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THE DARK SIDE OF THE ICE: GLACIOLOGICAL AND BIOLOGICAL ASPECTS OF SUPRAGLACIAL DEBRIS
Full text linkThis research deals with a multi-disciplinary analysis of the supraglacial debris. Debris significantly influences the evolution of glacier surface, its energy balance, and the carbon fluxes and storage. In this work through a multi-disciplinary approach, we focused on this dark side of the glaciers from two different points of view: the glaciological and the biological one.
In the last decades, the large majority of glaciers, including those on the Italian Alps, showed a great increase of supraglacial debris cover. The analyses performed on aerial and UAVs imagery on a wide glacierized sector of Italy, highlighted that the debris-covered area doubled in the period 2003–2012, reaching an increase up to 30.10% of the whole glacier area. However, these changes in surface features, fed by an increased availability of debris, occurred with different patches, according to the physical properties of the bedrocks hosting the glaciers. This suggests that further studies are needed to quantify the occurrence and distribution of supraglacial debris on all the Italian glaciation.
The ice albedo and, consequently, the energy balance of glaciers not only are affected by the presence or absence of a thick and continuous debris cover on the glacier surface, but also by the amount and distribution of the fine and sparse debris and dust that discontinuously cover glaciers. Sparse debris is thus important for determining the evolution of ice bodies, but its quantification is arduous, as the availability of high-resolution imagery, both from satellite and UAV, is mandatory. In this work we showed that the processing of an UAV image of the glacier through a segmentation approach allows describing ice features at a small-scale, including the distribution of fine debris. Moreover, we found evidence of darkening phenomena due to an increased amount of fine and sparse debris on the surface of glaciers.
The darkening of glaciers is probably favoring organisms living in the supraglacial debris; however, organisms can promote glacier darkening because they produce dark matter (e.g. humic substances) and are themselves part of the dark debris quantified in glaciological analyses. A positive feedback seems therefore to occur on glacier surface, promoting the increase of supraglacial debris. The analyses of the life on supraglacial debris indicates that a glacier cannot be considered as an isolated environment, although it has different characteristics than the surrounding areas. Nematodes and Rotifers, for instance, can diffusely colonize supraglacial debris only in the presence of allochthonous organic matter, which represents the main source of organic carbon for these organisms in supraglacial environments where primary producers are scarce.
Moreover, the study of bacterial communities in snow highlighted a possible contribution of organisms transported from the area where the air masses originated, as well as a non-negligible input of local air bacteria, maybe due to the deposition of local particulate during snowfall. This strong relation between glacier and ice-marginal environments is observable also from the bacterial community of the cryoconite holes. Indeed, we showed that ice-marginal environments may act as sources of bacteria for these micro habitats, but differences in environmental conditions limit the number of bacterial strains that may survive in them. At the same time, cryoconite holes host some organisms that were not found in any ice-marginal environment we sampled, thus suggesting that some bacteria may reach cryoconite from distant sources. These bacterial communities of cryoconite holes have a wide temporal evolution throughout an ablation season, with autotrophic Cyanobacteria populations dominating communities after snow melt, and heterotrophic populations increasing in abundance later in the season.
The complex bacterial communities that inhabit glacier surface have large impacts on biogeochemical processes, in particular on the carbon cycle. In fact, we provided evidence for the occurrence in these environments of metabolic pathways that differ from those of oxygenic phototrophs and the respiration of heterotrophic organisms beforehand described on glacier surface. Indeed, we observed high abundance of heterotrophic anoxygenic phototrophs, suggesting that light might supplement the energy needed by the organisms permitting them to use some organic molecules as carbon sources. Furthermore, these communities could produce CO2 also by the oxidation of CO, which may be produced by photodegradation of organic matter present in the cryoconite. Finally, we investigated the fate of contaminants on the glaciers surface assessing a key role of the bacteria in the chlorpyrifos degradation.
In summary, the results presented in this PhD thesis improved our knowledge of the supraglacial debris, its components and its evolution. The double view on the glacier system, both glaciological and biological, permits a deeper description of the mutual relations between bio and geo components
High-resolution mapping of glacier surface features. The UAV survey of the Forni Glacier (Stelvio National Park, Italy)
Full text linkFast, reliable and accurate methods for glacier mapping are necessary for understanding glacier dynamics and evolution and assessing their response to climate change. Conventional semi-automatic approaches are based on medium-resolution satellite images, but their use can cause significant loss of accuracy when analyzing small glaciers, which are predominant in the Alps. In this paper, we present a semi-automatic segmentation approach based on very high-resolution visible RGB images acquired from a UAV (Unmanned Aerial Vehicle) survey of the Fomi Glacier, in the Italian Alps, using an off-the-shelf digital camera. The method has the ability to map large-scale morphological features, i.e. bare ice and medial moraines, with better accuracy than methods relying on medium-resolution satellite imagery, with only slight misclassification at the margins. By using segmentation, we also mapped small-scale morphologies not discernible on satellite images, including epiglacial lakes and snow patches, in a semi-automatic way. On a small portion of the eastern ablation tongue, featuring homogeneous illumination conditions, we also investigated in finer detail the occurrence of fine and sparse debris and tested a texture filter technique for mapping crevasses, which showed promising results. Our analyses confirm that the glacier is undergoing intense dynamic processes, including darkening of the ablation tongue and increased surface instability, and show the potential of UAVs to revolutionize glaciological studies. We suggest that by using a combination of different payloads, mapping of glacier features via UAVs could reach high levels of accuracy and speed, making them useful tools for glacier inventories and geomorphological maps
