current transition from glacial to periglacial processes in the dolomites (south-eastern alps)
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CurrenttransitionfromglacialtoperiglacialprocessesintheDolomites(South-EasternAlps)
ARTICLEinGEOMORPHOLOGY·JANUARY2015
ImpactFactor:2.79·DOI:10.1016/j.geomorph.2014.08.025
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RobertoSeppi
UniversityofPavia
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AldinoBondesan
UniversityofPadova
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RobertoFrancese
UniversitàdeglistudidiParma
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AndreaNinfo
UniversityofPadova
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Geomorphology 228 (2015) 71–86
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Geomorphology
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Current transition from glacial to periglacial processes in the Dolomites(South-Eastern Alps)
R. Seppi a,⁎, T. Zanoner b, A. Carton b, A. Bondesan b, R. Francese c, L. Carturan d, M. Zumiani e,M. Giorgi c, A. Ninfo b
a Dipartimento di Scienze della Terra e dell'Ambiente, Università di Pavia, Via Ferrata 1, 27100 Pavia, Italyb Dipartimento di Geoscienze, Università di Padova, Via Gradenigo 6, 35123 Padova, Italyc Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Borgo Grotta Gigante 42/C, 34010 Sgonico, TS, Italyd Dipartimento Territorio e Sistemi Agro Forestali, Università di Padova, Viale dell'Università 16, 35020 Legnaro, PD, Italye Servizio Geologico, Provincia Autonoma di Trento, Via Roma 50, 38122 Trento, Italy
⁎ Corresponding author. Tel.: +39 0382 985833 (officeE-mail address: [email protected] (R. Seppi).
http://dx.doi.org/10.1016/j.geomorph.2014.08.0250169-555X/© 2014 Elsevier B.V. All rights reserved.
a b s t r a c t
a r t i c l e i n f oArticle history:Received 13 February 2014Received in revised form 30 July 2014Accepted 28 August 2014Available online 6 September 2014
Keywords:Composite landformDebris-covered glacierPermafrostGround surface temperatureGeophysical surveysDolomites
A close relationship between glacial and periglacial landforms is frequently observed in alpine environments,where a transition from glacial to periglacial processes often took place after the end of the Little Ice Age (LIA).Understanding the origin of these landforms is challenging, and assessing the current spatial domain of glacialand periglacial processes may be a difficult task in high-relief areas, where thick and widespread debris coveroften characterize rapidly decaying glaciers. Herewe present a comprehensive study of a composite landform lo-cated in the Dolomites (South-Eastern Alps), combining geomorphological, geophysical and topographic surveyswith ground surface temperature measurements. Results indicate that a debris-covered glacier persists in theupper part, rather large compared to the LIA extent, but currently inactive and rapidly losing mass. An activerock glacier exists in the lower part, surrounded by discontinuous permafrost. A frozen body about 10 m thickwas detected in the rock glacier and geomorphological evidence suggests that this ice mass is completelydetached from the debris-covered glacier. Our findings suggest that the lower part of the composite landformis probably a remnant of the ancient glacier tongue and is currently evolving under periglacial conditions.Periglacial processes are therefore replacing glacial processes which dominated in this site during the LIA.
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
Geomorphic processes in high-altitudemountain areas are sensitiveto the effects of climate change, which modulate the interactionbetween glacial and periglacial processes (Haeberli, 2005; Harris andMurton, 2005; Keiler et al., 2010; Waller et al., 2012). These two typesof processes may coexist where glaciers develop in permafrost-affected areas, or replace each other in response to glacier fluctuations(Kneisel, 2003; Reynard et al., 2003; Kneisel and Kääb, 2007; Lilleørenet al., 2013).
The coexistence of glaciers and permafrost in mountain areasprimarily depends on the relative position of the ELA (equilibrium linealtitude) with respect to the lower limit of mountain permafrost(Etzelmüller and Hagen, 2005). Where the two limits are close to eachother, the spatial association between glaciers and rock glaciers maybequite complex andmay originate composite landformswhich usuallypresent a glacier or a glacieret in the upper part of the catchment and a
), +39 340 4158248 (mobile).
rock glacier in the lower part. Typically, this situation is inherited fromthe Little Ice Age (LIA) in the Alps. Besides the relative position of theELA, other crucial factors are the amount of annual precipitation andelevation, which control the glacier size and the occurrence ofpermafrost-associated landforms (i.e. the rock glaciers, Humlum,1998; Janke, 2007).
Recent investigations led to the formulation of twomain hypothesesfor the formation of these composite landforms. The rock glacier mayhave been pre-existing to the glacier advance and, after glacier retreat,sedimentary ice may have been embedded in the creeping debris andtransferred downstream by the rock glacier under permafrost condi-tions (Guglielmin et al., 2004; Ribolini et al., 2007, 2010). Otherwise,the rock glacier may have developed from the debris-covered, lowerpart of a shrinking glacier (Whalley and Palmer, 1998; Krainer andMostler, 2000;Monnier et al., 2011, 2013). In both cases, the ice contentof rock glaciers can be highly variable and of diverse origins, becausecongelation icemay form in the ground and creepwith ice of glacial or-igins (Haeberli, 2000). Further geomorphological evidences of the inter-action between glacial and permafrost processes are the pushmoraines,i.e. perennially frozen sediments tectonically disturbed by advancingglaciers, which can be observed at the margins of numerous alpine
72 R. Seppi et al. / Geomorphology 228 (2015) 71–86
glacier forefields (Haeberli, 1979; Lambiel and Delaloye, 2004; Lugonet al., 2004; Kääb and Kneisel, 2006).
Irrespective of their origin, these landforms generally develop inhigh-relief areas with high debris supply from the surrounding slopes.Given the reduced evacuation capacity of the small glaciers and rockglaciers, sediments tend to accumulate originating a thick debris coverwhich protects the underlying glacier ice from ablation (Frauenfelderet al., 2003; Zemp et al., 2005). As a direct consequence, the spatialdomain and the temporal evolution of glacial and periglacial processesoccurring in these areas are often difficult or impossible to assess with-out the use of combined investigations, including geophysical, geodeticand thermal prospection techniques (Lugon et al., 2004; Monnier et al.,2011; Carturan et al., 2013a,b). Modern tools for glacier change detec-tion, such as the multi-temporal comparison of high resolution digitalelevation models (DEMs), can also prove useful in this case (Paul andHaeberli, 2008; Knoll and Kerschner, 2009).
