)

Annual change rate (in m/a)

1895-1970

- 1505

- 20.1

1971-1981

+ 303

+ 30.3

1982-2008

- 714.5

- 27.5

Recent changes in the Val Viola glacierised basin

16The Val Viola glacierised basin is a large area covering about 60 km2, all enclosed in the domain of the Municipality of Valdidentro (upper Valtellina, Lombardy) near the Italian-Swiss border. The area constitutes the SCI IT2040012 named “Val Viola Bormina - Ghiacciaio di Cima dei Piazzi” which is managed by the Sondrio Province Authority. Presently thirty glaciers are located in the Val Viola glacierised basin, covering altogether an area of approximately 4 km2, with different shapes, sizes and morphologies. The Val Viola area boasts a long series of investigations evaluating glacier terminus fluctuations, beginning in the first half of the 20th century (Comitato Glaciologico Italiano, 1914-1977, 1978-2008), mapping and dating the well preserved moraine ridges (Diolaiuti, 2002) and evaluating glacier mass balance, ice thicknesses and volume (by radio-echo-sounding surveys). More recently, the area was studied to investigate the glacier micro-meteorology (Diolaiuti et al., 2009b), assessing the effectiveness of artificial covering strategies aimed at reducing snow and ice ablation (Diolaiuti et al., 2009a), to develop methods of tourist promotion compatible with the level of biodiversity of the area (Diolaiuti et al., 2005) and to assess the impact of tourism on the physical landscape and ecological systems (Ferrarini et al., 2008). The comparison between the photographs shown in fig. 8 allows us to appreciate the marked retreat experienced by some glaciers in the Val Viola basin over the last seventy years.

Fig. 8 – A: Dosdè Glaciers, Viola Valley basin, summer 1932 (photo by Inventory of Italian Glaciological Committee). B: Dosdè Glaciers, Viola Valley basin, summer 2007 (photo by G. Diolaiuti).
Fig. 8 – A : Les glaciers Dosdè, bassin glaciaire du Val Viola, été 1932 (photo de l’inventaire du Comité italien de glaciologie). B : Les glaciers Dosdè, bassin glaciaire du Val Viola, été 2007 (photo G. Diolaiuti).

Fig. 8 – A: Dosdè Glaciers, Viola Valley basin, summer 1932 (photo by Inventory of Italian Glaciological Committee). B: Dosdè Glaciers, Viola Valley basin, summer 2007 (photo by G. Diolaiuti).Fig. 8 – A : Les glaciers Dosdè, bassin glaciaire du Val Viola, été 1932 (photo de l’inventaire du Comité italien de glaciologie). B : Les glaciers Dosdè, bassin glaciaire du Val Viola, été 2007 (photo G. Diolaiuti).

17The Val Viola glaciers have been subject to losses not only in volume and area (losing the largest part of their tongues) but have also seen an increase in their number. This numerical increase is a direct consequence of the ongoing deglaciation phase, which causes the fragmentation of previous larger glaciers and generating newly formed smaller ones. Further detail also enables in-depth analysis of length reduction in some selected glaciers located in the Val Viola basin. The Dosdè East Glacier, in particular, is the most studied glacier of the group (Diolaiuti, 2002; Diolaiuti et al., 2005); its tongue retreated by about 400 m over the last 50 years (about 30% of its total length in the second half of the 20th century). The terminus fluctuation trend (fig. 9) is more complex, showing a clear retreat from the fifties up to the seventies, then a small advancing phase in the second half of the eighties, followed again by glacier decrease. The trend is similar to that seen for the Forni Glacier terminus fluctuations, nevertheless the different magnitude is due to the Dosdè’s smaller size. The Dosdè retreat rates evaluated for recent decades (-24 m/a) proved higher than those calculated for the 1955-1970 period (-14 m/a). In order to evaluate glacier changes for the whole Val Viola glacierised basin over the last 50 years we analysed aerial photos dating from 1954 up to recent years. We compiled the 1954, 1981, 1999 and 2003 records by defining glacier outlines on aerial photographs (1954, 1981, 1999 and 2003 flights) and importing them to a GIS environment. The 1991 database, on the other hand, was compiled by previous authors (Servizio Glaciologico Lombardo, 1992).

Fig. 9 – The terminus fluctuations of Dosdè East Glacier measured from 1955 up to now (Italian Glaciological Committee’s data).
Fig. 9 – Les fluctuations de la langue terminale du glacier Dosdè Est, de 1955 à nos jours (données du Comité italien de glaciologie).

Fig. 9 – The terminus fluctuations of Dosdè East Glacier measured from 1955 up to now (Italian Glaciological Committee’s data). Fig. 9 – Les fluctuations de la langue terminale du glacier Dosdè Est, de 1955 à nos jours (données du Comité italien de glaciologie).

18The Val Viola glaciers we analysed are listed in tab. 2.

Tab. 2 – Surface area data of 28 glaciers located in the Val Viola Basin.
Tab. 2 – Surfaces des 28 glaciers situés dans le bassin du Val Viola.

Glacier name

aspect

Area 1954 (km2)

Area 1981 (km2)

Area 1991 (km2)

Area 1999 (km2)

Area 2003 (km2)

Corno Dosdè

N

0.05

0.02

0.02

0.01

0.01

Cima di Lago Spalmo Ovest

NW

0.10

0.08

0.05

0.05

0.03

Sasso Torto

NE

0.11

0.09

0.08

0.06

Passo Dosdè

W

0.13

0.10

0.05

Verva Minore

W

0.17

0.10

0.07

0.04

Verva Maggiore

NW

0.19

0.16

0.12

0.08

0.05

Redasco

N

0.20

0.13

0.06

0.01

Lago Calosso

NE

0.21

0.20

0.07

0.02

Campaccio

N

0.27

0.23

0.14

0.08

0.07

Rinalpi

N

0.28

0.22

0.16

0.10

0.08

Val Viola Est

NE

0.29

0.22

0.23

0.12

0.12

Passo dei Sassi Rossi Ovest

W

0.31

0.10

0.09

0.06

0.04

Lago Spalmo

S

0.40

0.25

0.24

0.15

0.13

Val Viola Ovest

N

0.42

0.30

0.18

0.14

0.12

Val Lia

N

0.75

0.66

0.56

0.52

0.46

Dosdè Ovest

NW

0.79

0.48

0.45

0.29

0.27

Dosdè Centrale I

N

0.89

0.76

0.28

0.67

0.21

Cardonnè

NW

1.06

1.02

1.04

0.92

0.85

Dosdè Est

NW

1.18

1.05

1.12

0.91

0.81

Cantone di Dosdè II

0.02

0.02

0.00

Cantone di Dosdè I

0.04

0.03

0.01

Dosdè Ovest Inferiore

0.02

Dosdè Centrale II

NW

0.47

0.34

Motti

E

(Glacieret) 0.16

(Glacieret) 0.13

San Colombano

N

(Glacieret) 0.18

(Glacieret) 0.04

Cima Dugorale

E

(Glacieret) 0.07

(Glacieret) 0.05

0.04

0.02

Sasso Campana

N

0.08

Dosdè Ovest II

0.01

total (km2)

