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86 Proceedings of the 17th International Congress of Speleology
e Cenote Project: monitoring a high-altitude ice cave in the Dolomites, Italy
Tommaso Santagata1, Francesco Sauro1,2, Christoph Spötl3, Daniela Festi4, Klaus Oeggl4, Luca Dal
Molin5, Farouk Kadded6, Marco Camorani7, Alessio Romeo1
Aliation: 1La Venta Esplorazioni Geograche, Via Priamo Tron 35/F -31100 Treviso
2Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Istituto Italiano di Speleologia,
Via Zamboni 67 – 40126 Bologna (Italia);
3Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria.
4Institute of Botany, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria
5Club Speleologico Proteo, Vicenza
6Leica Geosystems France, Paris.
Abstract
e Conturines Abyss, known also as “Cenote Abyss”, represents one of the deepest and most voluminous caves of the Dolomites.
is 280 m deep cave is characterised by a huge ice deposit, which makes it of primary interest for the study of palaeoclimate and
modern climate change in this region of the Alps. e cave was discovered in 1994 aer the abrupt emptying of a lake at 2940 m
a.s.l. in the Natural Park of Fanes, Sennes and Braies.
In 2015, a research project started to monitor long-term movements and volume changes of this ice deposit as well as to understand
the cave microclimate and the potential for future palaeoclimate research. With two expeditions organised in October 2015 and
September 2016, a complete survey of the cave was performed using laser scanning equipment (a Leica HDS7000 in 2015 and
a Leica P40 in 2016). e installation of barometric, temperature and humidity dataloggers in dierent areas of the cave have
provided a one-year record of the microclimate. In addition, pollen traps have been installed to study the present ux of pollen at
the surface and inside the cave, while preliminary analyses on pollen grains preserved in the ice are being carried out.
e Cenote ice cave research project aims to shed light on the climate evolution of the Dolomites during the last hundreds or
possibly thousands of years, as well as on the more recent environmental changes that led to the upward melting of the cave glacier.
Keywords:
1. Introduction
e Cenote Abyss represents one of the deepest and most
voluminous caves of the Dolomites. e cave is characterised
by a huge ice deposit for the rst 150 metres, which makes this
cavity of primary interest for the study of palaeoclimate and
modern climate change in this region of the Alps.
Speleological exploration started in 1994 with the abrupt
emptying of a small lake (labelled on the maps as “Lago delle
due Forcelle”) at 2940 m a.s.l. in the Natural Park of Fanes,
Sennes and Braies (Fig. 1a-b). Italian speleologists from the
caving club “Proteo” (Vicenza) noticed the presence of a cavity
in the ice at the bottom of the emptied doline and started the
exploration during the summer season. However, aer sev-
eral expeditions it was impossible to proceed beyond a depth
70 m inside the ice due to the dicult hydrological condi-
tions caused by the ice meltwater feeding an underground
stream. In the following years the cave passage inside the ice
deposit was again closed by winter snow accumulation, or the
stream entering the shas in summer was too dangerous to
permit new explorations. Only in 2010, a new expedition took
advantage of the low autumn temperature (below zero during
the night) to descend into the cave in dry conditions and to
explore a huge 160 m deep sha present below the main ice
mass. e exploration ended in a wide chamber (Baratro
Paolo Verico) whose oor is characterised by an impressive
rock glacier with signs of recent movement due to ice recharge
from above (Fig. 1c). e cave was surveyed down to a depth
of 285 m.
Aer this expedition the cave was again inaccessible due to
snow accumulation during the following four years, until the
passage was found open in the summer of 2015. e dimen-
sion and peculiar morphology of the cave ice deposits and
their position and altitude led to the idea of a long-term
research project to monitor movements and volume changes
of the ice as well as to understand the cave microclimate and
to explore the potential for future palaeoclimate studies. Two
expeditions, in 2015 and 2016, were organised mainly to
acquire scientic data, installing pollen traps, microclimate
loggers (humidity and temperature) in dierent points of the
cave and to perform a 3D scan of the whole cave. e data
Figure 1. Fig. 1. A) e Lake of two Fork in the year 1994 few
months before its sudden emptying; person on the top centre for scale
(photo C.S. Proteo). B) e entrance depression aer draining of the
lake in late August 1994 (photo C.S. Proteo). C) e giant chamber
Paolo Verico at the bottom of the 160 m deep sha during the laser
scanning operations in 2015. e oor is composed of a mixture of ice
and rock fragments, while a glacier tongue is hanging 130 m above
this huge chamber .
Proceedings of the 17th International Congress of Speleology 87
acquired until now are the base for a long-term monitoring
of the cave in order to understand the evolution of cave ice
deposits in this region of the Alps.
