The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results
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Base (topology)
Glacier mass balance
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The recent rapid mass loss of mountain glaciers in response to climate warming has been reported for high and low latitudes all over the Earth. The paper analyses and discusses the recent evolution of a representative glacierized group within the Italian Alps, the Piazzi—Dosdè, where small glaciers are experiencing considerable retreat and shrinking. We analysed aerial photos to calculate area and geometry changes in the time window 1954—2003, and glaciological and geomorphological surveys were also performed. The estimated area change during 1954—2003 was —3.97 km 2 (—51% of the area coverage in 1954). Area reduction increased more recently: area change during 1991—2003 (12 years) was —1.74 km 2 , against —0.67 km 2 during 1981—1991 (10 years), and —1.57 km 2 during 1954—1981 (27 years). Moreover, analysis of the most recent orthophotos acquired during the summer of 2003 under exceptional conditions (i.e. total absence of snow cover) allowed observation and mapping of changes affecting glacier shape and morphology, including growing rock outcrops, tongue separations, formation of proglacial lakes, increasing supraglacial debris and collapse structures. Such processes cause positive feedbacks that accelerate further glacier disintegration once they appear. From a geodynamical perspective, the Dosdè Piazzi is now experiencing transition from a glacial system to a paraglacial one; areas where in the past the shaping and driving factors were glaciers are now subject to the action of melting water, slope evolution and periglacial processes.
Glacier mass balance
Rock glacier
Glacier morphology
Cirque glacier
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.This paper describes the recent evolution of Italian glaciers through an analysis of all available terminus fluctuation data that the authors have entered in a glaciers database (named GLAD) containing 883 records collected on glaciers from 1908 to 2002. Furthermore, a representative subset of data (249 glaciers located in Lombardy) was analysed regarding surface area changes.For the analysis of terminus fluctuations, the glaciers were sorted by size classes according to length. The data showed that during the 20th century Italian Alpine glaciers underwent a generalized retreat, with one distinct and well documented readvance episode that occurred between the 1970s and mid‐1980s, and a poorly documented one around the early 1920s. The rates of terminus advance and retreat have changed without significant delays for the larger glaciers with respect to the smaller ones. However, the smaller the glacier, the more limited the advance (if any) during the 1970s and early 1980s. The behaviour of glaciers shorter than 1 km appears to have changed in the last decade, and between 1993 and 2002 they retreated at a very high rate.The analysis of the subset of data led to a quanti‐fication of surface reduction of c. 10% from 1992 to 1999 for glaciers in Lombardy. Small glaciers proved to contribute strongly to total area loss: in 1999, 232 glaciers (c. 90% of the total) were smaller than 1 km2, covering 27.2 km2 (less than 30% of the total area), but accounted for 58% of the total loss in area (they had lost 7.4 km2).
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Abstract. In spite of the quite abundant literature focusing on fine debris deposition over glacier accumulation areas, less attention has been paid to the glacier melting surface. Accordingly, we proposed a novel method based on semi-automatic image analysis to estimate ice albedo from fine debris coverage (d). Our procedure was tested on the surface of a wide Alpine valley glacier (the Forni Glacier, Italy), in summer 2011, 2012 and 2013, acquiring parallel data sets of in situ measurements of ice albedo and high-resolution surface images. Analysis of 51 images yielded d values ranging from 0.01 to 0.63 and albedo was found to vary from 0.06 to 0.32. The estimated d values are in a linear relation with the natural logarithm of measured ice albedo (R = −0.84). The robustness of our approach in evaluating d was analyzed through five sensitivity tests, and we found that it is largely replicable. On the Forni Glacier, we also quantified a mean debris coverage rate (Cr) equal to 6 g m−2 per day during the ablation season of 2013, thus supporting previous studies that describe ongoing darkening phenomena at Alpine debris-free glaciers surface. In addition to debris coverage, we also considered the impact of water (both from melt and rainfall) as a factor that tunes albedo: meltwater occurs during the central hours of the day, decreasing the albedo due to its lower reflectivity; instead, rainfall causes a subsequent mean daily albedo increase slightly higher than 20 %, although it is short-lasting (from 1 to 4 days).
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Glacier mass balance
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Little ice age
Rock glacier
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The transformation of snow to ice mass balance heat budget and climatology structure and deformation of ice hydraulics and glaciers glacier sliding deformation of subglacial till structures and fabrics in glaciers and ice sheets distribution of temperature in glaciers and ice sheets steady flow of glaciers and ice sheets flow of ice shelves and ice streams non-steady flow of glaciers and ice sheets surging and tidewater glaciers ice core studies.
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Shrinkage
Glacier mass balance
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In view of the rapid and accelerating glacier retreat observed in the European Alps during the last decades, the repeated creation of glacier inventories is important to understand the spatio-temporal variability of glacier changes and to support modeling studies. This article presents the latest glacier inventory for the entire Swiss Alps (SGI2010) derived by manual digitization from high-resolution (25 cm) aerial orthophotographs acquired between 2008 and 2011. Its accuracy is assessed by comparing the extents of clean, snow-and/or debris-covered glaciers derived from multiple digitization by several experts. The potential of more precise mapping of debris-covered glaciers is pointed out through the combination of aerial orthophotos with Differential Synthetic Aperture Radar Interferometry (DInSAR) techniques. In order to investigate the accuracy of glacier outlines obtained from medium-resolution satellite remote sensing imagery, a Landsat derived 2003 inventory is directly compared to all glaciers of the eastern Swiss Alps mapped with 2003 aerial orthoimagery. For the Swiss Alps, the total glacierized area mapped for 2010 is 944.3 ±24.1 km2. Resulting area changes are -362.6 km2 (-27.7%, or -0.75% a-1) between 1973 and 2010. It is shown that satellite remote sensing techniques using medium-resolution source data misclassified more than 25% in area of very small glaciers (<0.5 km2). Therefore, use of high-resolution satellite or airborne imagery for future inventory creation in areas dominated by very small glaciers is recommended.
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Rock glacier
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Here three glacier surface area records (years 1975, 1999 and 2005) available for Aosta Valley (western Italian Alps) have been synthesized. The 1975 data have been collected by previous authors who compiled the first Aosta Valley regional glacier database. The 1999 and 2005 surface area data were computed by the authors here combining registered colour orthophotos with differential GPS (DGPS) field measurements. The surface changes of 174 glaciers (those shared within the three records of data) were calculated to describe the recent evolution of a representative subset of Italian glaciers. Aosta Valley glaciers lost 44.3 km 2 during 1975–2005, i.e. c. 27% of the initial area. Small glaciers contributed strongly to total area loss, and during 2005 147 glaciers (c. 84.5% of the studied ones) were smaller than 1 km 2 , covering 20.7 km 2 (c. 17% of the total area), but accounted for 43% of the total loss in area (losing 19 km 2 from 1975 to 2005). The area change rate accelerated recently (1999–2005: mean area loss of c. 2.8 km 2 /year; 1975–1999: mean area loss of c. 1.1 km 2 /year). We then analyse records (1975–2005) of temperature, precipitation and snow cover from three high-altitude (1332 m asl to 3488 m asl) stations within Aosta Valley, to investigate modified climate within the area. We find increasing temperature especially during late spring and summer, and substantially unchanged total precipitation, with marked reduction of snowfall, snow cover, number of snowfall events and duration of continuous snow cover, especially during spring and summer, likely driving shrinking of glacier coverage.
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