8.21

6.53

5.55

4.1

3.77

total (km2) considering only glaciers marked with grey colour

7.74

6.18

5.51

3.77

Data were obtained by analysing aerial photos (1954 and 1983) and orthophotos (1999, 2003) and by previous regional glacier inventory (Servizio Glaciologico Lombardo, 1992). In the case no information about glacier area coverage are reported this could be due to the impossibility to detect the glacier in the aerial photos (cloud cover and/or snow coverage) or to the glacier disappearance. With grey colour were marked whose areas were evaluated and reported in four records (1954, 1981, 1991 and 2003) thus permitting the largest and more meaningful comparison. The surface decrease resulted to be stronger in the last period (1991-2003 time frame).
Les données ont été obtenues à partir de l’analyse des photos aériennes (1954, 1983) et des levés orthophotographiques (1999, 2003), ainsi que de la consultation de l’inventaire des glaciers régionaux publié en 1992 par le Service glaciologique de Lombardie. L’absence d’information sur la couverture glaciaire d’un secteur donné est à relier soit à l’impossibilité de détecter le glacier sur les photos aériennes (pour cause de couverture nuageuse et/ou de manteau neigeux), soit à la disparition du glacier lui-même. Les données marquées en gris correspondent aux secteurs ayant été évalués et décrits dans quatre rapports (1954, 1981, 1991 et 2003), qui permettent les comparaisons les meilleures et les plus signifiantes. C’est au cours de la dernière phase que la réduction de la superficie des glaciers semble être la plus forte (période 1991-2003).

19The Val Viola glacierized area was 8.21 km2 in 1954 (19 glaciers and 3 glacierets), 6.53 km2 in 1981 (22 glaciers and 3 glacierets), 5.55 km2 in 1991 (24 glaciers), 4.10 km2 in 1999 (14 glaciers) and 3.77 km2 in 2003 (23 glaciers). The number of glaciers surveyed is different in the four datasets due to the impossibility of detecting some glaciers in the aerial photos (cloud cover and/or snow coverage) or to glacier disappearance. So in order to evaluate the area changes we compared only the surface coverage of glaciers present in all the datasets (glaciers shown in grey in tab. 2). For this purpose we considered the 1954, 1981, 1991 and 2003 records, which enabled a comparison of the largest number of glaciers. The subset of glaciers analysed covered an area of 7.74 km2 in 1954, 6.18 km2 in 1981, 5.51 km2 in 1991 and 3.77 km2 in 2003. The area change between 2003 and 1954 was -3.97 km2 (-51% of the area coverage in 1954). Moreover, the surface reduction seems to be stronger in the last time frame; in fact, the area change in the period 1991-2003 (12 years) was -1.74 km2, as against an area change of -0.67 km2 in the period 1981-1991 (10 years) and an area variation of -1.57 km2 for the interval 1954-1981 (27 years). Furthermore, area changes in the Val Viola glaciers were analysed against total glacier areas (fig. 10), to investigate any relation between glacier reduction rate and glacier size. The results showed that the smaller the glacier the faster the reduction in size, reflecting findings by other authors for different Alpine glacierised sectors (Paul et al., 2004) and thus underlining how fast and unexpected glacier resources could disappear in cases where they are fragmented to a large number of small glaciers. All these studies underlined the scientific values of the Val Viola glacierised basin and the importance of its glaciers for the scientific community as witnesses of the ongoing climate change. The economic and cultural values of the valley also supported its inclusion in the Lombardy Region Geosite List (Regione Lombardia, 2009).

Fig. 10 – The area changes of Val Viola Glaciers.
Fig. 10 – Les changements de superficie des glaciers du Val Viola.

Fig. 10 – The area changes of Val Viola Glaciers.Fig. 10 – Les changements de superficie des glaciers du Val Viola.

On the y axis 1954-2003 area changes of Val Viola glaciers (% of area change with respect to the glacier area coverage in 1954), on the x axis area of Val Viola glaciers in 1954. It resulted the smaller glaciers to have experienced the stronger variations.
Sur l’axe y, évolution de la superficie des glaciers du Val Viola de 1954 à 2003 (en % du changement de la superficie par rapport à la surface englacée en 1954). Sur l’axe x, superficie des glaciers du Val Viola en 1954. Le graphique montre que les glaciers les plus petits ont connu les variations les plus fortes.

Phenomena following glacier recession and driving geo- and biodiversity

20As a consequence of glacier recession, increasingly larger valley areas are now abandoned by ice and new vegetation is starting to colonise the newly exposed rocks and mountain slopes, especially on the lower sectors of the deglaciated valleys (see the sequence of photos of the Forni Glacier in fig. 5 and the Val Viola basin in fig. 8). Another important landscape change is the increasing rock debris coverage. In fact, the Forni Glacier tongue, which has been always characterised only by two main medial moraines (both Ice Stream Interaction and Ablation Dominant types, see Smiraglia, 1989), now shows the increasing presence of supraglacial rock debris cover, ranging from quite continuous to sparse and sporadic; the surfaces of Val Viola glaciers also present increasing rock debris coverage (fig. 11). The rising rock debris coverage is mainly due to increased macrogelivation and rock degradation processes which seem more frequent and more pronounced in glacierised regions during recent years (O’Connor and Costa, 1993; Evans and Clague, 1994; Marchi and Tecca, 1996; Haeberli et al., 1997; Barla et al., 2000; Deline, 2005, 2009; Deline et al., 2004; Huggel et al., 2005; Chiarle et al., 2007; Gruber and Haeberli, 2007; Stokes et al., 2007; Deline and Kirkbride, 2008; Ravanel and Deline, 2008). In addition, glacier recession induced by climate warming causes an increase in supra-glacial slopes, enhancing the rate of paraglacially mobilised debris input, either from bedrock or pre-existing sediment storages on the glacier surface below. Consequently, the supra-glacial debris cover is prone to enlargement. Rates of debris input from the two adjacent supra-glacial slopes of a valley glacier may differ substantially from each other, reflecting different topography (varying debris entrainment and transport) and/or lithology (variations in weathering susceptibility) between the two sides. Moreover, the surface geometry of supra-glacial debris cover may be influenced by the spatial distribution and nature of medial moraines and/or of englacial debris septa, which melt out of the ice in the ablation area (Benn and Evans 1998; Anderson 2000; Kellerer-Pirklbauer et al., 2008). When glacier fronts become partially inactive, little shear fractures can channel the englacial sediments to the surface, covering the frontal part of the glacier surface with debris, some times forming shear moraines. The complexity of such phenomena explains the different debris cover distribution at the surface of the Forni Glacier and Val Viola Glaciers.