2. Geological settings and cave description
Located in the South Tirol region about 3 km east of the
village of San Cassiano in Badia, Piz of les Conturines (also
known as Piz of Two Forks), with its summit at 3064 m a.s.l.,
is the highest peak of the Conturines group.
e area of the Cenote cave is characterised by a wide syncline
structure comprising sedimentary rocks ranging from the
Upper Triassic to the Lower Miocene and mainly composed
of a succession of dolomite layers, whith a total thickness of 1
km (Sauro et al., 1995). ese sediments are overlain by other
formations such as the Dachstein Limestones (Uppermost
Triassic) of about 300 m thickness and the Grey Limestone
(Early Jurassic, Liassic), which is the most interesting Forma-
tion from a speleological point of view (Marchetto, 2007).
e cave starts with a karst depression (the original lake
“delle due forcelle”), about 20 m deep and 50x30 m wide. e
bottom of this doline is occupied by an ice and snow cone,
characterised by elongated fractures parallel to the depres-
sion’s major axis. Depending on the height of the snow cone, it
is sometimes possible to enter a chamber on its SW side in late
summer with a oor of transparent ice. On one side of this
room it is possible to descend down a channel carved between
the ice deposit and the rock wall. is conduit is characterised
by strong air current (breathing in summer and blowing in
winter), with the ice walls sculptured with 1 m wide melting
niches. From there it is possible to descend down a series of
shas developed at both the rock wall-ice contact and com-
pletely inside the ice mass. At a depth of 70 m the cave extends
completely within the ice inside a tunnel carved by the airow
(the wind tunnel, Fig. 2). e cave then descends 30 m via
another sha opening in a long NW-SE-oriented passage that
progressively opens into a large underground room. From
this point onward the descent is along the ice deposit and the
rock wall with the rst ending aer about 60 m with a huge ice
tongue suspended above the nal chamber. e free-hanging
depth of this deep chasm is 165 m (Baratro Paolo Verico). e
chamber at the bottom is 130 m long and about 40 m wide,
progressively descending to the lowest point of the cave with a
cone composed of a mixture of ice, sands and boulders.
Since the rst exploration in 1994, although the ice deposit
has slowly evolved, but the airow paths do not appear to have
changed substantially. Air currents opened tunnels in the ice
mass, with cupolas and melting niches, suggesting a potential
connection with cavities and fractures at the base of the exter-
nal ridge walls of San Cassiano.
3. Scientic objectives
3.1. Monitoring ice evolution through laser scanning
One of the main objectives of the two expeditions was to real-
ise a complete 3-dimensional survey of the nal chamber and
the ice deposit in order to acquire detailed data about volume
and sizes of this important underground palaeoclimate
resource of the Dolomites, and to obtain a quantitative record
of the cave glacier. Using a laser scanner to survey large and
complex subsurface environments such as the Cenote Abyss
allows rapid acquisition of high-precision data.
Because of its high altitude and the dicult access, a helicop-
ter was used to transport most of the gear and participants to
the site. Inside the cave, laser scanners and other necessary
tools were transported attached to the cavers’ harnesses to the
depth of -285 m.
e instrument used in 2015 was a Leica HDS 7000, a phase
dierence laser scanner equipped with a dual axis compen-
sator, on board control, a wavelength of 1.5 microns, laser
“CLASS 1” with a ow rate of 187 m and a resolution of 0.3
mm.
During the operations inside the cave, circular targets with a
magnetised support base rotating over 360° were used to have
easily identiable connection points between the scans. e
giant chamber at the bottom of the sha was surveyed using
11 scans at resolution of 12 mm. One scanning station was
located on an articial platform installed on the wall of the
sha at 110 m above the oor. is station enabled to map
in detail the lower side of the hanging ice glacier. In 2016,
the scan continued in the upper part of the sha (over the
ice tongue, and through the series of short shas and tunnels
carved between rock and ice up to the doline entrance).
is survey provides the detailed volume of the chamber
(420,000 m3), the rst record of a rock glacier at the base, as
well as the presence of an over 100 m thick ice deposit in the
upper part of the cave.
In 2016 we used a Leica P40 model, a time-of-ight laser
scanner enhanced by Waveform Digitising (WFD) technol-
ogy with a scan rate of up to 1 milion points per second and a
ow range from 0.4 m to 270 m.
e aim of the 2016 expedition was to detect the upper part of
the cave to a depth of about -140 m in order to connect with
the survey executed in 2015 and obtain a three-dimensional
model of the cave (Fig. 3a). Scanning operations with this
instrument have been also used inside the ice tunnel, provid-
ing the detailed shape of this important part of the cave with a
resolution of less than one centimeter.