Composite landforms mainly originated by the transition fromglacial to periglacial processes are common in the European Alps andare particularly widespread in the Dolomites (South-Eastern Alps).Present-day glaciers cover an area of about 6.95 km2 in this mountaingroup (estimation of 1999; Cagnati et al., 2002). They are generallysmall cirque glaciers, persisting at low altitude thanks to high accumu-lation rates of avalanche snow, extensive debris coverage and effectivetopographic shading ensured by steep rockwalls. In several cases, cur-rently active rock glaciers developed from the small, retreating debris-covered glaciers as a result of the decreased efficiency in transferringsediments from the glacier to themeltwater (Krainer et al., 2010, 2012).
In the Dolomites, as in most high-relief areas of the Alps, notablegaps exist in the knowledge of i) the current extent of glaciers underthick debris mantles, and ii) the origin, internal structure and dynamicsof composite landforms where interaction between glacial andperiglacial processes occurred in the past or is still active today.
In this workwe present a comprehensive study of a composite land-form located in the Dolomites, aimed at i) establishing the currentspatial domain of glacial and periglacial processes, and ii) investigating
Fig. 1. Geographic setting of th
the main geomorphological processes driving its evolution since theLIA. The main hypothesis is that this site has undergone a shift fromglacial to periglacial processes since the LIA, and that the latter are cur-rently dominant.
2. Study site and geomorphological description
The Cima Uomo study site is located in the upper Val San Nicolò, atributary of Val di Fassa (Dolomites, South-Eastern Alps, Fig. 1). Recentlythis mountain group has been included in the UNESCOWorld HeritageList, because of its exceptional beauty and unique landscape, togetherwith its scientific importance from the geological and geomorphologicalpoint of view (Gianolla et al., 2008). We focused on a compositelandform (coordinates: 46° 24′ 35″ N, 11° 48′ 25″ E) which occupies acirque exposed to the northwest and surrounded by steep rockwallspeaking at Cima Uomo (3006 m a.s.l.) (Fig. 2a). The landform rangesin elevation from 2390 to 2710 m a.s.l. The area is characterized by theoutcrop of carbonate rocks, mainly limestones of middle Triassic age(Calcare della Marmolada), frequently intercalated by volcanic dykes(Blendinger, 1985). Because of the bedrock lithology, the area is karsticand surface water circulation is almost totally absent.
The current mean annual air temperature (MAAT) at the meanelevation of the composite landform (2510 m a.s.l.) was calculatedfrom the data of an automatic weather station (AWS) located about7 km south (PassoValles, 2020 m a.s.l.), applying a standard verticallapse rate of 0.65 °C/100 m. It was −1.8 °C, 0.5 °C and 0.0 °C in 2010,2011 and 2012, respectively.
In the last centuries the study site was occupied by the Cima UomoGlacier, whose presence, past extent and debris cover were describedin historical maps and documents. In the 1905 topographic map“Karte der Marmolatagruppe” at the 1:25.000 scale (DuÖAV, 1905,Fig. 3a), which was surveyed in a period close to the end of the LIA(Matthews and Briffa, 2005), the glacier was reported with a triangularshape, an area of about 0.14 km2 and the clean ice terminus at about2460 m a.s.l. Afterwards, the glacier was still mapped as a clean ice
e Cima Uomo study area.
Fig. 2. Photographs of the study area. (a) General view showing the Cima Uomo rock gla-cier (1) and the lateral moraines (2). The black dots indicate the approximate lower limitof the debris-covered glacier. (b) Close-up of the Cima Uomo rock glacier (1) and of thetwo lateral moraines (2). The photograph in (a) was kindly provided by A. Crepaz,ARPAV Regione Veneto.
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body in several editions (from the 1910s to 1950s) of the map “Passo diValles,” edited by the Istituto Geografico Militare at the 1:25.000 scale.Castiglioni (1925) described “Cima dell'Uomo” as a small glacier ofabout 0.20 km2, about half of which was covered by debris (Fig. 3band c). The terminus of the glacierwas at about 2420ma.s.l. and contin-uous debris coverage was estimated to occur below 2550 m a.s.l. Theglacier was also reported in a geological map at 1:12.500 scale(Vardabasso, 1930) and shortly described by Rossi (1962) in a mono-graph on the geology of the Marmolada massif. In the Italian GlacierInventory, compiled in the 1960s, the glacier was classified as extinctand a few avalanche cones were reported in its upper area (CGI,1962). The World Glacier Inventory (code I4L0010116) reported forthis glacier an area of 0.07 km2 and an elevation range of 230 m (from2470 to 2700 m a.s.l.; WGMS, 1989).
A geomorphological sketch map was prepared by drawing thedetected landforms in GIS software (Fig. 4a). Additional help for thegeomorphological mapping came from an orthophoto with a spatialresolution of 0.5 m and a hill-shaded DEM with a ground resolution of2 × 2m, both acquired in 2006. The orthophoto and the DEMwere pro-vided by the Autonomous Province of Trento.
A composite landform is currently observable in the area formerlyoccupied by the Cima Uomo Glacier, which is characterized by fourdifferent, closely related morphological units (Fig. 4b). The remnantsof the glacier constitute the first morphological unit (unit 1), whose ex-istence below an almost continuous debris mantle has been ascertainedduring field surveys carried out in summer 2012. Several outcrops of ice
were detected along meandering furrows and in holes, showing thetypical banding of the sedimentary glacier ice (Fig. 5). The thickness ofthe debris mantle ranged from 25 to N100 cm, mainly consisting ofmatrix-free, angular clasts, ranging in size from a few centimeters tosome tens of centimeters, with a few larger boulders. Reworking bydebris flows was observed in the upper and middle parts of the glacier.
Due to the complete coverage of debris, the current extent of theglacier was not easy to recognize. A first assessment based on field ob-servations of ice outcrops was integrated by geodetic analyses in GISsoftware, differencing two high-resolution LiDAR DEMs acquired inthe late summer of 2003 and 2006. Elevation losses larger than 0.5 mhave been interpreted as being caused by the melting of the buriedice, while areas with negligible elevation changes (b0.5 m) have beeninterpreted as stable deposits, without buried ice (Fig. 6). The 0.5 mthreshold has been chosen as it represents the uncertainty of theDEMs differencing evaluated over stable bedrock. Results indicate thatin 2003 the glacier still occupied the zone between 2460 and 2700 ma.s.l., with an average slope of about 30° and an area of 0.10 km2.3
The secondmorphological unit (unit 2; Fig. 4b), located downstreamof the glacier, is an elongated, deep hollow about 200 m long and 60 mwide, ranging in altitude from 2430 to 2460 m a.s.l. and presenting atthe bottom some landforms similar to fluted moraines. The generalmorphology, the absence of ice outcrops, and the stability of the surface(as revealed byDEMs differencing) suggest the absence of ice below thisdeposit.