Fig. 11 – A: The Forni Glacier snout, rock debris is present ranging from a fine sparse layer (on the left in the photo) to a more continuous coverage which gives rise to differential ablation phenomena (the outstanding debris-covered ice, on the right in the photo).
Fig. 11 – A : La langue terminale du glacier Forni, sur laquelle les débris rocheux vont d’une fine couche de fragments clairsemés (sur la gauche sur la photo) à une couverture plus continue, donnant lieu à des phénomènes d’ablation différentielle (comme le montre la surface du glacier, sur la droite sur la photo).

Fig. 11 – A: The Forni Glacier snout, rock debris is present ranging from a fine sparse layer (on the left in the photo) to a more continuous coverage which gives rise to differential ablation phenomena (the outstanding debris-covered ice, on the right in the photo).Fig. 11 – A : La langue terminale du glacier Forni, sur laquelle les débris rocheux vont d’une fine couche de fragments clairsemés (sur la gauche sur la photo) à une couverture plus continue, donnant lieu à des phénomènes d’ablation différentielle (comme le montre la surface du glacier, sur la droite sur la photo).

21Moreover, supraglacial debris coverage plays a key role in determining rates and magnitudes of buried ice ablation (Østrem, 1959; Nakawo and Young, 1981, 1982; Nakawo and Takahashi, 1982; Nakawo and Rana, 1999). In fact, supraglacial debris cover, whenever thicker than the “critical value” (sensu Mattson and Gardner, 1989; Mattson et al., 1989, 1993), reduces magnitude and rates of glacier ice ablation (Mihalcea et al., 2006). Then the presence and the different distribution of supraglacial debris drive the genesis and the evolution of supraglacial morphologies due to differential ablation processes. On the Forni and the Val Viola glacier tongues (fig. 12), the most common and increasing epiglacial morphologies due to differential ablation are cryoconites, dirt cones and glacier tables (Smiraglia and Diolaiuti, in press). These morphologies are not exclusive to glacier recession but they are increasing in number and are becoming dominant in the epiglacial landscape due to the abundance of supraglacial debris following glacier shrinkage. In addition, differential ablation processes also produce strong gravitational and meltwater reworking of the former debris covered surface. The flanks of dirt cones and of medial moraines gradually become steeper, the abundance of debris and water produces debris flows and sliding - processes that redistribute sediments on the glacier surface, change the pattern of differential ablation and create in the deglaciation phases very characteristic and distinctive features.

Fig. 12 – A : Dirt cone on Forni glacier surface. B : Glacier table on Forni Glacier surface.
Fig. 12 – A : Cône de terre à cœur de glace à la surface du glacier Forni. B: Table glaciaire à la surface du glacier Forni.

Fig. 12 – A : Dirt cone on Forni glacier surface. B : Glacier table on Forni Glacier surface.Fig. 12 – A : Cône de terre à cœur de glace à la surface du glacier Forni. B: Table glaciaire à la surface du glacier Forni.

22The final phase of gravitational reworking is the development of a low-relief topography on the very thick debris mantle that considerably reduces ice ablation rates. On the lower central sector of the Forni glacier tongue, at present almost continuously covered in debris, the larger ice losses are mainly concentrated at the debris free areas such as the walls of open crevasses and other holes on the glacier surface and steep marginal areas. Ablation proceeds by the preferential melting and retreat of such slopes, in a process known as backwasting (Eyles, 1979). This process enlarges holes and produces a chain of a circular depression filled with water and favours the collapse of the roofs of englacial and subglacial water conduits (Kirkbride, 1993); the process results in a sequence of landscapes similar to the evolution of karst features on limestone terrain and is thus defined as glacier karst (Clayton, 1964). At the forefield of the Dosdè Central Glacier an interesting but vanishing morphology developed during the last 3 years revealing the ongoing phase of glacier shrinkage: an ice cave (fig. 13). The ice cave developed from an abandoned sector of the glacier tongue. The dead ice was covered by a thick debris layer which reduced ice ablation thus permitting it to survive. The ice cave (ca. 500 m2 of area) was firstly shaped by a glacier meltwater stream, then when the debris covered glacier sector was abandoned by the glacier main body it remained open thus allowing observation of the area at the contact with the glacier bedrock. This morphology constituted an attractive feature for tourists and climbers thus contributing to increasing the popularity of the Val Viola basin. All of these features - increasing in number on the Forni Glacier tongue and on the Val Viola glacier surface due to rising supraglacial debris coverage - are temporarily increasing local geodiversity. In addition, the spread of glacial debris coverage is determining an increase in the typical habitat of several vegetal species (herbaceous and shrubby), thus promoting the migration of lithophyte and microthermal species toward higher altitude and a consequent increase in local biodiversity (Körner, 1999).

Fig. 13 – The ice cave developed at forefield of Dosdè Centrale Glacier from a relict sector of the glacier tongue.
Fig. 13 – La grotte de glace apparue sur la marge proglaciaire du glacier Dosdè Central, au niveau d’une partie résiduelle de la langue terminale.

Fig. 13 – The ice cave developed at forefield of Dosdè Centrale Glacier from a relict sector of the glacier tongue. Fig. 13 – La grotte de glace apparue sur la marge proglaciaire du glacier Dosdè Central, au niveau d’une partie résiduelle de la langue terminale.

The debris-covered ice constituting the cave permitted it to survive and to be appreciable over the last three years. It became an attraction for tourists and climbers (photo by A. Greco).
Les débris qui recouvrent la glace constituant la grotte lui ont permis de subsister et de conserver un volume non négligeable au cours des trois dernières années. Elle est ainsi devenue une attraction pour les randonneurs et les alpinistes (photo A. Greco).