The new Italian Glacier inventory: a didactic tool for a better knowledge of the natural Alpine environment
No full textA glacier inventory is an important instrument to better know the Alpine glacierized environment. After the glacier inventory realized by the Comitato Glaciologico Italiano (CGI, 1959-1962), only regional and local glacier inventories have been developed. In this work, we briefly present the New Italian Glacier Inventory which has been developed by analyzing high resolution color orthophotos acquired in the 2005-2011 time frame. In the New Italian Glacier Inventory 903 glaciers are listed, covering a total area of 369.90 km2. The largest part of the glacier area is located in the Aosta Valley Region (36.15% of the total), followed by the Lombardy Region (23.71%) and by the Province of Bolzano (23.01%). The highest number of glaciers is in Lombardy (230), followed by the Province of Bolzano (212), the Region
of Aosta Valley (192), the Province of Trento (115). About 84% of the total glacier inventory is given by glaciers under 0.5 km2 covering only 21% of the total area. Glaciers wider than 1 km2 are about 9.4% of the inventory, but they cover 67.8% of the total area. In the biggest size class (>10 km2) three glaciers are found. Only 25 glaciers (2.8% of the census as a whole) were classified as “valley glacier” and the
largest part (57.3%) was classified as “mountain glacier” and “glacieret” (40%), confirming that the Italian glacier resource is distributed into many small ice bodies with only a few large glaciers
The evolution of the Italian glaciers from the previous data base to the new Italian inventory : preliminary considerations and results
No full textA glacier inventory is a fundamental tool for describing and managing
the Alpine glacierized environment and evaluating the impacts of
the ongoing climate change. After the 1959-1962 Italian glacier inventory
published by the Italian Glaciological Committee (CGI) in cooperation
with the National Research Council (CNR), only regional glacier lists
have been developed in Italy, thus giving partial pictures of the evolution
of the Italian glaciers. In this work, we summarized the main results
from the New Italian Glacier Inventory, a national glacier atlas recently
completed and based on the analysis of high resolution color orthophotos
which were acquired in the time frame 2005-2011. In the New Italian
Glacier Inventory 903 glaciers are described, covering a total area of
369.90 km2 ± 2%. The largest part of the glacier coverage is located in the
Aosta Valley Autonomous Region (36.15 % of the total), followed by the
Lombardy Region (23.71 %) and the Autonomous Province of Bolzano
(23.01 %). The highest number of glaciers was found in Lombardy (230),
then in the Autonomous Province of Bolzano (212), in the Aosta Valley
Autonomous Region (192), and in the Autonomous Province of Trento km2 covering only the 21% of the total area. Glaciers wider than 1 km2
are 9.4 % of the whole number, but they cover 67.8 % of the total area.
In the widest size class (>10 km2), only three glaciers are found. Only 25
glaciers (2.8 % of the census) were classified as “valley glacier”, while the
largest part (57.3%) was classified as “mountain glacier” and “glacieret”
(40%), thus underlining that the Italian glaciers are spread into several
small ice bodies with few larger glaciers. A first comparison between the
total area reported in the New Italian Glacier Inventory and the value
reported in the CGI –CNR Inventory (1959-1962) suggests an overall
reduction of the glacier coverage of about 30% (from 526.88 km2 in the
Sixties to 369.90 km2 in the present time). A second comparison was
performed with the WGI (World Glacier Inventory) dataset which in the
Eighties listed 1381 Italian glaciers covering a total area of 608.56 km2.
This comparison suggests a loss of 478 glaciers and an area reduction of
238.66 km2 (-39 %)
Estimating ice albedo from fine debris cover quantified by a semi-automatic method: the case study of Forni Glacier, Italian Alps
Full text linkIn 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)
A first approach to detect supraglacial vegetation coverage on debris-covered glaciers using aerial photographs and satellite images: the case study of Miage Glacier
No full textEvaluating high-resolution remote sensing data for reconstructing the recent evolution of supra glacial debris : a study in the Central Alps (Stelvio Park, Italy)
No full textOver the last decades, the expansion of supraglacial debris on worldwide mountain glaciers has been reported. Nevertheless, works dealing with the detection and mapping of supraglacial debris and detailed analyses aimed at identifying the temporal and spatial trends affecting glacier debris cover are still limited. In this study, we used different remote sensing sources to detect and map the supraglacial debris cover, to analyze its evolution, and to assess the potential of different remote-sensed image data. We performed our analyses on the glaciers of Ortles-Cevedale Group (Stelvio Park, Italy), one of the most representative glacierized sectors of the European Alps. High-resolution airborne orthophotos (pixel size 0.5 m 0.5 m) acquired during the summer season in the years 2003, 2007, and 2012 permitted to map in detail, with an error lower than +5%, the supraglacial debris cover through a maximumlikelihood classification. Our findings suggest that over the period 2003–2012, supraglacial debris cover increased from16.7% to 30.1% of the total glacier area. On Forni Glacier we extended these quantification thanks to the availability of UAV (unmanned aerial vehicle) orthophotos from 2014 and 2015 (pixel size 0.15 m 0.15 m): this detailed analysis permitted to confirm debris is increasing on the glacier melting surface (þ20.4%) and confirms the requirement of high-resolution data in debris mapping on Alpine glaciers. Finally, we also checked the suitability of medium-resolution Landsat ETMþ data and Sentinel 2 data to map debris in a typical Alpine glaciation scenario where small ice bodies (<0.5 km2) are the majority. The results we obtained suggest that medium-resolution data are not suitable for a detailed description and evaluation of supraglacial debris cover in the Alpine scenario, nevertheless Sentinel 2 proved to be appropriate for a preliminary mapping of the main debris features
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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