Ice Alive: Uncovering the secrets of Earth’s Ice

In collaboration with Rolex Awards for Enterprise, Proudfoot Media and I have produced a documentary film explaining the latest research into the surprising hidden biology shaping Earth’s ice. The story is told by young UK Arctic scientists with contributions from guests including astronaut Chris Hadfield and biologist Jim Al-Khalili. We went to great lengths to make this a visually striking film that we hope is a pleasure to watch and communicates the otherwordly beauty and incredible complexity of the Arctic glacial landscape. We aim to educate, entertain and inspire others into exploring and protecting this most sensitive part of our planet in their own ways.

We think the film is equally suited to the general public as school and university students, and we are delighted to make this a free-to-all teaching resource. Please watch, share and use!


Ice Alive: An audiovisual exploration of the Greenland Ice Sheet


Click through to the Vimeo page to watch full screen and full resolution!

As an Arctic scientist I am privileged to be able to explore the coldest parts of our planet, making observations and measurements and helping others to understand how these areas function by writing papers and giving talks, lectures and writing for magazines and newspapers. But to truly understand an environment, we must also explore the intangible and immeasurable. To communicate it to diverse audiences, we must use not only facts and observations, but aesthetics and emotion. The piece above is a bridge connecting music and science – an effort to understand and communicate the hidden beauty, complexity and sensitivity of the Greenland Ice Sheet through sound. I hope that projects like this will bring new audiences to Arctic science, using music, art and aesthetics to pique their curiosity.

This project arose from a chance encounter in 2017. I was a guest on Radio 4’s Midweek program, along with musician Hannah Peel. As I listened to her explain her art on air, and later listening to her music, especially the new album, ‘Mary Casio’, I was struck by the depth of thought and analysis underpinning her work. I reached out to see if she would be interested in applying the same process to exploring the changing Arctic.

To my surprise and delight, Hannah agreed to make a new composition. We chatted about Arctic science – ice sheet dynamics, albedo feedbacks and microbiology in particular, and I provided footage and images from our field sites in Greenland and Svalbard. Hannah then went away and composed a piece of music inspired by the intricate processes, nested feedbacks and hidden complexity of this environment. I then cut the music to drone footage I filmed on site in 2017. I am overjoyed with the result, because I think Hannah’s music communicates perfectly the almost paradoxical sense of grandeur and intricacy, power and vulnerability of the ice.

Explore more of Hannah’s amazing music here

Gradconsult MicroGrants 2018

Sheffield SME ‘Gradconsult’ have just opened their second annual Microgrant scheme. It is open for applications from early career researchers in any discipline based anywhere in the UK.


This could be a great way to get the ball rolling with grant capture and could support travel, consumables, logistics, science communication, etc. It’s a very open and flexible scheme with the focus being on funding individuals with passion and purpose who will make the most of every penny and benefit from getting ‘on the ladder’ with research funding.

The application deadline is 31st March and further details can be found here


Managing & Publishing Research Code

Several journals now request data and/or code to be made openly available in a permanent repository accessible via a digital object identifier (doi), which is – in my opinion – generally a really good thing. However, there are associated challenges. First, because the expectation that code and data are made openly available is quite new (still nowhere near ubiquitous), many authors do not know of an appropriate workflow for managing and publishing their code. If code and data has been developed on a local machine, there is work involved in making sure the same code works when transferred to another computer where paths, dependencies and software setup may differ, and providing documentation. Neglecting this is usually no barrier to publication, so there has traditionally been little incentive to put time and effort into it. Many have mad great efforts to provide code to others via ftp sites, personal webpages or over email by request. However, this relies on those researchers maintaining their sites and responding to requests.