23Other morphologies increasingly seen due to glacier shrinkage are rounded rock outcrops and small nunataks outstanding from glacier surfaces or enlarging their size at the glacier boundary. They are characterised by fast evolution and in the space of a few years they can cause glacier fragmentation. On the Forni Glacier, several outcrops are evident on ice seracs connecting the three upper accumulation basins with the main ablation tongue. Here the steepness of the rock slopes drives ice-flow, thereby reducing ice thickness and shaping the flows as actual ice falls. In particular, on the east ice fall an outcrop has been developing over the last three years. This outcrop is causing a separation between the upper east accumulation basin and the main glacier tongue (fig. 14). The eventual result of this evolution will be the transformation of the east accumulation basin into an isolated cirque glacier. Another result of outcrop development is the fragmentation of the Dosdè Central Glacier (Val Viola basin) which, between 1933 and 2007, from a single glacier body (fig. 8A), was divided into two separate glaciers (fig. 8B).

Fig. 14 – The outcrop driving the separation between the Forni upper east accumulation basin and the main glacier tongue.
Fig. 14 – L’affleurement rocheux séparant le bassin d’accumulation supérieur du glacier Forni oriental de la langue du glacier principal.

Fig. 14 – The outcrop driving the separation between the Forni upper east accumulation basin and the main glacier tongue.Fig. 14 – L’affleurement rocheux séparant le bassin d’accumulation supérieur du glacier Forni oriental de la langue du glacier principal.

24Glacier melting also leads to the formation of glacial lakes. The newly formed lakes are located at the glacier surface, at the glacier boundary (lateral and frontal position) and in the glacier forefield. The lakes located at the Forni Glacier surface are actually large water ponds which act as heat-storage, thus increasing surface melting and accelerating glacier recession. Their evolution is fast and generally their lifespan is shorter than one year. The lakes located at the glacier boundary are the ice–contact type (fig. 15). These are becoming increasingly widespread morphologies, not only at the Forni Glacier boundary but also at the contact of several Alpine glaciers due to the current phase of glacier shrinkage. In fact, the retreat of glacier termini has produced favourable settings for ponding of small ice-contact lakes behind moraine ridges, particularly those formed by the most recent glacier advance in the late 20th century, or in less frequent cases (e.g., the Forni Glacier), the lake-dam is formed by glacier ice. The ice-contact conditions allow calving phenomena to occur, driving generation of icebergs. At the Forni Glacier calving events are limited and they occur on a smaller scale compared with glacier calving found at higher latitudes, nevertheless the phenomenon exists and is appreciable. The lifespan of ice-water contact at alpine glaciers is, however, generally limited. Either most of the newly formed lakes disappear after a few years, or the accelerating retreat of the glacier snouts implies a rapid evolution from ice-contact to distal proglacial lakes (Masetti et al., 2009). The persistence in time and space of such conditions seems to be longer where the glacier surface in the ice-contact zone is covered by debris that reduces ablation (i.e., a debris thickness thicker than the critical value) because of the greater stability of the ice margin.

Fig. 15 – A: Ice contact lake at the lateral side of Forni Glacier in 2006 when its genesis started. B: Ice contact lake at the lateral side of Forni Glacier in 2007, it is appreciable the debris-covered glacier ice constituting the lake dam.
Fig. 15 – A : Lac juxtaglaciaire au début de sa formation sur l’une des marges du glacier Forni en 2006. B : Lac juxtaglaciaire sur l’une des marges du glacier Forni en 2007, avec vue sur la glace couverte de débris formant barrage.

Fig. 15 – A: Ice contact lake at the lateral side of Forni Glacier in 2006 when its genesis started. B: Ice contact lake at the lateral side of Forni Glacier in 2007, it is appreciable the debris-covered glacier ice constituting the lake dam.Fig. 15 – A : Lac juxtaglaciaire au début de sa formation sur l’une des marges du glacier Forni en 2006. B : Lac juxtaglaciaire sur l’une des marges du glacier Forni en 2007, avec vue sur la glace couverte de débris formant barrage.

The ice-core of the lateral moraine is visible as well.
Le noyau de glace de la moraine latérale est également bien visible.

25The existence of ice contact lakes allows water to be stored at higher elevations, even if for short and temporary periods, giving rise to local ecosystems where yeasts and bacteria which have adapted to extreme environments are able to survive (Buzzini et al., 2005), thus increasing biodiversity at a local level. The Forni Glacier ice contact lake is now experiencing a growing phase and during the last 4 years it passed from being a simple small water pond, to its present maximum length exceeding 150 m. Furthermore, lateral moraines too are experiencing deep changes due to ongoing climate change. This is the case of the lateral moraines of the Forni Glacier, affected by ice core melting with subsequent collapse and genesis of mud and debris flows. The moraine ridges providing evidence of such events were deposited by the glacier during the last advancing phase (seventies-eighties of the 20th century, see fig. 7 and fig. 15B, in the latter the ice core is visible). In fact, starting from the nineties, several phenomena of fast slope evolution, due to ice core melting, occurred (mainly mud and debris flow events), causing radical changes in moraine morphology and prompting a modification of the tourist-trail enabling access to the glacier snout (Smiraglia et al., 2009).

26Given the scenarios described above, the present ablation tongue of the Forni Glacier and Val Viola basin glaciers, together with their glacier forefields, could represent a unique new geomorphosite or a “complex integrated system of geomorphosites” experiencing a rapid evolution, where it is possible to observe all the different transition phases from glacial environments to deglaciated ones. The consequences of this rapid evolution for geosite assessment, management, conservation and valorisation are important and demand urgent strategies to manage such zones, which represent a unique tool for raising public awareness of climate change impact. On the other hand such territories are fragile due to the rapid variations they are undergoing, requiring guided visits to prevent accelerated degradation of morphological evidence.