The third morphological unit consists of two lateral moraines (unit3; Fig. 4b), approximately 25 m high, which laterally bound the unit 2(Fig. 4c). The left moraine has a sharp crest and very steep flanks, ismore than 500 m long and extends downstream from 2600 m a.s.l. inan SE–NW direction. The right moraine is more complex, with thehighest part consisting of a large lobe extending from 2550 to 2480 ma.s.l. This lobe probably outlines a minor lateral tongue of the CimaUomo Glacier, which developed from its right side during the lastadvance. Further downstream, the moraine takes the form of a lateralridge with a sharp crest, which is about 100 m long and developsfrom 2480 to 2430 m a.s.l. These moraines display some key features(i.e. sharp crests, steep flanks, an absence of vegetation and limited orno lichen cover) analogous to many others in the Alps which were rec-ognized as belonging to the LIA (Baroni and Carton, 1996; Federici et al.,2008; Lucchesi et al., 2014; Carturan et al., 2014). Based on these char-acteristics, we attributed an LIA age to these deposits, which thereforemark the largest extent reached by the Cima Uomo Glacier in thatperiod.
The fourth morphological unit (unit 4; Figs. 2b and 4b) is locateddownstream of unit 2, from an elevation of 2430 to 2400 m a.s.l. Thisarea, which has an average slope of about 19° and exhibits a swollensurface (Fig. 4d), shows well-developed arcuate ridges and furrows,placed side by side and perpendicular to the main axis of the deposit.The surface topography of this area suggests an ongoing creepingprocess of the debris, very similar to what is observed over active rockglaciers. Therefore, according to field evidence, we hypothesize thatthis area might be a rock glacier and as such we have called it the“Cima Uomo rock glacier.”
A close spatial relationship exists between the LIA moraines (unit 3)and the rock glacier (unit 4). The deposit which bounds the lower partof the rock glacier displays morphological continuity with the crests ofthe lateral moraines and the slope angle of its outer side is comparableto that of the outer sides of the moraines. In addition, the plant coloni-zation reveals that this deposit is stable. Based on these observations,wemade the hypothesis that the rock glacier is entirely enclosedwithinthe latero-frontal LIA moraine complex (Fig. 4a).
3. Methods
In order to identify the geomorphic processes responsible of itsevolution, the Cima Uomo composite landform has been investigated
Fig. 3. Historical documents depicting the Cima Uomo Glacier and the surrounding area. (a) Excerpt of the 1905 DuÖAV map “Karte der Marmolatagruppe.” (b and c) Sketch (b) andphotograph (c) of the glacier on 4 September 1924 (Castiglioni, 1925).
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combining different survey techniques, including geophysical and topo-graphicmethods andmeasurements of the ground surface temperature.
3.1. Geophysical surveys
Ground penetrating radar (GPR) and electrical resistivity tomogra-phy (ERT) were used for inspecting the internal structure of the CimaUomo composite landform. These geophysical techniques were indeedreported as suitable methods for inspecting the subsurface characteris-tics and the internal structure of rock glaciers, ice-cored moraines anddebris slopes (Kneisel, 2004; Maurer and Hauck, 2007; Monnier et al.,2011; Scapozza et al., 2011; Monnier et al., 2013; Onaca et al., 2013;Schneider et al., 2013; Kneisel et al., 2014).
The operating principle of the GPRmethod is very similar to the oneof the echo-sounding technique. A large bandwidth electro-magneticpulse generated with an antenna is propagated into the subsurfacewhile a second antenna detects the pulse reflected in correspondenceof contrasts in the electrical impedance. The electrical impedance
depends on the conductivity, the dielectric constant and the magneticpermeability of the subsurface (Schrott and Sass, 2008; Degenhardt,2009).
The ERT method is based on the principle of the electricalquadrupole: two electrodes inject a direct current in the subsurfaceand two other electrodes measure the associated perturbation interms of potential. Several tens of electrodes are managed simulta-neously and combined into a sequence of hundreds of quadrupoles.Each measure represents a value of apparent resistivity that could bedisplayed in the form of a pseudo-section which gives a rough idea ofthe electrical properties of the subsurface (Scapozza and Laigre, 2014).
The geophysical surveys conducted in our study site included a GPRprofile, a 2D ERT profile and a 3D ERT volume (Fig. 7a). The campaignwas conducted in late August 2012 and focused on the middle andlower parts of the investigated landform. In particular, the ERTmeasure-mentswere limited to the rock glacier (unit 4; Fig. 4b),whereas the GPRprofile included the central part of the landform (unit 2; Fig. 4b). The 2DERT profile was coupled for its entire length to the lower part of the GPR
Fig. 4. Landform characteristics of the study area. (a) Geomorphological map. (b) Four morphological units recognized in the composite landform (see text for details). (c andd) Topographic profiles crossing the lateralmoraines (B–B′) and the CimaUomo rock glacier (A–A′) (for interpretation of the references to color in thisfigure legend, the reader is referredto the web version of the article).
Fig. 5. Ice outcrops on the surface of the Cima Uomo debris-covered glacier in summer 2012. Note the banded structure of the ice.
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Fig. 6. Elevation change between 2003 and 2006 of the CimaUomo composite landformobtained fromDEMs differencing. TheDEMswere provided by theAutonomous Province of Trento(for interpretation of the references to color in this figure legend, the reader is referred to the web version of the article).
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profile, with a lateral offset of about 6m. The coordinates along the pro-files were surveyed using a differential GPS associated with a robotictotal station.
Radar measurements were carried out using a GSSI SIR 2000 systemequipped with a 80 MHz unshielded antenna. The bandwidth of theantenna is approximately 140 MHz and the wavelength in ice couldbe estimated to be 1.8–2.0 m. The resolving power of such a configura-tion, using the λ/4 criterion (Yilmaz, 1987), is around 0.5m, but it couldbe prudentially limited to 1.0 m.
Resistivity data were collected with a 48-electrode IRIS SyscalR1 georesistivimeter. Electrode spacing in the 2D ERT was set to3 m while the measurements were conducted using the Wenner-alpha configuration. This arrangement was chosen because it pro-vides the highest signal-to-noise ratio between all the differentquadrupoles.