I thought I would share some of my experiences with curating and publishing research code using Git, because actually it is really easy and feeds back into better code development too. The ethical and pragmatic arguments in favour of adopting a proper version control system and publishing open code are clear – it enables collaborative coding, it is safer, more tractable and transparent. However, the workflow isn’t always easy to decipher to begin with. Hopefully this post will help a few people to get off the ground…

Version Control:

Version control is a way to manage code in active development. It is a way to avoid having hundreds of files with names like “model_code_for” in a folder on a computer, and a way to avoid confusion copying between machines and users. The basic idea is that the user has an online (‘remote’) repository that acts as a master where the up-to-date code is held, along with a historical log of previous versions. This remote repository is cloned on the user’s machine (‘local’ repository). The user then works on code in their local repository and the version control software  (VCS) syncs the two. This can happen with many local repositories all linked to one remote repository, either to enable one user to sync across different machines or to have many users working on the same code.

Changes made to code in a local repository are called ‘modifications’. If the user is happy with the modifications, they can be ‘staged’. Staging adds a flag to the modified code, telling the VCS that the code should be considered as a new version to eventually add to the remote repository. Once the user has staged some code, the changes must be ‘committed’. Committing is saving the staged modifications safely in the local repository. Since the local repository is synced to the remote repository by the VCS, I think of making a commit as “committing to update the remote repository later”. Each time the user ‘commits’ they also submit a ‘commit message’ which details the modifications and the reasons they were made. Importantly, a commit is only a local change. Staging and committing modifications can be done offline – to actually send the changes to the remote repository the user ‘pushes’ it.

Adapted from

Sometimes the user might want to try out a new idea or change without endangering the main code. This can be achieved by ‘branching’ the repository. This creates a new workflow that is joined to the main ‘master’ code but kept separate so the master code is not updated by commits to the new branch. These branches can later be ‘merged’ back onto the master branch if the experiments on the branch were successful.

These simple operations keep code easy to manage and tractable. Many people can work on a piece of code, see changes made by others and, assuming the group is pushing to the remote repository regularly, be confident they are working on the latest version. New users can ‘clone’ the existing remote repository, meaning they create a local version and can then push changes up into the main code from their own machine. If a local repository is lagging behind the remote repository, local changes cannot be pushed until the user pulls the changes down from the remote repository, then pushes their new commits. This enables the VCS and the users to keep track of changes.


To make the code useable for others outside of a research group, a good README should be included in the repository, which is a clear and comprehensive explanation of the concept behind the code, the choices made in developing it and a clear description of how to use and modify it. This is also where any permissions or restrictions on usage should be communicated, and any citation or author contact information. Data accompanying the code can also be pushed to the remote repository to ensure that when someone clones it, they receive everything they need to use the code.


One great thing about Git is that almost all operations are local – if you are unable to connect to the internet you can still work with version control in Git, including making commits, and then push the changes up to the remote repository later. This is one of many reasons why Git is the most popular VCS. The name refers to the tool used to manage changes to code, whereas Github is an online hosting service for Git repositories. With Git, versions are saved as snapshots of the repository at the time of a commit. In contrast, many other VCSs log changes to files.

There are many other nuances and features that are very useful for collaborative research coding, but these basic concepts are sufficient for getting up and running. It is also worth mentioning BitBucket too – many research groups use this platform instead of GitHub because repositories can be kept private without subscribing to a payment plan, whereas Github repositories are public unless paid for.

Publishing Code

To publish code, a version of the entire repository should be made immutable and separate from the active repository, so that readers and reviewers can always see the precise code that was used to support a particular paper. This is achieved by minting a doi (digital object identifier) for a repository that exists in GitHub. This requires exporting to a service such as Zenodo.

Zenodo will make a copy of the repository and mint a doi for it. This doi can then be provided to a journal and will always link to that snapshot of the repository. This means the users can continue to push changes and branch the original repository, safe in the knowledge the published version is safe and available. This is a great way to make research code transparent and permanent, and it means other users can access and use it, and the authors can forget about managing files for old papers on their machines and hard drives and providing their code and data over email ‘by request’. It also means the authors are not responsible for maintaining a repository indefinitely post-publication, as all the relevant code is safely stored at the doi, even if the repository is closed down.