Discussion and conclusions

27Our data show that the trend of terminus fluctuations in the Forni and Dosdè East Glacier reflects the general pattern for glaciers all over the Alps, i.e. in retreat from the end of the LIA up to the present (Zemp et al., 2006), with a short interruption during the 1970’s and the 1980’s (Patzelt, 1985; Wood, 1988). In addition, the analysis of regional glacier inventories we performed together with the studies carried out at a local scale (i.e., on the Forni Glacier and Val Viola Basin) reveals a more pronounced reduction in glacier coverage over the last decade. The glacial reduction demonstrated by these findings is interpreted as a real impact of climate change. Indeed, as the transfer function between climate changes and glacier variations does not change in time (Oerlemans, 2005), an acceleration in glacial changes is suggested. Extrapolations of developments documented by repeated glacier inventories (Kaab et al., 2002; Paul et al., 2004) and provided by numerical models (Oerlemans et al., 1998) both suggest that the disappearance of many mountain glaciers is quite likely to be a matter of few decades (Haeberli, 2008). The Forni Glacier and Val Viola basin glaciers could also be victims of this ominous scenario if no meaningful changes occur in the climate warming trend. The Forni Glacier will firstly be split into three smaller glaciers due to fragmentation of the present glacier body, then the newly formed cirque glaciers will dwindle and will have completely vanished by the end of this century. In the case of the Val Viola basin, the glacier decline and disappearance will be faster and may occur and be completed within the next two decades. These ongoing shrinkage phenomena are changing in a radical way the mountain landscape of the Lombardy Alps. It is expected they will initially present features and forms now found in the Pyrenees (where current glaciation is the remains of the more widespread previous situation and is formed by small cirque glaciers and snow patches, see González Trueba et al., 2008) and, in a second phase to resemble the Apennines (where only the Calderone Glacier can be found, now classified as a “debris covered glacieret”together with small snow-patches). Furthermore, the retreat and extinction of mountain glaciers and the disappearance of the geomorphosites linked to their presence are occurring together with the genesis of new, smaller geomorphosites, which in turn trigger a new complex landscape system. The morphologies described above, found at the surface and at the boundary of the Forni and Val Viola glaciers, are good examples of such phenomenon. From a geodynamical point of view, the transition is now taking place from a glacial system to a paraglacial one (sensu Ballantyne and Benn, 1994, 1996; Curry and Ballantyne, 1999). Areas where in the recent past the main shaping and driving factors were glaciers are now subject to the action of melting water, slope evolution and dynamics and periglacial processes. The next step will be the transition from a paraglacial environment, where ice-patches or glacierets are presents, to a periglacial environment where cold and snow are dominant, without ice glaciers or ice melt water.

28The scientific value of the newly formed morphologies - as witnesses of ongoing deglaciation and climate change - together with their scenic and aesthetic values, suggest they should be considered as independent geomorphosites. This is particularly true considering the changes affecting the Forni Glacier, where the present retreat of the glacier snout is generating an ice-free, wide and quite flat area which promotes deposition processes and building of fresh morphologies. The Forni glacier forefield is therefore becoming an “open air environmental museum of deglaciation” where people can see the effect of climate change on a glacier system and on mountain landscapes, even in short time frames. Furthermore, when the Forni Glacier and the Val Viola glaciers have completely disappeared, a major visible impact will occur in the aesthetic value of the mountains. Ice melting will turn the snow-covered mountains into bare, rocky mountains. The dynamic glaciers will turn into lifeless rubble without their icy core. And in addition to these changes impacting on tourism and culture, the lack of snow and ice will also have consequences on the climbing experience. Some scientists show optimistic prospects based on the possibility that vegetation and plants will rapidly colonise the deglaciated areas. This is an ongoing process on the upper deglaciated sectors (see our photo comparisons in fig. 5 and fig. 8) but such processes requires longer time frames for completion and it is unlikely that the deglaciated Alps will rapidly become a green landscape with an open (and cultivated) forest/meadow pattern surrounding some pretty remains of surface snow without any visible debris or moraines (Haeberli, 2008). In reality, several authors and our findings suggest the developments of the next decades will include the complete disappearance of small mountain glaciers and down wasting, rather than retreat for long valley glaciers (Haeberli, 2008). This already discernable trend may be accompanied by the development of extreme and long-lasting disequilibria in the abiotic as well as the biotic parts of ecosystems and habitats, not only in high mountain areas but elsewhere (Watson and Haeberli, 2004). In this context attention must be paid to the question of conservation.

29From a general point of view, conservation of natural heritage is the management of change, and climate change is one of the most significant global challenges facing the environment and the natural heritage today (UNESCO-World Heritage Center, 2007b). The action needed to safeguard glacier heritage includes:

30i) Preventive action; monitoring, reporting and mitigation of climate change effects at a range of levels (individual, community, institutional and corporate). In particular, regarding mitigation strategies some attempts have been made to reduce ice and snow melting by applying artificial coverage (preventive action, see Olefs and Fisher, 2008, and on the Val Viola Basin, Diolaiuti et al., 2009a), nevertheless such efforts could not be applied to large glacierised areas and could not change the ongoing decreasing trend.

31ii) Corrective action; adaptation to the reality of climate change through global and regional strategies and local management plans. In this field the greatest efforts made include adaptation of tourist glacier trails (e.g., Forni Glacier tourist trail in Smiraglia et al., 2009, Val Viola basin tourist paths in Ferrarini et al., 2008) and changing meltwater use and management according to the changed and changing meltwater availability.

32iii) Sharing knowledge; including best practices, research, communication, public and political support, education and training, capacity building, networking, etc. In this field a lot could be done to increase awareness of climate change and human responsibilities, and to prepare people for the eventuality of a possible future alpine landscape without glaciers (cultural adaptation strategies). Then our once beautiful glacierised mountains, such as the Forni Valley and Val Viola Basin, are now deeply changing, becoming key witnesses to the general and serious impact humans have wrought on the Planet (Watson and Haeberli, 2004). In this sense glacier monitoring programmes are becoming activities of ever increasing socio-economic and political importance (Haeberli, 2008) and projects for promotion and conservation of glacier geosites may give people the chance to raise their awareness of global environmental change. Moreover the managers of the glacier geosites (parks, local and/or national governments, etc.) must integrate climate change issues into management plans including risk preparedness, adaptive design and management planning.

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Annexe

Version française abrégée

Nombre d’éléments remarquables du patrimoine géologique et géomorphologique courent le risque de subir les effets du changement climatique global, en particulier les glaciers de montagne et leurs abords. Parce que les glaciers de montagne sont aujourd’hui en recul dans le monde entier, certains géosites montagnards inscrits sur des listes nationales et/ou internationales (comme la Liste du Patrimoine mondial de l’UNESCO) verront sans doute leur aspect profondément changer à brève échéance.