The 3D ERT survey was carried out using the same 48 electrodes ofthe 2D line and six additional remote poles in a pole-dipole configura-tion. In the first session the current was injected through the first re-mote pole and, one by one, through the 48 electrodes of the line, usingthe other 47 for voltage measurements. Six sessions were performed,one for each remote pole. This relatively new approach has been suc-cessfully used on large alpine landslides (Nyquist and Roth, 2005;Francese et al., 2013).
Radar data, including positioning, were processed in an open-sourceenvironment using the public domain package Seismic Unix (ColoradoSchool ofMines—Center forWave Phenomena) and somenew routineswere specifically coded to handle GPR scans. The major processingsteps were DC component removal, zero offset correction, verticaland horizontal filtering and amplitude recovery using a linear gainfunction. A specific effort was devoted to correct the different eleva-tion of the radar sweeps along the profile and to attenuate the ringycharacter of the scanlines. The final section was inverted to depthassuming a two-layer architecture. The velocity in the upper layerwas set to 0.12 m ns−1 using the resistivity image as a constraint.The velocity in the lower layer was estimated by analyzing themove-out of some diffraction hyperbolas and resulted approximately0.15 m ns−1, which is a typical value for several alpine rock glaciers(Hausmann et al., 2007).
Resistivity data were processed using the Ertlab3D and the TomoLabsoftware packages. Pre-processing consisted of noise removal andassigning field geometry. Compared to other commercial packageswhich generally use a cubic grid, this package uses a modeling algo-rithm based on finite tetrahedrical elements. The possibility of properlymodeling the topography and the flexibility of the finite elements inbuilding the mesh result in resistivity models with smoother andmore realistic geologic boundaries as compared to other inversionschemes where the algorithm in the attempt to fit the field mea-sures often generates sharp and unrealistic boundaries (Loke andBarker, 1996).
A rapid convergence of the model response to field data was alwaysobserved during the inversion process, and the misfit that resulted wasnegligible. The inverted values exhibiting a normalized depth of investi-gation (DOI; Oldenburg and Li, 1999) index larger than 0.2 were not in-cluded in the output.
3.2. Topographic surveys
A monitoring network was established in 2010 in order to measurethe horizontal and vertical displacement of the Cima Uomo rock glacier.Fourteen benchmarks (topographic steel screws) were placed on largeboulders, aligned along three transverse profiles ~50 m from eachother (Fig. 7a). A primary station and two additional reference sta-tions were located on stable bedrock outside the investigated land-form and marked with survey nails. The position of the boulderswas surveyed on 24 August 2012 using a geodimeter (Robotic TotalStation Trimble 5600 DR200+) equipped with a Trimble RMT 604Remote Target 360 Degree power prism. The geodimeter with a sin-gle prism has a range of about 5.000 m with an accuracy in standardmode of ±2 mm +2 ppm, while the angle measurement accuracy is3″ (1.0 mgon).
The primary and the reference stations were surveyed using twoTrimble R7GNSSGPS receivers equippedwith Zephyr-2 geodetic anten-nas. The precision of this GPS system in terms of root mean square(RMS) error is 3 mm +0.1 ppm horizontally and 3.5 mm +0.4 ppmvertically. Themeasurements were carried out in the real time kinematic(RTK)mode. Themaster stationwas surveyed in virtual reference station
Fig. 7.Observation network on the CimaUomo composite landform. (a) Geophysical and topographic survey networks. (b) GSTmeasurement sites. The outlined area in (b) represents thelimit of the area shown in (a).
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(VRS) mode using the Network of Transport of RTCM through InternetProtocol (NTRIP) provided by Stonex. Data were converted fromlongitude/latitude onto the WGS84 UTM32 reference system with aproprietary code developed by the National Institute of Oceanographyand Experimental Geophysics of Trieste, based on a novel, high resolu-tion geoid (Sterzai et al., 2007).
3.3. Ground temperature measurements
The bottom temperature of the winter snow cover (BTS) methodwas first designed and described by Haeberli (1973) and is often usedto provide a first assessment of the spatial distribution of permafrost.The thresholds generally used for interpreting BTS measurements are
Fig. 8. Results of the ERT and GPR profiles. The location of the two profiles is shown inFig. 7a (for interpretation of the references to color in this figure legend, the reader isreferred to the web version of the article).
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−2 °C for permafrost possible and −3 °C for permafrost probable.Values higher than −2 °C mean unlikely permafrost (Hoelzle, 1992;Julián and Chueca, 2007; Bodin, 2013; Onaca et al., 2013). Recentworks questioned the use of fixed thresholds for interpreting BTSmeasurements, because they depend on many controlling factors suchas terrain grain size, topographic position, snow mantle history, andair advection processes (Delaloye, 2004; Lambiel, 2006). According tothese authors, BTS measurements enable the identification of homoge-neous areas of cold andwarm ground temperatures and cannot be usedto directly infer the presence or absence of permafrost. Moreover, BTSmeasurements should be preferably repeated for several years overthe same area in order to capture the interannual variability (Lambieland Pieracci, 2008), and combinedwith continuous recording of groundsurface temperatures (GST) using dataloggers, because the shape of thewinter GST curve provides useful information on the presence/absenceof permafrost (Hoelzle et al., 1999; Ishikawa, 2003; Gądek and Kędzia,2008; Apaloo et al., 2012).
In our study area, BTS measurements were performed using a3-m-long aluminum probe equipped with a Pt 100 class A thermistoron the tip. The probe has an accuracy of ±1% and a resolution of0.1 °C and its calibration was tested each year before measurements.The surveys were carried out on 24 April 2009, 2 April 2010 and 7April 2011. The measurements were performed where the snowpackwas thicker than 1 m and the position of each BTS measurement pointwas surveyed with an accuracy of ±5 m using a GPS (Leica System1200 GRX).
GST recording was performed using eight miniature temperaturedataloggers (Tinytag TGP 4020) connected to an external probewith measurement range from −40 to +125 °C, ±0.35 °C of accuracy(between 0 °C and +65 °C), and resolution of 0.02 °C. The calibrationwas assessed each year using the zero curtain temperature in thephase of snowmelt. The devices were installed in early autumn 2009,and since then they have been running regularly, recording tempera-tures at one-hour intervals. The probes of all the dataloggers wereplaced in gravelly terrains without fine matrix and free of vegetation,at a depth ranging from 20 to 35 cm in order to shield them from directsolar radiation. These ground characteristics are representative of themost part of the composite landform. Three dataloggers were placedon the lower part of the landform from 2410 to 2430 m a.s.l. (U01,U02 and U04), in order to investigate the surface thermal regime ofthe rock glacier. Two of them were placed on a convex ridge, and theother on a flat area. The U06 dataloggerwas placed on a flat area locatedon the lateral lobe of the right LIA moraine (2480 m a.s.l.) and the U05was located on the scree slope below this lobe (2440 m a.s.l.). The U09datalogger was setup over the debris-covered glacier (2495 m a.s.l.),while two additional sites were chosen outside the investigated land-form to investigate the ground thermal conditions on a steep, coarse-grained scree slope (U08, 2475 m a.s.l.) and on a ridge composed ofglacial debris (U10, 2565 m a.s.l.) (Fig. 7b).
