- Some evidences of recent and holocenic evolution of the cryosphere in Friuli Venezia Giulia (Italy)
- Colucci, Renato
Subject
- mountain permafrost
- cryosphere
- glaciers
- rockglaciers
- lidar
- gpr
- periglacial
- SCIENZE AMBIENTALI (AMBIENTE FISICO, MARINO E COSTIERO)
- GEO/04 GEOGRAFIA FISICA E GEOMORFOLOGIA
Description
- 2011/2012
- The cryosphere, an integrated part of the Earth system, refers to that portion of the physical world that exists in its frozen state. Ice caps, sea ice, icebergs, lake ice, snow cover, ground ice, glaciers and ice sheets and shelves obviously belong to this set. It also comprises all those parts of territory which, though not presenting water in solid state, always maintain temperatures below zero (i.e. permafrost environments). Studies on the cryosphere of Friuli Venezia Giulia were almost always referred to the attempt of reconstructing the major glacial phasesof the Pleistocene period. The only studied aspect of today’s cryosphere is that of the small glaciers of the Julian Alps, on which terminus shrinkage or advances measurements were taken since the end of the 19th century. The fact that today’s cryosphere isn’t studied that much is probably due to its scarcity compared to other sectors of the Alps. This work intends to fill this gap, trying to characterise as best as possible the present state of the cryosphere on the Friuli Venezia Giulia territory. In order to do so the whole mountain territory of Friuli Venezia Giulia was taken into consideration, ultimately focusing on two distinct sectors: the Julian Alps (south-east area), which hosts the last glacial remains on the Canin and Montasiomassifs, and the Carnic sector of the Alps (north-west area). The latter is the only one that was involved in a survey aiming at the characterisation of mountain permafrost, due to investigations made to realise the rock glaciers inventory of the Italian Alps. A third aspect, still not deeply analysed also on a global level though potentially capable of bringing crucial developments in the future, is that of permanent ice deposits inside cavities. The so named IceCaves are just one of several peculiar phenomena which show a reaction to climate and somewhat sparse research over the past few decades has shown that ice in temperate caves holds similar and complementary secrets to ice elsewhere. Friuli Venezia Giulia contains a great number of cavities (over 7000) also at high altitudes, since of the almost 5000km2 mountain area 1900 are interested by carbonate rocks (limestones and dolostones). This work therefore focuses on the following three aspects: define the present-day state of glacial remains on Mount Canin, also to test new methodologies; update the rock glaciers national inventory thanks to the recent and ongoing developments in earth observation techniques and related geoinformatics; finally, begin a systematic monitoring of cavities with permanent ice remains. As far as the Canin glaciers are concerned the attention focused on the Canin Orientale glacier, actually representing one of the lowermost glaciers of the Alpine chain. A combined strategy involving Ground Penetrating Radar (GPR) and Light Detection And Ranging (LiDAR) technologies was used. GPR profiles were performed during Autumn 2011, to reveal the thicknesses of the glacier, test a methodology to image the internal structure and to estimate the volume of main glaciological units. LiDAR surveys on the area of the Canin Orientale glacier were purposely performed at the same time of the GPR surveys, to allow the creation of a complete and highly precise data set also from a topographic point of view. Thanks to a further LiDAR survey undertaken in 2006 by the Civil Defence of Friuli Venezia Giulia and integrating GPR measurements with these LiDAR surveys, we also quantified the volumetric variations of the glacier from 2006 to 2011. The revision of the Friuli Venezia Giulia part of the Italian rock glacier inventory was performed using both GIS techniques and activity on field. Aerial Orthorectified photographs (orthophotos) at high (2006 – 2009) and low (1998 and 2003) resolutions were used. A high resolution digital terrain model (DTM) was also used (cell size: 1m) interpolated from Aerial laser scannings (LiDAR) acquired between September 2006 and 2009 by the Civil Defence of Friuli Venezia Giulia. Terrain attributes (geometrical and spatial) were evaluated by using ArcGis10 software and its tools. Oblique terrestrial view (pseudo-3D image) of the DTM-hillshadehas been very useful in terms of interpretation of the topography and identification of lobes and shapes. The revision of this inventory uses the morphological classification by Barsch (1996) without taking in account the eventual mobilization of the landforms,and comprehends both rock glaciers and protalus ramparts, the latter taken into consideration for the first time on the Friuli Venezia Giulia territory. Results were analysed from a merely statistic point of view and then related to climate settings, testing the accuracy of a number of existing permafrost distribution models. To face the study of the underground cryosphere it was decided to install instruments in a cavity that would be suitable for the purpose. Attention mainly focused on monitoring the air temperature in several points of the cavity, the temperature of rock at several depths (2cm, 30cm and 100cm) to understand the evolution through time, and the temperature of ice. Moreover two benchmarks were placed to evaluate possible mass variations of the ice deposit. Again, in order to evaluate the thickness of ice and the internal stratifications, GPR was used in the above cave, as well as in another cave not installed with instruments as much. In view of performing further, more detailed inspections on ice in the future, a full stratigraphy of the visible layers on one side of the ice body was executed, together with an analysis of some clay samples extracted from the ice (X-ray difrattometer, LOI). Furthermore, to define the distribution of underground cryosphere in Friuli Venezia Giulia, all caves reporting the presence of snow, ice-snow and only ice were selected from the regional cave inventory of Friuli Venezia Giulia, therefore creating a useful working tool to start from for future studies. Despite of the gap of knowledge on the frozen karst caves in the area, all this instrumental and direct observations could provide a useful key to understand the permafrost distribution and its connections with the underground cryosphere and the glaciological evolution of the landscape.
- XXV Ciclo
- 1971
Date
- 2013-05-10T08:52:26Z
- 2013-05-10T08:52:26Z
- 2013-04-24
Type
- Doctoral Thesis
Format
- application/pdf
Identifier
urn:nbn:it:units-10082