Les conséquences de la fonte des glaciers alpins sur le patrimoine naturel et culturel n’ont pas encore été étudiées en détail et seules des études préliminaires ont été réalisées jusqu’à présent (UNESCO-Centre du patrimoine mondial, 2007a ; Haeberli, 2008). On résume ici l’évolution des glaciers alpins en indiquant quelles conséquences directes et indirectes les tendances actuelles entraînent sur les caractéristiques et les valeurs des géosites. L’étude prend comme exemple deux domaines clés des Alpes italiennes : le glacier Forni et le Val Viola, inscrits comme géomorphosites sur la liste officielle de l’Inventaire des géosites de la province de Sondrio (Regione Lombardia, 2009). Les sites analysés sont parmi les plus grands glaciers de vallée des Alpes italiennes : le glacier Forni occupe 12 km2 dans le massif Ortles-Cevedale tandis que le bassin glaciaire du Val Viola montre différents petits glaciers et plusieurs crêtes morainiques bien conservées datant de l’Holocène supérieur à l’Actuel. Les géosites Forni et Val Viola sont situés dans des territoires définis comme « sites d’importance communautaire » (SIC) selon la directive 92/43/CEE, le glacier Forni étant inclus dans le Parc national du Stelvio, l’un des principaux espaces protégés d’Italie. Depuis le milieu du XIXe siècle, le glacier Forni a été visité pour des raisons scientifiques et à des fins touristiques (Stoppani, 1908 ; Smiraglia, 1984 a et b, 1988, 1989 ; Guglielmin et al., 1995 ; Diolaiuti et Smiraglia, 2001b ; Pelfini et Gobbi, 2005 ; Pelfini et Smiraglia, 2007 ; Turchetti et al., 2008 ; Smiraglia et al., 2009), ce qui montre à quel point cette unité de relief constitue pour tous un important élément du paysage et du milieu montagnard, tant au niveau local que national. Plus récemment, la première station météorologique automatique supra-glaciaire des Alpes italiennes a été installée à la surface du glacier Forni (Citterio et al., 2007b), renforçant ainsi sa valeur scientifique. Cet appareil glaciaire fait aussi partie des objets surveillés par le Comité italien de glaciologie pour évaluer les changements de longueur des glaciers (Comitato Glaciologico Italiano, 1914-1977, 1978-2008). L’ensemble des résultats montre que le glacier Forni a connu un recul marqué de sa longueur et une diminution non moins remarquable de sa surface, passée de 17,8 km2 à la fin du Petit Age Glacaire (~ 1860), à 11,62 km2 en 2003 (-34,7 %). Le glacier Forni a aussi été le témoin des événements historiques ayant affecté l’Italie au cours de la Première Guerre mondiale. Les nombreuses ruines présentes témoignent de l’âpreté des combats survenus à la surface du glacier et sur les crêtes environnantes, ces vestiges conférant à la vallée glaciaire une valeur culturelle additionnelle en terme de géomorphosite. Pour ce qui concerne le bassin glaciaire du Val Viola, ce vaste espace d’environ 60 km2 est intégralement situé dans la commune de Valdidentro en haute Valtelline (Lombardie), près de la frontière italo-suisse. Actuellement, trente glaciers se répartissent dans l’ensemble du domaine glaciaire du Val Viola, pour une surface cumulée de l’ordre de 4 km2, avec des apparences, des dimensions et des formes du relief différentes. Le secteur du Val Viola bénéficie d’une longue série d’enquêtes ayant débuté pendant la première moitié du XXe siècle (Comitato Glaciologico Italiano, 1914-1977, 1978-2008). Ces observations ont permis d’évaluer les fluctuations de la langue terminale, à partir de la cartographie et de la datation des crêtes morainiques bien conservées d’une part (Diolaiuti, 2002), du bilan de masse des glaciers d’autre part. Plus récemment, le domaine du Val Viola a fait l’objet d’enquêtes destinées, les unes à étudier la micro-météorologie glaciaire dans le but d’évaluer l’efficacité des stratégies de couverture artificielle visant à réduire la fonte de la couverture neigeuse et l’ablation de la glace (Diolaiuti et al., 2009 a et b), les autres à développer des méthodes de promotion du tourisme compatibles avec le niveau de biodiversité de la zone (Diolaiuti et al., 2005) et permettant d’évaluer l’impact du tourisme tant sur les composantes biotiques et abiotiques du paysage que sur les systèmes écologiques associés (Ferrarini et al., 2008).

Afin d’estimer les modifications des glaciers de l’ensemble du bassin glaciaire du Val Viola au cours du dernier demi-siècle, nous avons analysé des photos aériennes datant de 1954 à 2003. Entre ces deux dates, la diminution de la superficie des glaciers a été de 3,97 km2 (soit 51 % de l’aire englacée en 1954), le phénomène semblant s’accélérer au cours de la dernière période de l’intervalle considéré. En outre, les changements survenus dans le bassin glaciaire du Val Viola ont été confrontés aux résultats obtenus pour l’ensemble des régions englacées, afin de déceler toute relation pouvant exister entre recul et taille des glaciers. Les résultats ont montré que plus le glacier est petit, plus rapide est son recul, ce qui rejoint les conclusions d’autres auteurs pour différents secteurs englacés des Alpes (Paul et al., 2004). On met ainsi en lumière le fait que des appareils glaciaires pourraient disparaître de façon rapide et inattendue dans le cas où la ressource est fragmentée en un grand nombre de petits glaciers. Toutes ces études soulignent l’intérêt du bassin glaciaire du Val Viola et l’importance de ses petits glaciers pour la communauté scientifique en tant que témoins du changement climatique en cours.

En conséquence du recul des glaciers, des surfaces de plus en plus grandes de la vallée sont aujourd’hui libres de glace, une jeune végétation commençant à coloniser les versants montagnards et les affleurements rocheux nouvellement exposés, en particulier dans le bas des vallées déglacées. Une autre modification importante du paysage est l’accroissement de la couverture de débris rocheux dans le relief. Ainsi, la langue du glacier Forni, qui a toujours été caractérisée par seulement deux moraines médianes principales, tend à être recouverte par une masse croissante de débris rocheux supraglaciaires, des observations similaires pouvant être effectuées dans le Val Viola. Ceci est d’autant plus important que la couverture de débris supraglaciaires joue un rôle essentiel dans la détermination des taux et de l’ampleur de l’ablation de la glace enterrée (Østrem, 1959 ; Nakawo et Young, 1981, 1982 ; Nakawo et Takahashi, 1982 ; Nakawo et Rana, 1999).

Par leur localisation et leur répartition, les débris rocheux éclairent ainsi la genèse et l’évolution des morphologies supraglaciaires liées aux processus d’ablation différentielle. Sur la langue du glacier Forni et à la surface des appareils du Val Viola, les formes épiglaciaires d’ablation différentielle les plus courantes sont les trous de cryoconites, les cônes de terre à cœur de glace (dirt cones) et les tables de glaciers (Smiraglia et Diolaiuti, sous presse). Ces formes tendent à se multiplier du fait de l’accroissement du volume des débris supraglaciaires, avec comme résultat à la fois une augmentation temporaire de la géodiversité locale et un essor de l’habitat type de plusieurs espèces végétales (herbacées et arbustives), essor qui favorise à son tour la migration des lithophytes et autres espèces microthermes vers des altitudes plus élevées, d’où une augmentation non négligeable de la biodiversité locale (Körner, 1999).

