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The hidden part of the cryosphere – Ice in caves

The hidden part of the cryosphere – Ice in caves

The cryosphere can be found in various places in many forms and shapes… in the atmosphere, on land and sea. A lesser known part of the cryosphere is hidden deep in the dark, in the cold-karstic areas of the planet: Ice caves! The ongoing climate change affecting ice all over the world is now rapidly melting these hidden ice masses as well. We therefore need to hurry up and try to collect as much information as we can before all will melt away…


The big melting

The ice masses around the globe, in ice sheets, sea ice, and mountain glaciers, have been melting away in past decades (see this previous post). The reduction of the cryosphere, both in terms of area and mass, has particularly been visible in the European Alps over the last 30 years. On the one hand, large and small Alpine glaciers decline, fragment and even disappear, and this trend has accelerated since the mid 1980s. Mountain glaciers are therefore considered to be sensitive indicators for climate variability. On the other hand, the warming climate is also acting on permafrost degradation, mostly affecting the stability of rock-slopes and cliffs.

What makes the international scientific community worry at the moment is how fast this abrupt glacial reduction is occurring globally. However, not all the natural environments respond in the same way to sudden changes in the climate system! Fortunately for us scientists, there are physical environments and ecological niches more resilient to external perturbations. This aspect has sometimes allowed the preservation of environments and information in the Earth’s climatic history that would have been otherwise destroyed.

Caves are resilient

Among the most resilient natural environments there are caves, “protected” by the rocky mass within which they were formed. In the mountains, high-altitude karst cavities can contain huge deposits of ice representing a lesser known part of the cryosphere. Speleologists face such ice in caves both as a joy and a damnation: fascinating by their beautiful shapes and morphologies, they also see it as an unwieldy presence that prevents explorations of still unknown voids in the alpine karstic systems.

Fig. 2: An ice deposit in a cave of the southeastern Alps [Credit: Renato R. Colucci].

 

But ice in caves is not just something beautiful (but isn’t it? Look at Fig. 2!). It rather represents a precious natural archive, sometimes with high temporal resolution, able to tell the climate history of large part of the Holocene (the last 11700 years of the Earth’s history). The permanent ice deposits, i.e. the ice staying longer than just a winter season, often defined in a colorful way as “fossil ice” by speleologists, is what counts the most. As it typically gets older than 2 years, which is one threshold for the general definition of permafrost, this phenomenon is part of the mountain permafrost… right or wrong, ice in caves is ground ice!

Fig. 3: Huge entrance of a cave opening in the Dachstein limestones of the Canin-Kanin massif, southeastern Alps [Credit: Renato R. Colucci].

 

Generally in the Alps such ice deposits lie in caves having their opening at altitudes above 1,000 m (Fig. 3), but locally even lower. The formation of these unique environments depends on a combination of geomorphological and climatic characteristics, which allow for accumulation and preservation of ice also in places where this would be very unlikely.

Now, although the caves are resilient environments, ice melting due to climate change is rapidly increasing there as well. This is why it is important to save as much information as possible from the remaining ice, before it is definitely lost!

The C3 project – Cave’s Cryosphere and Climate

The C3-Cave’s Cryosphere and Climate project is under the scientific guidance of the National Research Council (CNR) of Italy, and precisely the climate and paleoclimate research group of ISMAR Trieste. It aims to monitor and study ice deposits in caves. Such ice deposits store several information related to the paleoclimate, the biology, the chemistry and ecology of these environments.

Fig. 4: Drilling ice cores with the aim to extract the CCC layer from this ice body in a cave of the southeastern Alps [Credit: Arianna Peron].

The project started in 2016, following the discovery of a coarse cryogenic calcite deposit (CCCcoarse) in an ice layer (in-situ) in a cave of the Canin-Kanin massif, in the Julian Alps, located between Italy and Slovenia. This finding, representing the first evidence of CCC in the southern Alps, provides an important opportunity to understand the processes associated to the formation of these particular calcite crystals (Fig. 4). Previously, the CCC (Fig. 5) was only found on the floor in caves where ice had already melted away. What makes it interesting is the fact that it is possible to date these crystals using the isotopic ratio of some trace elements in radioactive materials, typically Uran and Thorium.

Fig. 5: Millimetric crystals of coarse cryogenic calcite found in-situ in the southern Alps [Credit: Renato R. Colucci].

The strongest financial and logistic support to the project is given by the Alpine Society of the Julian Alps through its speleological group, the E. Boegan Cave Commission. In addition to the CNR and other Italian institutions such as the University of Trieste, University of Bologna, Insubria University in Varese, Milano Bicocca University and the Natural Park of the Julian Prealps, the project involves research institutes and universities from Germany (Institute of Physics of Heidelberg University), Switzerland (Paul Scherrer Institut; Swiss Institute for Speleology and Karst Studies), Austria (Innsbruck University; Palynology and Archaeobotany Research Group), and Slovenia (Geological survey of Slovenia).