La Recherche Article: The microbes accelerating glacier melting

I recently published an article in French pop-sci magazine La Recherche about the wondrous microbial ecosystems on glaciers and ice sheets (here for French speakers). For those English speakers who do not subscribe to la Recherche, here is a translation.

Also, I strongly recommend the excellent translator who worked on this article with me – contact me if you need translation services and I can link you up.

The microbes accelerating glacier melting


Our planet is getting warmer and losing its ice. Mountain glaciers are disappearing and the great Greenland and Antarctic ice sheets are shrinking. These masses of ice are giant coolers for the planet and they reflect energy from the Sun back out into space, meaning the smaller they become, the more the planet warms. Surprisingly, the process of melting the vast glaciers and ice sheets is accelerated by microscopic life.

Glacier and ice sheet melting depends upon more than just temperature. Most of the energy driving melt comes from sunlight that hits the ice surface. Dirtier, darker ice absorbs more solar energy than clean, bright ice meaning more energy is available to drive melting. On the Greenland Ice Sheet in particular, the ice becomes very dark in the summer, with large areas reflecting just 20-30% of the sunlight hitting them. This is not a new phenomenon – in fact it was noticed by explorers during the great polar expeditions of the late 1800s. Intrigued, they examined samples of ice under their microscopes. The dark colour of the ice was not simply due to dust as they expected – astonishingly, the ice was stained by life (Nordenskjold, 1875). The ice surface is a patchwork of greys, reds and purples coloured by the collective effect of countless microscopic organisms, with potential knock-on effects for Earth’s climate (Uetake et al., 2010; Takeuchi et al., 2006; Yallop et al., 2012; Cook et al., 2017).

The dark sediment visible in the 1mx1m quadrat in this picture from the Greenland ice sheet is largely surface algae, along with some mineral grains. This is a particularly heavy patch, sometimes it cannot be seen with the naked eye, but occurred ubiquitously in our numerous study sites.

Microbes on Ice

When explorer Adolf E Nordenskjold arrived on the Greenland Ice Sheet in 1870 he immediately noticed the dark grey-purple colour of the ice. His colleague, a biologist called Berggren, examined the ice under the microscope and discovered a rich variety of microbial life. The importance of their discovery was clear to them – this life darkens the ice and increases its melt rate. Nordenskjold even suggested that the microbial life was the “greatest enemy of the mass of ice” and an accelerator of deglaciation at the global scale (Nordenskjold, 1875)!

Until recently, Nordenskjold’s observations of life on ice have remained obscure footnotes in the history of Polar exploration; however, as climate science has become increasingly urgent in the twenty-first century, Nordenskjold’s work has gained new significance. Contemporary scientists have confirmed the presence of a microbial ecosystem growing on the surface of the Greenland Ice Sheet and elsewhere and are now attempting to quantify their ice-darkening effect. Although it is an extreme environment where temperatures are low and nutrients scarce, there is abundant sunlight and liquid water to support photosynthesis, meaning microalgae can grow on the ice surface (Uetake et al., 2010; Yallop et al., 2012). The days are long in the Arctic in summer, with the sun staying above the horizon for twenty-four hours per day for part of the season, exposing the algae to intense and prolonged solar energy. This powers photosynthesis but over time the exposure stresses the ice algae, causing them to produce biological sunscreen molecules to protect their delicate photosynthetic machinery. These ‘carotenoids’ colour their cells very dark purple and enhance the biological darkening of the ice surface.

At the same time, the ice surface is peppered with holes that are often cylindrical but can have complex and irregular shapes (Cook et al., 2015). These holes range from centimeters to meters in diameter and depth and contain mixtures of biological and nonbiological material bundled up into small balls that sit on the hole floors. Nordenskjold first noticed these holes on the Greenland Ice Sheet and named them ‘cryoconite holes’, from the Greek for ‘holes with frozen dust’. These holes are the most biodiverse microbial habitat on Earth’s ice. They form when dust and debris becomes tangled up by long, thread-like cyanobacteria. The cyanobacteria are photosynthetic and as they grow they exude polymers that act as biological glues, binding the bundles of material together into stable granules. This biological bundling and binding of material creates a microhabitat for other microbes, especially those that can feed on molecules produced by the photosynthesizing cyanobacteria. As the granules grow they become heavier, meaning they settle on the ice surface. The biological material makes them especially dark, so the ice underneath melts quickly, causing holes to form in the ice surface with the granules sitting on the hole floor. The holes provide protection from the weather and intense sunlight and also prevent the microbes from being washed away. The cyanobacteria therefore sculpt the ice surface and engineer a comfortable, stable habitat where diverse microbial life can thrive in this extreme environment.

