Abstract
ABSTRACTWe analysed the recent involution of glaciers in the Bernina group (Italy), which are shrinking thus permitting a rapid enlargement of the forelands. We delimited glacier outlines upon aerial photographs (1954 and 1981 stereo pairs analysed through an optical system) and orthophotos (2003 and 2007 digital imagines directly managed via GIS software). All the obtained data were overlapped and compared. The estimated glacier area change during 1954–2007 was −36.5 ± 2.4% (−16.2 ± 0.4 km2). The changes sped up more recently; in fact, during 1981–1954 (27 years) the variation was −0.206 km2/y, against −0.387 km2/y during 1981–2003 (22 years), and −0.535 km2/y during 2007–2003 (4 years). In the 1954–2007 period, the forelands experienced a continuous increase (+14.7 km2). Moreover, the analysis of the colour orthophotos allowed observations of: (i) changes affecting shape and geometry of glaciers (growing rock outcrops, tongue separations, increasing supraglacial debris and collapse structures) and (ii) main features of glacier forelands (bare rock exposures, debris and sediments and, in the latter case, occurrence of vegetation colonizing such pristine areas). Glacier forelands resulted also subjected to the action of melting water, debris transport, and periglacial processes, with consequences on landscape and geoheritage.
Highlights
Glacier shrinkage is severe upon the Alps and it is likely driven by the rapid increase in air temperature during the last few decades (IPCC, 2013)
This increase is caused by fragmentation of previous larger glaciers, which generates smaller ones, and it is typical of the ongoing deglaciation phase
A similar behaviour was reported, for example, by Knoll and Kerschner (2009) for the Tyrolean glaciers (Eastern Alps) where more than smaller 50 glaciers derived from the disintegration of previously larger ones, and by Diolaiuti, Maragno, D’Agata, Smiraglia, and Bocchiola (2011) for Dosdè Piazzi glaciers analysed in the time window 1954–2003
Summary
The retreat of glaciers, from Alpine areas (Haeberli & Beniston, 1998) to Antarctica (Cook, Fox, Vaughan, & Ferrigno, 2005; Frezzotti & Orombelli, 2014; Rott, Skvarca, & Nagler, 1996), during the last few decades, is widely reported as a clear and unambiguous sign of global warming (Oerlemans, 2005). The newly exposed areas show the beginning of soil development (D’Amico, Freppaz, Leonelli, Bonifacio, & Zanini, 2015; Egli, Wernli, Kneisel, & Haeberli, 2006) both on sparse till deposits and on wellshaped moraine ridges (Kabala & Zapart, 2012); the chrono-sequences at the glacier forelands represent favourable substrates for biological colonization; these pristine areas show successions of: arthropods (e.g., carabides, Schlegel & Riesen, 2012) delayed by different environmental factors (Brambilla & Gobbi, 2014; Gobbi et al, 2007), bacterial communities (Meola, Lazzaro, & Zeyer, 2014), yeasts (Turchetti et al, 2008), plants (e.g., Cannone et al, 2008; Moreau, Mercier, Laffly, & Roussel, 2006) and trees (Garavaglia, Pelfini, & Bollati, 2010, Garavaglia, Pelfini, & Motta, 2010) In this contribution we summarized the ongoing (i.e., last 50 years) trend affecting an important Alpine glacierized group (namely, Bernina Group), characterized by strong and accelerating glacier decrease and the consequent widening of the glacier forelands. The Bernina massif has been previously studied by geologists, geographers, ecologists, botanists, etc. for the peculiarity of the region mainly with respect to its Swiss sector (see references cited in the following paragraph) suggesting to analyse and describe the Italian side as well
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