Many activities and several results already unveiled few of the secrets hidden in such environments: the realization of the first thermo-fluido-dynamic model in an ice cave, the development of innovative techniques for studying the mass balance of the ice, the study of the thermal characteristics of the rock and therefore of the permafrost and the active layer, the development of innovative and multidisciplinary methods of ice dating.

But there is little time to do all, and we must exploit it to the fullest!

Further reading

Edited by Clara Burgard


Renato R. Colucci works in the climate and paleoclimate research group of ISMAR-CNR, Department of Earth System Sciences and Environmental Technology. He is also adjunct Professor of glaciology at the University of Trieste (Italy). During his PhD he honed his skills in glacial and periglacial geomorphology at UNIS (University Center in Svalbard). His research centers around the interactions between cryosphere (glaciers, permafrost, ice caves) and the climate, spanning from the end of the Last Glacial Maximum to the present days.

Image of the Week – Alien-iced

Image of the Week – Alien-iced

What do Chile and Jupiter’s moon Europa have in common? If you like astronomy, you may reply “space missions!” – Chile’s dry air and clear skies make it an ideal location for telescopes like the VLT or ALMA, while Europa’s inferred subsurface ocean will be studied by the upcoming mission to Jupiter JUICE, due to launch in 2022. But Chile’s high altitude Atacama desert and Europa’s frozen surface also have another feature in common, as you can see in this Image of the Week: ice spikes!   


Penitentes is the word

The official name of these ice spikes is “Penitentes”, Spanish for penitents. Why? As you might see (with quite some imagination) on the Image of the Week, there is some resemblance with a kneeling and praying procession.

Fields of penitentes ranging from a few centimetres to five metres can be found above 4000 m altitude both in the Andes and Himalayas, the only places on Earth where the right conditions exist for their formation. Because although it looks as if the snow is just blown into penitentes by unidirectional winds, in reality everything is due to thermodynamics…

I promise I will not write the equations this time (see this previous post); instead, I invite you to read them in this paper. In summary, penitentes form where snow is in contact with very dry and very cold air. As the sun shines, the snow absorbs the energy and heats up from inside, so much and so fast that the only way to be rid of that heat is by changing phase, directly from solid to water vapour (this is called sublimation). Since snow is anything but a smooth surface, sun rays will in fact be more concentrated at given locations on the snow, so that sublimation occurs only at specific points. But it is a self-amplifying mechanism: sublimation will leave a little crater behind in the snow, whose shape will concentrate even more the sun rays and lead to further sublimation. And this is how the penitentes get their shape.

 

Penitentes and the Atacama Pathfinder EXperiment (APEX) telescope. Photo: Babak Tafreshi/ ESO

Where is the link with Europa?

Hopefully by now, you are happy because you have just learnt about yet another weird-but-wonderful cryospheric phenomenon on Earth. But, remember how the post was about about Europa in the beginning? This is because researchers have recently analysed data from the past mission to Jupiter Galileo that might suggest that the conditions are right on Europa for penitentes to exist. They had to use the careful phrasing because the data resolution was not good enough to see the actual individual penitentes and had instead to rely on their thermic signature.

As reported in the media storm of these last two weeks (see here, here or here for example), this is an important discovery for the planning of future space missions. Which landing site to use? Play it safe and land far from these ice blades, or go and study them but risk destroying your lander? Either way, we shall continue reporting about the cryosphere, from this world and beyond…

Reference/Further reading

 

Edited by Clara Burgard

Image of the Week – Inspiring Girls!

Image of the Week – Inspiring Girls!

What, you may ask, are this group of 22 women doing standing around a fire-pit and what does this have to do with the EGU Cryosphere blog? This group of scientists, artists, teachers, and coaches gathered 2 weeks ago in Switzerland to learn how to become instructors on an Inspiring Girls Expedition. But what, you may ask again, is an Inspiring Girls Expedition? Well read on to find out more…


What is an Inspiring Girls Expedition?

In 1999 Glaciologist Erin Petit, Geographer Michele Koppes, and 5 high-school girls hiked out onto the South Cascade Glacier in Washington State. For the next week, this motley crew spent their time camped out on a glacier moraine, exploring the landscape and performing scientific experiments by day, and talking and listening to each others thoughts and stories by night – that was the birth of Girls on Ice.

Over the next 13 years, more expeditions took place and more instructors (scientists, artists and mountain guides) started to get involved. In 2012, a second Girls on Ice expedition was born in Alaska and, in the years since, there have been Girls on Ice expeditions in 4 different locations and in 2 different languages! The idea has expanded to other areas of wilderness expedition as well, with new projects starting up: Girls on Rock, Girls in Icy Fjords and Girls on Water – nowadays these expedition are collectively known as Inspiring Girls Expeditions!