Relevant parameters for the assessment of the ground thermalregime, and the possible occurrence of permafrost, were extractedfrom the GST data, i.e. MAGST (mean annual ground surface tempera-ture), GFI (ground freezing index), and WEqT (winter equilibriumtemperature) (Delaloye, 2004; Bodin, 2013; PERMOS, 2013).
4. Results
4.1. Geophysical surveys
The GPR profile and its interpretation are shown in Figs. 8 and 9. Acurved reflector is clearly visible in the distance interval between 50and 200 m (Fig. 8). The dipping and concave reflecting horizon marksa subsurface geometry which is probably referable to the lower limitof a frozen body. Conversely, the prominent reflection at 25–50 m isnot a primary signal and is caused by severe ringing (Fig. 9), likely dueto a local poor coupling between the antenna and the ground surface.
The reflectivity is quite low in all the other segments of the profile(0–25 m and 200–350 m, RRP zones in Fig. 9), probably because theradar wave was highly attenuated by the presence of a shallow surfacelayer consisting of pebbles in a moistened silty matrix.
The overall resistivity in the 2D ERT profile ranges from 3 to265 kΩ m (Fig. 8). In the lower part of the profile (0–50 m), the near-surface resistivity is around 3 kΩ m and increases to 15–20 kΩ m atgreater depths. A three layer structure is observable from a distance ofabout 50 m along the ERT profile, with a near-surface layer (~2.5 mthick) exhibiting resistivity values ranging from 3 to 15–20 kΩ m andan inner layer withmaximum values higher than 250 kΩm. This highlyresistive body, whose maximum thickness exceeds 10 m, shows anelongated shape and its top is approximately parallel to the surface. Athird layer with resistivity values around 50 kΩ m is observable underthe highly resistive body.
The overlay of the radar signature and the ERT profile shows closecorrespondence between the major radar reflecting horizons (MRRH)and the layer within the rock glacier characterized by sharp resistivitycontrasts (Fig. 9). A resistivity threshold around 80 kΩ m betweenfrozen and unfrozen sediments is suggested by the MRRH interface. Abetter image of the geometry of the buried frozen body is visible inthe 3D ERT volume (Fig. 10a), which shows its three-dimensionalshape outlined by the above-mentioned threshold value of 80 kΩ m.The frozen body looks like an ensemble of several lobeswith an estimat-ed maximum thickness of 15 m in the central part (Fig. 10b). Theprojected surface of the frozen body is about 4650m2, while the volumecan be estimated to be approximately 23000 m3.
4.2. Surface displacement
The surface displacement of the Cima Uomo rock glacier over a peri-od of about 2 years (29 September 2010 to 24 August 2012) is shown inFig. 11. The displacement directions are almost parallel to themaximumtopographic gradient and the highest velocities were detected in thecentral upper part of the rock glacier, at the boundary with the deepcentral hollow (morphological unit 2) (Fig. 11). The velocity rangesfrom 0.08 to 0.22 m year−1, with a decreasing rate towards the frontalarea and along the flanks. On the left flank and along the frontal rimthe displacement directions diverge, according to the curvature of thelobe. A vertical lowering ranging from 0.06 m year−1 in the lower partof the rock glacier to 0.19 m year−1 in the upper part was also
Fig. 9.Overlay of the ERT profile on the interpretedGPRprofile.MRRH:major radar reflecting horizons. RRP: radar reduced penetration zone (for interpretation of the references to color inthis figure legend, the reader is referred to the web version of the article).
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measured. The lowering rates increase from the lower part to the up-slope sector and from the flanks to the centre of the rock glacier.
4.3. Ground temperature
The BTS measurements show large interannual variability, main-ly depending on the thickness and date of appearance of the snow-pack in the months preceding the survey (Fig. 12). Among the3 years of measurements, the second (2010) was the coldest atmost sites. The coldest areas are the scree slope originating fromthe right lateral moraine between 2390 and 2430 m a.s.l., and thescree slope which is located west of the left moraine. BTS valuesare comparatively higher on the rock glacier area (Fig. 12). The ther-mal regime of all the GSTmonitoring sites fromOctober 2009 to Sep-tember 2012 is shown in Fig. 13, along with the evolution of the airtemperature and the snowpack at the AWS of Passo Valles. Somekey parameters calculated from the GST data are shown in Table 1.In the 3 years of measurements, MAGST was above 0 °C at all sites,except in the lower part of the debris-covered glacier (U09) wherevalues below −1 °C were recorded, mainly due to peculiar condi-tions during the snow-free period when the temperature fluctuatedbetween 0 and 1 °C (Fig. 13).
The correlation between MAGST and MAAT was not statisticallysignificant, as shown by the comparatively low MAGST recorded in2011–2012 which was the warmest of the three considered years. The
Fig. 10. Resistivity volumes. (a) Total volume. (b) Volume with values larger than 80 kΩm (forweb version of the article).
least negative GFI values were reached in years 2010–2011 for allthe monitoring sites, whereas the coldest values, ranging from−125 °C·day at U06 to −783 °C·day at U01, were recorded in thethird year. The low MAGST and GFI values recorded in 2011–2012 de-pend on below-average snow cover conditions which occurred in thatwinter (Valt and Cianfarra, 2012). The ground thermal regimes showthat the WEqT phase was reached only in 2010 and 2011 (Fig. 13),while in 2012 high frequency variations of the winter temperatureoccurred atmost sites, due to the above-mentioned conditions of scarceand discontinuous snow cover.
According to theWEqTmeasurements and based on the shape of thetemperature curves, permafrost conditions would exist at most GSTmeasurement sites, both inside and outside the rock glacier, with theexception of U06 and U10 which are located on the LIA glacial deposits.Interestingly, the lowest WEqT value was recorded in the lower part ofthe rock glacier.