Figure 2. e wind tunnel at 70 m of depth is completely carved
into the ice and is characterized by strong airow during summer
(Photo A. Romeo/Inside the Glaciers).
88 Proceedings of the 17th International Congress of Speleology
is high-precision 3D model will be the base for future mon-
itoring of the long-term evolution of the ice masses inside this
cave.
3.2. Microclimate monitoring
During the rst expedition in 2015, temperature and humid-
ity dataloggers were installed in three points of the cave in
order to study the microclimate during the year and to cor-
relate them with ice-volume variations in the cave (Fig. 3b).
e dataloggers were positioned at the following sites:
1. At the bottom of the entrance depression close to the rst
conduits carved in the ice by air ow (barometric, tem-
perature, humidity logger)
2. At the end of the wind tunnel, hanging over the following
30 m deep sha (temperature)
3. At the beginning of the rock glacier tongue on the oor of
Baratro Paolo Verico (temperature, humidity logger)
In 2016 the data were downloaded from the loggers. ese
preliminary data obtained in this rst year were compared to
temperature variations at the Rossalm weather station (15 km
from the cave entrance, 2340 m a.s.l) (Fig. 4). Seasonal tem-
perature uctuations at the bottom of the nal chamber are
between 0 to 0.05 °C in the winter season (from November to
May) and rise to 0.2 °C in summer. is delicate equilibrium
is controlled mainly by air currents: from March to Decem-
ber at the wind tunnel temperature changes are triggered by
external uctuations (between -1.4 and 0.4 °C) while during
the winter season from January to March the temperature
is stable around 0 °C. is stabilization is probably related
to periods of closure of the main cave entrance or of other
unknown lower entrances by snow, blocking the air currents.
It is therefore clear that climatic conditions at the surface
(seasonal mean temperatures and winter snow accumulation)
have a direct impact on the melting rate of the cave glacier up
to considerable depths. It is probable that the opening of the
passage through the ice with the emptying of the lake in 1994
has started an irreversible process of warming of the cave
environment resulting in considerable volumes of ice melt-
ing year by year. e preliminary data show that microclimate
monitoring of the cave provides robust information that can
be compared to quantitative loss of ice in the future due to the
volumetric record obtained with the laser scan high-precision
3D model.
3.3. Pollen traps and pollen analysis of ice samples
During the two expeditions pollen traps were installed at
dierent locations to assess the ux of pollen into the cave.
ese traps are composed of a container with a micrometric
mesh collecting microparticles from the air. e traps were
positioned in the same place as the sensors, and the entrance
tunnel and the wind tunnel are strategical for this study test,
because of the strong winds blowing from the outside during
the summer season. e ongoing study will provide an aver-
age of total pollen amount trapped by the cave and potentially
recorded in the ice deposits. A few ice samples were also col-
lected inside the wind tunnel in order to obtain preliminary
data on the pollen content of the ice.
4. Conclusions
e expeditions of 2015 and 2016 are the rst steps of a long-
term monitoring project that could provide interesting data
about the past conditions of the cave ice masses and of their
evolution in response to climate change. In this rst phase of
the project the main objective to record a high-denition 3D
model of the volumetric and morphologic conditions of the
ice deposits inside the cave, coupled with an ongoing moni-
toring of cave microclimate was achieved. In addition, pre-
liminary pollen data could open the prospective for the study
of the ice layers as palaeoclimate archive.
However, the research activities in this cave hinge on the
ability of being able to enter the cave in late summer/early
autumn, and to the weather conditions, requiring complex
and expensive logistics. Nonetheless, a new expedition is
planned for 2018 or 2019 in order to repeat the laser scans and
compare ice volume losses, in correlation with the climatic
conditions recorded at the surface.
References
Marchetto GC. (2007): “Speleologic researches in the Natural
Parks of Fanes-Sennes-Braies and Dolomiti d’Ampezzo
(Italy)”. In: Untertage Alpine 2007, Ramsau bei Berchtes-
gaden, 9-11 November 2007, 64-66.
Sauro U., Meneghel M., Bini A., Mietto P., Siorpaes C.
(1995): Altopiani Ampezzani. Geologia geomorfologia speleo-
logia. La Graca Editrice, 156 pp.
Figure 3. A) Projection of the laser scan 3D model of the Cenote
Abyss. B) Vertical section of the Cenote Abyss showing the location of
the data loggers and pollen traps.
Figure 4. Temperature curves of dierent stations in the cave and
the Rossalm weather station, from early October 2015 to the end of
September 2016.