But I haven’t really answered the question – what is an Inspiring Girls Expedition? It is a wilderness and science education program for high-school aged girls. Over the course of around 12 days, these girls get the chance to explore a wilderness setting, learn about scientific thinking, increase self-confidence, and push their physical and intellectual boundaries as part of a single-gendered team. And, importantly – it’s FREE – opening it up to girls who might not have the financial means to do something like this otherwise. Everyone who goes on the expedition from scientists to mountain guides and instructors is female, making this expedition pretty unique! I think the philosophy of Inspiring Girls is best described by their mission statement:

Our mission is to bring out your natural curiosity, inspire your interest in science, connect the arts and sciences, free you from gender roles, provide a less competitive atmosphere, and encourage trust in your physical abilities.

The workshop

I’ve been following the work of Girls on Ice for a while, so when I saw a chance to go on an instructor training course, I enthusiastically signed up! Over 4 days in June 2018, a group of women from at least 8 different countries got together in a hiking hut in Switzerland for an Inspiring Girls Instructor Workshop, hosted by Swiss Girls on Ice. We came from a broad range of backgrounds: glaciologists, climate scientists, biologists, artists, architects, professional coaches, teachers (I hope I haven’t forgotten anyone!). We started off by learning more about the Inspiring Girls philosophy, what they expeditions aim to teach, and how they keep the girls safe and deal with any issues that might arise. Then came the thinking part for us…How do you teach in a wilderness setting? How to keep teenage girls engaged in what you are doing? What is a good leader? This gave us a lot of food for thought and we discussed a lot of these issues late into the evenings!

Then the fun part (although we all look rather serious in the pictures – below), working on ideas for new Inspiring Girls Expeditions (the current expeditions are often over-subscribed so there is certainly scope for more expeditions in more places) with the hope of inspiring more girls! So definitely watch this space for more expeditions coming to a mountain, cave or forest near you!

Figure 2: Workshop participants designing new Inspiring Girls Expeditions [Credit: Marijke Habermann]

It was a fantastic few days, with a fantastic bunch of women and I certainly came away feeling inspired myself!

I have to admit, this isn’t your usual Image of the Week blog post, however, I hope the relevance to scientists, science educators, and anyone else that follows the blog is clear! There is a need to show girls and young women that they have the potential to do what they want: be that a glaciologist, a mountain guide (both very much male dominated careers) or something entirely different! This type of expedition, in a single-gendered environment, is a very effective way to help build courage, confidence, and self-reliance!

This sounds cool – how can I get involved?

The team at Inspiring Girls are always looking for new people who are keen and enthusiastic about their project to get involved as volunteers, by donating a bit of cash or simply spreading the word about the expeditions – check their website to see how you can help out!

Edited by Clara Burgard

Image of the Week — Orange is the new white

Figure 1. True color composite of a Sentinel-2 image showing the dust plume off the coast of Libya on 22-Mar-2018 (see also on the ESA website) [Credit: processed by S. Gascoin]

On 22 March 2018, large amounts of Saharan dust were blown off the Libyan coast to be further deposited in the Mediterranean, turning the usually white snow-capped Mountains of Turkey, Romania and even Caucasus into Martian landscapes.  As many people were struck by this peculiar color of the snow, they started documenting this event on social media using the “#orangesnow hashtag”. Instagram and twitter are fun, but satellite remote sensing is more convenient to use to track the orange snow across mountain ranges. In this new image of the week, we explore dusty snow with the Sentinel-2 satellites…

Марс атакует ? #smurygins_family_trip

A post shared by Alina Smurygina (@sinyaya_ptiza) on


Sentinel-2: a great tool for observing dust deposition

Sentinel-2 is a satellite mission of the Copernicus programme and consists of two twin satellites (Sentinel-2A and 2B). Although the main application of Sentinel-2 is crop monitoring, it is also particularly well suited for characterizing the effect of dust deposition on the snowy mountains because:

  1. Sentinel-2A and 2B satellites provide high-resolution images with a pixel size of 10 m to 20 m (depending on the spectral band), which enables to detect dust on snow at the scale of hillslopes.
  2. Sentinel-2 has a high revisit capacity of 5 days which increases the probability to capture cloud-free  images shortly after the dust deposition.
  3. Sentinel-2 has many spectral bands in the visible and near infrared region of the light spectrum, making easy to separate the effect of dust on snow reflectance — i.e. the proportion of light reflected by snow — from other effects due to snow evolution. The dust particles mostly reduce snow reflectance in the visible, while coarsening of the snow by metamorphism (i.e. the change of microstructure due to transport of vapor at the micrometer scale) tends to reduce snow reflectance in the near infrared (Fig. 2).
  4. Sentinel-2 radiometric observations have high dynamic range and are accurate and well calibrated (in contrast to some trendy miniature satellites), hence they can be used to retrieve accurate surface dust concentration, provided that the influence of the atmosphere and the topography on surface reflectance are removed.