5. Discussion
5.1. Surface thermal conditions and permafrost occurrence
According to the alpine permafrost index map (APIM), processedwithin the alpine PermaNET project (Boeckli et al., 2012), permafrostexists in the Cima Uomo area, predominantly in the steep rockwallsand in the area occupied by the debris-covered glacier (Fig. 14). In the
interpretation of the references to color in this figure legend, the reader is referred to the
Fig. 11.Annual horizontal velocity (arrows; length of the arrow in the legend corresponds to 0.1m year−1) and annual vertical lowering (colored dots) of CimaUomo rock glacier. The ERTline (A–B) is also shown (for interpretation of the references to color in this figure legend, the reader is referred to the web version of the article).
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middle and lower sectors (morphological units 2 to 4; see Section 2)permafrost occurs only in very favorable conditions. However, theAPIM gives only a very rough estimation of the potential presence ofpermafrost, as it has not been calibrated with local data.
The ground temperature measurements confirm that discontinu-ous permafrost conditions exist in the Cima Uomo area. GST data(WEqT values and shape of winter temperature curve) provide themost reliable evidence for permafrost occurrence. According tothese results, permafrost would be present in the rock glacier, inthe scree slope originating from the outer side of the right lateralmoraine (site U05), and in the scree slope to the west of the left lat-eral moraine (site U08). In this landform, which is composed of me-dium to large clasts and boulders without interstitial matrix, thecold conditions could be favored by the well-known “thermal anom-aly” characterizing this type of deposits (Harris and Pedersen, 1998;Juliussen and Humlum, 2008). On the contrary, GST data seem to ex-clude the occurrence of permafrost in the lobe of the right lateralmoraine (site U06) and in the debris lobe located at 2570 m a.s.l.(U10 site).
In terms of WEqT values, our findings are similar to those obtain-ed on an active rock glacier located in the Adamello–Presanellagroup, where measurements carried out from 2004 to 2009 showedWEqT ranging from −5 to −3 °C (Seppi et al., 2011). As far as theDolomites are concerned, WEqT ranging from −4 to −9 °C was re-corded in March 2005 and 2006 at the Cadin di Croda Rossa andCadin del Ghiacciaio rock glaciers (Krainer et al., 2010), while similarmeasurements provided temperatures from −4 to −2.5 °C at theMurfreit rock glacier in 2009 (Krainer et al., 2012) and around−4 °C at the Piz Boè rock glacier in February and March 2009(Crepaz et al., 2011).
The above-zero MAGST measurements could be attributed to thethermal offset, i.e. the difference between mean annual temperature
at the permafrost table and the mean annual ground surface tempera-ture (Kneisel and Kääb, 2007). Investigating this thermal phenomenon,Burn and Smith (1988) suggested that permafrost may be in equilibri-um, or aggrading, even with MAGST above 0 °C.
The thermal behavior at U09 may represent the thermal conditionsoccurring in the debris-covered glacier (morphological unit 1). Theprobe of the data logger is buried under 25 cm of debris and lies ap-proximately 5 cm above the glacier ice, whose cooling effect is most-ly evident during the snow-free period (from June to October), whentemperatures are almost stable and slightly above 0 °C. This meansthat the debris layer is not thick enough to prevent the ice ablationduring summer and that the glacier is subject to net ablation, asshown by the comparison of the two DEMs from 2003 and 2006(Fig. 6). On the contrary, during the snow cover period the thermalregime of U09 is very similar to the other GST sites, in particularwith those located on the rock glacier. Measurements carried out inKarakoram in a 40 cm thick debris layer covering the Hinarche gla-cier show an analogous summer thermal regime at 17 cm of depth(Mayer et al., 2010).
The BTSmeasurements partly confirm the GSTmeasurement resultsin the areas outside the rock glacier. On the other hand, the samplingpoints located over the rock glacier provide quite different results,with generally warmer temperatures (Fig. 12). According to theBTS measurements, marginally-active permafrost and/or permafrostclose to melting point would exist on the rock glacier (Hoelzle et al.,1999; Gruber and Haeberli, 2009). However, given the dependenceof BTS temperatures on so many factors, and their high spatial vari-ability, which represent serious limitations for their interpretation(Delaloye, 2004; Lewkowicz and Ednie, 2004; Brenning et al., 2005),these results should be evaluated in connection with GST data and inlight of the other investigations that have been carried out in thestudy area.
Fig. 12. Location and temperatures of theBTSmeasurements carried out in 2009, 2010 and2011 (for interpretation of the references to color in this figure legend, the reader is re-ferred to the web version of the article).
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5.2. Subsurface ice
The GPR survey enabled the identification of a main reflector whichcan be interpreted as the bottomof a frozen bodywithin the CimaUomorock glacier (Fig. 9). Unlike previous studies which investigated similarrock glaciers in the Dolomites, no other reflectors could be identified inthe frozen core of the Cima Uomo rock glacier. Concave reflectors were
reported, for example, in the frozen core of theMurfreit and CrodaRossarock glaciers by Krainer et al. (2010, 2012), who interpreted them asintercalated layers of ice and debris, typical of the evolution from adebris-covered glacier. Curved and upward-dipping reflectors werealso observed in the Thabor and Sachette rock glaciers (Monnier et al.,2011, 2013), and were similarly interpreted as debris inclusions alongthrust planes in the ice, supporting the hypothesis of the glacial originof the massive ice body embedded in these rock glaciers. Likewise, a“nested spoons” internal structure, similar to that commonly observedin valley glaciers, was revealed by GPR investigations on a polar rockglacier by Fukui et al. (2008). The lack of distinct GPR structures insidethe frozen body of the Cima Uomo rock glacier prevents the clearidentification of its glacial origin, even if it is probable. The reducedpenetration of the GPR signal could also have played a role in preventingthe reconnaissance of internal structures.
The electrical resistivity measured within the Cima Uomo rockglacier is in the range indicated by Haeberli and Vonder Mühll (1996)for perennially frozen rock glacier material (5–500 kΩ m) and in thesame order of magnitude which was reported for congelation ice inthe ground, both interstitial and segregated (Kneisel, 2006; Hauck andKneisel, 2008) (Fig. 8). Resistivities between 10 and 100 kΩmgenerallyindicate the presence of frozen debris in rock glaciers, talus slopes andmoraines, whereas ice-rich sediments in rock glaciers are usually char-acterized by resistivities larger than 100 kΩ m (Leopold et al., 2011;Otto et al., 2012; Schneider et al., 2013). Higher values, ranging fromthousands of kΩ m to MΩ m, were reported for the frozen layers ofseveral rock glaciers (Maurer and Hauck, 2007), and extremely highvalues (N5 MΩ m) were also observed for massive ice bodies of likelyglacial origin embedded in rock glaciers (Ishikawa et al., 2001; Riboliniet al., 2007, 2010).