D’autres formes de plus en plus fréquemment observées du fait du recul des glaciers sont les affleurement de roches moutonnées, ainsi que des nunataks de faible volume dépassant tout juste de la surface des glaciers, ou de plus fort volume à la limite de ces derniers. La fonte des glaciers entraîne aussi la formation de lacs glaciaires. Les lacs nouvellement formés s’observent à la surface ou à la limite du glacier, en position latérale ou frontale, ainsi qu’en avant du glacier lui-même. L’évolution de ces lacs est rapide et leur durée de vie est en général inférieure à un an. L’existence de lacs au contact de la glace permet à l’eau d’être stockée à l’état liquide à des altitudes plus élevées, même si ce n’est que pour des périodes courtes et temporaires. Mais ceci explique l’apparition d’écosystèmes où des levures et des bactéries qui se sont adaptées à des environnements extrêmes sont capables de survivre (Buzzini et al., 2005), ce qui joue encore dans le sens d’une augmentation de la biodiversité locale.

Compte tenu des scénarios décrits ci-dessus, l’actuelle langue d’ablation du glacier Forni et les petits glaciers du Val Viola avec leurs marges proglaciaires pourraient représenter soit un unique et nouveau grand géomorphosite, soit un « système intégré complexe de petits géomorphosites ». Au sein de cet ensemble en rapide transformation, il est possible d’observer tous les intermédiaires entre un environnement glaciaire et un milieu libre de glace. Les conséquences de cette rapidité sur l’évaluation, la gestion, la conservation et la valorisation des géomorphosites sont importantes ; la gestion de tels espaces nécessite de façon urgente la mise au point de stratégies nouvelles, car ils constituent un outil unique et exceptionnel pour qui cherche à éveiller le public aux effets du changement climatique. D’autre part, de tels territoires sont fragiles en raison de la rapidité même des variations qu’ils subissent, ce qui nécessite l’organisation de visites guidées si l’on veut éviter la dégradation accélérée des preuves géomorphologiques du changement climatique.

En outre, lorsque le glacier Forni et les glaciers du Val Viola auront entièrement disparu, la valeur esthétique des montagne environnantes sera durablement altérée. La fonte des glaces transformera des montagnes couvertes de neiges éternelles en montagnes rocheuses et dénudées. Une fois leur cœur stoppé, les glaciers mouvants se transformeront en ruines inanimées. Et en plus de ces changements affectant le tourisme et la culture, le manque de neige et de glace aura également des conséquences sur la pratique de l’escalade. Ainsi nos belles montagnes englacées que sont la vallée de Forni et le bassin du Val Viola sont-elles en train de changer profondément, témoignant à leur façon mais de manière cruciale des profonds et universels bouleversements que les sociétés infligent à la planète (Watson et Haeberli, 2004). Les gestionnaires des géosites glaciaires (parcs naturels, autorités locales et/ou gouvernements nationaux, etc.) doivent intégrer les questions liées au changement climatique dans les plans de gestion, y compris la préparation aux risques et la conception de politiques de gestion adaptatives.