Figure 2: Diffuse reflectance for different types of snowpack. These spectra were computed with 10 nm resolution using the TARTES model (Libois et al, 2013) using the following parameters: snowpack density: 300 kg/m3, thickness: 2 m, fine snow specific surface area (SSA): 40 m2/kg, coarse snow SSA: 20 m2/kg, dust content: 100 μg/g. The optical properties of the dust are those of a sample of fine dust particles from Libya with a diameter of 2.5 μm or less (PM2.5) (Caponi et al, 2017). The Sentinel-2 spectral bands are indicated in grey. [Credit: S. Gascoin]

Dust on snow from Turkey to Spain

The region of Mount Artos in the Armenian Highlands (Turkey) was one of the first mountains to be imaged by Sentinel-2 after the dust event. Actually Sentinel-2 even captured the dust aloft on March 23, before its deposition (Fig. 3)

Figure 3: Time series of three Sentinel-2 images near Mount Artos in Turkey (true color composites of level 1C images, i.e. orthorectified products, without atmospheric correction). [Credit: Contains modified Copernicus Sentinel data, processed by S. Gascoin]

Later in April another storm from the Sahara brought large amounts of dust in southwestern Europe.

Figure 4: Sentinel-2 images of the Sierra Nevada in Spain (true color composites of level 1C images). [Credit: Contains modified Copernicus Sentinel data, processed by S. Gascoin]

This example in the spanish Sierra Nevada nicely illustrates the value of the Sentinel-2 mission since both images were captured only 5 days apart. The high resolution of Sentinel-2 is also important given the topographic variability of this mountain range. This is how it looks in MODIS images, having a 250 m resolution.

Figure 5: MODIS Terra (19) and Aqua (24) images of the Sierra Nevada in Spain. True Color composites of MODIS corrected reflectance. [Credit: NASA, processed by S. Gascoin]

Sentinel-2 satellites enable to track the small-scale variability of the dust concentration in surface snow, even at the scale of the ski runs as shown in Fig. 6.

Figure 6: Comparison of a true color Sentinel-2 image and a photograph of the Pradollano ski resort, Sierra Nevada. [Credit: photograph taken by J. Herrero / Contains modified Copernicus Sentinel data, processed by S. Gascoin]

A current limitation of Sentinel-2, however, is the relative shortness of the observation time series. Sentinel-2A was only launched in 2015 and Sentinel-2B in 2017. With three entire snow seasons, we can just start looking at interannual variability. An example in the Prokletije mountains in Albania is shown in Fig. 7.

Figure 7. Sentinel-2 images of the Prokletije mountains in Albania (true color composites of level 1C images) [Credit: Contains modified Copernicus Sentinel data, processed by S. Gascoin]

These images suggest that the dust event of March 2018 was not exceptional in this region, as 2016 also highlights a similar event. The Sentinel-2 archive will keep growing for many years since the EU Commission seems determined to support the continuity and development of Copernicus programme in the next decades. In the meantime to study the interannual variability the best option is to exploit the long-term records from other satellites like MODIS or Landsat.

Beyond the color of snow, the water resource

Dust on snow is important for water resource management since dust increases the amount of solar energy absorbed by the snowpack, thereby accelerating the melt. A recent study showed that dust controls springtime river flow in the Western USA (Painter et al, 2018).

“It almost doesn’t matter how warm the spring is, it really just matters how dark the snow is.”

said snow hydrologist Jeff Deems in an interview about this study in Science Magazine. Little is known about how this applies to Europe…

Further reading

 Edited by Sophie Berger


Simon Gascoin is a CNRS researcher at Centre d’Etudes Spatiales de la Biosphère (CESBIO), in Toulouse. He obtained a PhD in hydrology from Sorbonne University in Paris and did a postdoc on snow and glacier hydrology at the Centro de Estudios Avanzados en Zonas Áridas (CEAZA) in Chile. His research is now focusing on the application of satellite remote sensing to snow hydrology. He tweets here and blog here.

 

 

Marie Dumont is a researcher, leading the snow processes, observations and modelling research team at the snow study centre (CNRM/CEN, Grenoble, France). Her research focuses on snow evolution mostly in alpine region using numerical modelling and optical remote sensing.

 

 

 

Ghislain Picard is a lecturer working at the Institute of Geosciences and Environment at the University Grenoble Alpes, in the climate and ice-sheets research group. His research focuses on snow evolution in polar regions in the context of climate change. Optical and microwave remote sensing is one of its main tools.