The direct association of the subsurface resistivity with a frozen orunfrozen status of the deposits, and the resulting delimitation of afrozen body, are not straightforward (Kneisel, 2006; Lambiel andPieracci, 2008). Theoretically, the resistivity of these deposits dependsupon the relative percentages of air, water, ice and rocks (Telfordet al., 1990; Hauck et al., 2011). However, the contribution of air andice is very similar (Kneisel, 2006) and the interpretation could be verydifficult without other geophysical or geological constrains, becausethe threshold between frozen and unfrozen sediments is strongly site-dependent.
In our study case the interpretation of the internal structure of therock glacier, and the identification of the possible ERT threshold valueof 80 kΩ m between frozen and unfrozen sediments, took advantagefrom the comparative analysis of the ERT and GPR surveys (Fig. 9).The two methods agree rather well in indicating the existence of afrozen body within the Cima Uomo rock glacier, in which the close cor-respondence between theMRRH and the layers characterized by abruptresistivity contrasts is observable (Fig. 9). According to the 80 kΩ mthreshold, frozen sediments should not be present in the lower part ofthe rock glacier (0–25 m along the ERT profile). However, according tothe other evidences (GST data and surface displacement) the presenceof frozen material in this part of the rock glacier cannot be completelyexcluded.
5.3. Current rock glacier kinematics
The creeping process affecting the Cima Uomo rock glacier is re-vealed by the presence of ridges and furrows on its surface andby its horizontal displacement. The rather low surface velocity(8–22 cm year−1) is comparable to velocities reported for “lowactive” rock glaciers in the Swiss Alps (Delaloye et al., 2010). Else-where in the Dolomites, surface velocities from b0.05 to 0.5 mwere measured on the Murfreit rock glacier (Krainer et al., 2012),and displacement rates in the same order of magnitude wereobserved on the Cadin di Croda Rossa and Cadin del Ghiacciaio rockglaciers (Krainer et al., 2010).
Fig. 13. Ground surface temperature regime from the GST measurement sites located in the Cima Uomo area (see Fig. 7b for location), compared with snow height and air temperaturerecorded at Passo Valles (2020 m a.s.l.).
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Close to the front (line H1–H6), the rock glacier showed lower dis-placement rates than on the middle (line H7–H11) and upper (lineH12–H14) parts (Fig. 11). The lower velocities correspond to thelower resistivities of all the ERT profile. Conversely, the higher surfacevelocities weremeasured above the high-resistive core, suggesting a re-lationship between the presence of the inner frozen material and the
Table 1Relevant parameters obtained from the GST data. MAGST: mean annual ground surface tempequilibrium temperature. WEqT values are given with standard deviation in order to substanti
2009–2010 201
Elevation( m a.s.l.)
Slope (°) MAGST (°C) GFI (°C·day) WEqT (°C) MA
U01 2410 9 0.3 −677 −4.5 (±0.17) 1.5U02 2416 2 0.8 −483 −3.0 (±0.14) 2.2U04 2431 10 0.7 −398 −2.7 (±0.11) 1.7U05 2436 34 0.9 −304 −2.4 (±0.13) 1.8U06 2483 16 1.2 −65 −0.3 (±0.04) 2.1U08 2475 32 0.3 −493 −3.2 (±0.17) 1.1U09 2497 13 −1.5 −542 −3.1 (±0.12) −1U10 2565 14 0.1 −150 −0.8 (±0.05) 1.3
Mean of all sites 0.3 −389 −2.5 1.3MAAT (°C) −1.8 −0
surface movement (Fig. 8), although a link with the slope cannot beexcluded.
The surface lowering observed at the sampled points (Fig. 11) is con-siderably higher than the vertical displacement expected at the surfaceof the rock glacier, which has a low slope (3 ± 0.5%). This suggests thatthere is an additional lowering of the surfacewhichmaybe attributed to
erature; MAAT: mean annual air temperature; GFI: ground freezing index; WEqT: winterate the stability and thus the strength of the mean temperature.
0–2011 2011–2012
GST (°C) GFI (°C·day) WEqT (°C) MAGST (°C) GFI (°C·day) WEqT (°C)
−439 −3.1 (±0.14) 0.8 −783 –
−211 −1.8 (±0.15) 1.8 −513 –
−280 −2.1 (±0.20) 1.0 −627 –
−159 −1.6 (±0.15) 0.8 −611 –
−19 −0.0 (±0.09) 1.9 −125 –
−412 −2.7 (±0.23) 1.0 −502 –
.2 −459 −2.7 (±0.14) −1.3 −565 –
−87 −0.5 (±0.05) 1.2 −260 –
−258 −1.8 0.9 −498 –
.4 0.1
Fig. 14.Alpine permafrost indexmap (APIM) of the study area. Themapwas processedwithin the alpine PermaNET project (Boeckli et al., 2012) and is freely available at http://www.geo.uzh.ch/microsite/cryodata/ (last accessed on 15 June, 2014) (for interpretation of the references to color in this figure legend, the reader is referred to the web version of the article).
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the melting of the ice core and/or to the settling of the active layerdebris. This finding may indicate that the debris layer covering the icebody embedded in the Cima Uomo rock glacier is thinner than themean depth of the active layer and that the frozen body undergoesmelting (Haeberli, 2000). These results seem to suggest that the rockglacier, similarly to the Cima Uomo Glacier, is subject to imbalancedconditions with the current climate of the area.
5.4. Genesis and evolution of the Cima Uomo composite landform
Several models have been proposed in the literature for describingthe genesis and the evolution of landforms resulting from the interac-tion between glaciers and rock glaciers in the Alps (Guglielmin et al.,2001; Ribolini et al., 2007;Monnier et al., 2011, 2013). The developmentof the Cima Uomo composite landform since the LIA can be tentativelyreconstructed considering suchmodels in associationwith our observa-tions and findings.
The Cima Uomo Glacier probably reached its maximum recentextent during the LIA, although it cannot be excluded that advances ofthe same magnitude may have occurred earlier in the Holocene(Ribolini et al., 2007). In this phase, the glacier deposited the two largelateral moraines, which clearly define its lateral limit (morphological
unit 3; Figs. 2b and 4b), and its terminus was approximately close tothe lower edge of the modern rock glacier, although the correct identi-fication of its lower boundary is uncertain. Morphological field observa-tions seem to suggest that this limit corresponds to the frontal morainelying at about 2400 m a.s.l.