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Table des illustrations

Titre Fig. 1 – Simplified sketch showing the flow of effects deriving from climate change (main driving factor), to glacier change (driving factor dependent from climate) to the main elements of mountain environment. Fig. 1 – Schéma simplifié montrant le lien entre le changement climatique global (facteur causal principal) et ses effets sur les principaux éléments du milieu montagnard, par l’intermédiaire des transformations des glaciers (facteur causal second, dérivé du changement climatique).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-1.png
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Titre Fig. 2 – The Forni Glacier (Ortles-Cevedale group, Central Italian Alps).Fig. 2 – Le glacier Forni (massif d’Ortles-Cevedale, Alpes centrales italiennes).
Légende A: Map of the Forni Glacier. The black dot indicates the supraglacial Automatic Weather Station (AWS); 1: supraglacial debris; 2: rock nunataks. B: Photo of the Forni Glacier. The photo was taken by G. Diolaiuti from the summit of Mount San Matteo (3670 m, the white triangle in the map).A : Carte du glacier Forni. Le point noir indique l’emplacement de la station météorologique supraglaciaire automatique (AWS) ; 1 : débris supraglaciaires ; 2 : pointements rocheux (nunataks). B : Photo du glacier Forni, prise par G. Diolaiuti depuis le sommet du Mont San Matteo (3670 m, le triangle blanc sur la carte).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-2.jpg
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Titre Fig. 3 – The Val Viola glaciarised basin (Piazzi-Campo group; Central Italian Alps).Fig. 3 – Le bassin glaciaire du Val Viola (massif Piazzi-Campo, Alpes centrales italiennes).
Légende A: Map of the Val Viola glaciarised basin; 1: 1981 glacier area; 2: 2003 glacier area. B. Photo of the Val Viola glaciarised basin (photo by G. Diolaiuti).A : Carte du bassin glaciaire du Val Viola ; 1 : extension des glaciers en 1981 ; 2 : domaine englacé en 2003. B : Photo du bassin glaciaire du Val Viola, par G. Diolaiuti.
URL http://geomorphologie.revues.org/docannexe/image/7882/img-3.jpg
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Titre Fig. 4 – A: Drawing of Forni Glacier reported in the book “Il Bel Paese” written by A. Stoppani and published in the year 1887.Fig. 4 – A : Dessin du Glacier Forni extrait du livre d’A. Stoppani, « Il Bel Paese », publié en 1887.
URL http://geomorphologie.revues.org/docannexe/image/7882/img-4.jpg
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Titre Fig. 4 – B: Some tourists visiting Forni Glacier and walking at its surface at the end of the 19th century.Fig. 4 – B : Quelques touristes visitant le glacier Forni à la fin du XIXe siècle et marchant à sa surface.
Légende The Forni Glacier always represented a tourist attraction-pole and the homonymous hotel located at 2100 m a.s.l. was visited in summer by a large number of people since the end of the 19th century to enjoy the glacier-sight and the cooler climate. Le glacier a toujours été un pôle d’attraction touristique, et depuis la fin du XIXe siècle, l’hôtel du même nom situé à 2100 m d’altitude a régulièrement reçu, en été, la visite d’un grand nombre de personnes venues profiter de la vue des glaciers et du climat plus frais.
URL http://geomorphologie.revues.org/docannexe/image/7882/img-5.png
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Titre Fig. 5 – The recent (since the end of the Little Ice Age up to now) evolution of Forni Glacier.Fig. 5 – L’évolution récente du glacier Forni (depuis la fin du Petit Âge Glaciaire jusqu’à nos jours)
Crédits A: 1890 (photo by V. Sella). B: 1941 (photo by A. Desio). C: 1997 (photo by C. Smiraglia). D: 2007 (photo by C. Smiraglia).A: 1890 (photo V. Sella). B: 1941 (photo A. Desio). C: 1997 (photo C. Smiraglia). D: 2007 (photo C. Smiraglia).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-6.jpg
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Titre Fig. 6 – The area coverage of Forni Glacier evaluated by analysing historic maps and moraine ridge position (1860 and 1952 data) and regional inventories (1991, 1999 and 2003 data). Fig. 6 – La superficie du glacier Forni évalués à partir de l’analyse des cartes historiques et de la position des crêtes morainiques (données de 1860 et 1952), ainsi que des inventaires régionaux (données de 1991, 1999 et 2003).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-7.png
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Titre Fig. 7 – The terminus fluctuations of Forni Glacier measured from 1895 up to nowFig. 7 – Les fluctuations de la langue terminale du glacier Forni de 1895 à nos jours
Crédits (Italian Glaciological Committee’s data). (données du Comité italien de glaciologie).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-8.png
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Titre Fig. 8 – A: Dosdè Glaciers, Viola Valley basin, summer 1932 (photo by Inventory of Italian Glaciological Committee). B: Dosdè Glaciers, Viola Valley basin, summer 2007 (photo by G. Diolaiuti).Fig. 8 – A : Les glaciers Dosdè, bassin glaciaire du Val Viola, été 1932 (photo de l’inventaire du Comité italien de glaciologie). B : Les glaciers Dosdè, bassin glaciaire du Val Viola, été 2007 (photo G. Diolaiuti).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-9.jpg
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Titre Fig. 9 – The terminus fluctuations of Dosdè East Glacier measured from 1955 up to now (Italian Glaciological Committee’s data). Fig. 9 – Les fluctuations de la langue terminale du glacier Dosdè Est, de 1955 à nos jours (données du Comité italien de glaciologie).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-10.png
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Titre Fig. 10 – The area changes of Val Viola Glaciers.Fig. 10 – Les changements de superficie des glaciers du Val Viola.
Légende On the y axis 1954-2003 area changes of Val Viola glaciers (% of area change with respect to the glacier area coverage in 1954), on the x axis area of Val Viola glaciers in 1954. It resulted the smaller glaciers to have experienced the stronger variations.Sur l’axe y, évolution de la superficie des glaciers du Val Viola de 1954 à 2003 (en % du changement de la superficie par rapport à la surface englacée en 1954). Sur l’axe x, superficie des glaciers du Val Viola en 1954. Le graphique montre que les glaciers les plus petits ont connu les variations les plus fortes.
URL http://geomorphologie.revues.org/docannexe/image/7882/img-11.jpg
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Titre Fig. 11 – A: The Forni Glacier snout, rock debris is present ranging from a fine sparse layer (on the left in the photo) to a more continuous coverage which gives rise to differential ablation phenomena (the outstanding debris-covered ice, on the right in the photo).Fig. 11 – A : La langue terminale du glacier Forni, sur laquelle les débris rocheux vont d’une fine couche de fragments clairsemés (sur la gauche sur la photo) à une couverture plus continue, donnant lieu à des phénomènes d’ablation différentielle (comme le montre la surface du glacier, sur la droite sur la photo).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-12.jpg
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Titre Fig. 12 – A : Dirt cone on Forni glacier surface. B : Glacier table on Forni Glacier surface.Fig. 12 – A : Cône de terre à cœur de glace à la surface du glacier Forni. B: Table glaciaire à la surface du glacier Forni.
URL http://geomorphologie.revues.org/docannexe/image/7882/img-13.jpg
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Titre Fig. 13 – The ice cave developed at forefield of Dosdè Centrale Glacier from a relict sector of the glacier tongue. Fig. 13 – La grotte de glace apparue sur la marge proglaciaire du glacier Dosdè Central, au niveau d’une partie résiduelle de la langue terminale.
Légende The debris-covered ice constituting the cave permitted it to survive and to be appreciable over the last three years. It became an attraction for tourists and climbers (photo by A. Greco).Les débris qui recouvrent la glace constituant la grotte lui ont permis de subsister et de conserver un volume non négligeable au cours des trois dernières années. Elle est ainsi devenue une attraction pour les randonneurs et les alpinistes (photo A. Greco).
URL http://geomorphologie.revues.org/docannexe/image/7882/img-14.jpg
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Titre Fig. 14 – The outcrop driving the separation between the Forni upper east accumulation basin and the main glacier tongue.Fig. 14 – L’affleurement rocheux séparant le bassin d’accumulation supérieur du glacier Forni oriental de la langue du glacier principal.
URL http://geomorphologie.revues.org/docannexe/image/7882/img-15.jpg
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Titre Fig. 15 – A: Ice contact lake at the lateral side of Forni Glacier in 2006 when its genesis started. B: Ice contact lake at the lateral side of Forni Glacier in 2007, it is appreciable the debris-covered glacier ice constituting the lake dam.Fig. 15 – A : Lac juxtaglaciaire au début de sa formation sur l’une des marges du glacier Forni en 2006. B : Lac juxtaglaciaire sur l’une des marges du glacier Forni en 2007, avec vue sur la glace couverte de débris formant barrage.
Légende The ice-core of the lateral moraine is visible as well.Le noyau de glace de la moraine latérale est également bien visible.
URL http://geomorphologie.revues.org/docannexe/image/7882/img-16.jpg
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Pour citer cet article

Référence papier

Guglielmina Diolaiuti et Claudio Smiraglia, « Changing glaciers in a changing climate: how vanishing geomorphosites have been driving deep changes in mountain landscapes and environments », Géomorphologie : relief, processus, environnement, vol. 16 - n° 2 | 2010, 131-152.

Référence électronique

Guglielmina Diolaiuti et Claudio Smiraglia, « Changing glaciers in a changing climate: how vanishing geomorphosites have been driving deep changes in mountain landscapes and environments », Géomorphologie : relief, processus, environnement [En ligne], vol. 16 - n° 2 | 2010, mis en ligne le 01 juillet 2012, consulté le 22 novembre 2017. URL : http://geomorphologie.revues.org/7882 ; DOI : 10.4000/geomorphologie.7882

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Auteurs

Guglielmina Diolaiuti

Dipartimento di Scienze della Terra “A. Desio”, università degli Studi di Milano, Italia (guglielmina.diolaiuti@unimi.it)

Claudio Smiraglia

Dipartimento di Scienze della Terra “A. Desio”, università degli Studi di Milano, Italia (claudio.smiraglia@unimi.it)

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Droits d’auteur

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