During the LIA and at the beginning of the 20th century the lowerpart of the glacier was likely covered by debris, whereas the middleand the higher areas were mostly free of debris (DuÖAV, 1905;Castiglioni, 1925, Fig. 3). The long-lasting differential ablation thatoccurred during the post-LIA retreating phase might have led to thepreservation of the ice under the thick layer of debris in the lower partof the glacier, and to the strong thinning of the clean ice in the middlesector which, ultimately, underwent a complete melt. The large hollownow existing in the middle area (morphological unit 2; Fig. 4b and c)provides evidence of this process. Moreover, the existence of flutingground moraines in this zone suggests that the former basal ice was intemperate conditions (Haeberli, 2000).
The highest part of the former glacier probably survived thanks tomore favorable topo-climatic conditions, ensured by the steep rockwallsof the cirque, and to the increasing debris coverage (López-Morenoet al., 2006; Coleman et al., 2009; Carturan et al., 2013a). According tothe definition provided by Serrano et al. (2011), the present Cima
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Uomo debris-covered glacier (morphological unit 1, Fig. 4b) could bedefined as a “glacial ice patch,” i.e. a remnant of an old glacier that haslost mass to the point that its internal motion and flow have ceased, assuggested by the complete lack of crevasses. Ice patches no longerdisplay the characteristics of a glacier (i.e. mass transfer from theaccumulation area to the ablation area) and can be regarded as inactive.Our observations confirm that accumulation processes are currentlyabsent on the glacier and that the avalanche-fed snow patches whichsporadically form in snowy years (such as in 2009; Valt and Cianfarra,2009) completely melt in dry and/or warm years (e.g. the 2012summer; Carturan et al., 2013c). On the other hand, net ablation affectsthe entire surface of the ice body, as revealed by themarked lowering ofthe surface from 2003 to 2006 (Fig. 6).
The lower part of the former glacier started to develop independent-ly and progressively became a rock glacier-like featurewhich is current-ly preserving an ice body of possible glacial origin and is creeping underpermafrost conditions. A connection of the frozen body detected by ERTand GPR in the rock glacier to the upslope debris-covered glacier cannotbe excluded. However, the geomorphology of the in-between area (seeSection 2), and in particular the presence of fluting ground morainesand of stable debris, with no surface lowering or deformation between2003 and 2006, lead us to exclude the occurrence of subsurface ice inthis area, suggesting the complete separation of the two ice bodies.
Our findings seem to exclude alternative hypotheses for the genesisand development of the Cima Uomo rock glacier. Themodels presentedin Ribolini et al. (2007) and Serrano et al. (2010), for example, involvethe advance of a glacier during the LIA on the highest part (rootingarea) of a pre-existing rock glacier, which may have been partlydisrupted. The advancing glacier may have added ice to the rock glacier,which may have been subsequently incorporated into the debris bodyas a layer of high resistivity (i.e. sedimentary) ice. On the contrary, inour study case, the rock glacier seems to have developed after the LIA,from the former debris-covered tongue of the Cima Uomo Glacier. Themain element in support of this hypothesis is the presence of an intactfrontal moraine which displays morphological continuity with thelateral moraines and completely encloses the rock glacier. Althoughthe creeping rate of the lower edge of the rock glacier is unknown, themean cumulative displacement of the lower transverse profile shownin Fig. 11 (about 10 m in a century) suggests that it should not havebeen sufficient to allow the rock glacier to go over the LIA frontalmoraine.
6. Conclusions
Geomorphological, geophysical and topographic surveys, in associa-tionwith ground surface temperature measurements, were used for in-vestigating the evolution of a composite landform in the Dolomitessince the end of the LIA, and its current status. The present-day spatialdomain of glacial and periglacial processes was also assessed usingmulti-temporal differencing of high-resolution DEMs. The resultsshow that the glacier which built the impressivemorainic complex dur-ing the LIA has now retreated to the upper cirque, where thetopoclimatic conditions ensured by steep rockwalls and the completedebris cover enable its persistence. It is however inactive and reducedto a “glacial ice patch,”which lacks accumulation area andmass transferand undergoes mass loss and lowering over its entire surface.
Marginal permafrost conditions exist in the study site, and a creep-ing debris feature embedding a core of frozen material (i.e. a rockglacier) is developing in the area formerly occupied by the tongue ofthe glacier, which is now dominated by periglacial processes. Accordingto the geomorphological and geophysical evidences, the rock glacieri) seems to have developed from the former debris-covered tongue ofthe Cima Uomo Glacier, and ii) is currently completely enclosed by theLIA morainic complex. Alternative hypotheses proposed by previousstudies, which suggest the advance of glaciers during the LIA on therooting area of pre-existing rock glaciers, can probably be excluded.
Our study case provides new insights into the mechanisms involvedin the shift from glacial to periglacial geomorphic processes in highmountain areas, and the proposed evolutionmodel might be applicableto other sites where such a transition took place in response to the rapidenvironmental changes since the LIA.
Acknowledgements
This study was funded by the Italian MIUR project (PRIN 2010–2011)“Response of Morphoclimatic System Dynamics to Global Changes andRelated Geomorphological Hazards” (local and national coordinators G.Dalla Fontana and C. Baroni) and also supported by the Strategic Projectof the University of Padova “GEO-RISKS, Geological, Morphological andHydrological Processes: Monitoring, Modelling and Impact in theNorth-Eastern Italy” (head of the Research Unit: A. Carton). The workwas also conducted in the framework of an agreement among the Geo-logical Survey of the Autonomous Province of Trento, the Department ofGeosciences of the University of Padova, and the Department of Earthand Environmental Sciences of the University of Pavia for permafrostmonitoring in Trentino. Fieldwork was supported by the HelicoptersUnit of the Autonomous Province of Trento and was conducted withthe collaboration of S. Benigni, G. Degasperi, and M. Dall'Amico. Weacknowledge ARPAV Regione Veneto for providing climatic data andthe Autonomous Province of Trento for providing topographic data(orthophotos and DEMs). We also acknowledge A. Crepaz (ARPAV-Regione Veneto) who provided the picture of the study site (Fig. 2a).We are also very grateful to M. Meneghel (University of Padova), whofirst began and then encouraged our investigations on the landformpresented in this paper.
Appendix A. Supplementary data
Supplementary data associated with this article can be found in theonline version, at http://dx.doi.org/10.1016/j.geomorph.2014.08.025.These data include Google maps of the most important areas describedin this article.
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