Cryoconite holes are more than icy buckets that hold microbial life. They are more like microbial mini-cities on ice, with each connected to many others by meltwater flowing between ice crystals just under the ice surface. Cryoconite microbes engage in engineering and construction, production, consumption, competition, predation, growth, reproduction, death, decay, immigration and emigration. There is both import and export of nutrients, waste and other biological material. At the same time, the hole itself changes its shape and size in response to changing environmental conditions with the emergent effect of maintaining the light intensity at the hole floor, promoting photosynthesis (Cook et al., 2010). Algal blooms and cryoconite are crucial components of the wider Arctic ecosystem, acting as stores of carbon (which they draw down from the atmosphere and fix into organic molecules), nutrients and biomass which can all be delivered to soils, rivers and oceans as glaciers melt (Stibal et al., 2012). Truly, these are widely interconnected complex adaptive systems created biologically on Earth’s ice.

The beautiful cryoconite at S6, Greenland ice sheet

The Cutting Edge of Life on Ice

While life on ice has been known for many years, most of the literature on the subject has been produced during the twenty-first century. Modern molecular biological techniques have enabled scientists to catalogue the species present in cryoconite and algal blooms, and modern instruments can measure their darkening effect. However, there are several major gaps in our understanding of life on ice. To quantify their effect on ice darkening worldwide, we need a reliable method to map icy microbes at the scale of entire ice sheets. From a biological perspective, we know which organisms live in algal blooms and cryoconite so we must now concentrate on determining how they function and what ecosystem services they might provide that could impact human society.

To estimate the total coverage of life on ice, we must detect it without actually being present to take samples. It is relatively easy to take samples and analyse them in a laboratory to tell if life is present, but doing the same from the air is a different problem. In addition to biological darkening, soots and mineral dusts colour the ice. Also, as the ice melts the crystals change shape and melt water can fill the spaces between them, which in itself changes the way the ice absorbs and reflects solar energy. Disentangling the biological signal from these other darkening processes has proven to be challenging.

However, because the darkening of ice by living cells is due to biological molecules that absorb light at specific wavelengths, we may be able to use the spectrum of reflected light to identify them. Chlorophyll, for example, absorbs red and blue light much more effectively than it absorbs green light (which is why we see leaves as green). For other biological molecules, the peak absorption will be at slightly different wavelengths, and non-biological materials will have their own absorption patterns too. However, while identifying ‘signature spectra’ is simple when only one material is present, it is much more difficult when several species with different light absorbing properties are mixed with non-biological materials. All of the light absorbers can be scattered unevenly and mixed vertically within the volume of ice which can itself be a complex aggregate of variously sized ice crystals and liquid water. The reflected light is a tangle of signals that can be hard to unpick.

At our laboratory at the University of Sheffield, we are working on a purpose-built drone which will fly back and forth over a patch of the Greenland Ice Sheet taking images at specific wavelengths of light. By analysing these images we hope to be able to produce a map of life on ice. Using the drone means we can follow the flight on foot and take ground samples to examine in the laboratory, enabling us to link the drone images to actual concentrations of different light absorbers on the ground. The wavelengths imaged by the drone match up with those measured by several Earth observation satellites, meaning that achieving life-detection using a drone should then enable the same from space.

The Rolex Awards for Enterprise Joseph Cook, 2016  Laureate
UAV flights in Svalbard (ph. Marc Latzel/Rolex)

As well as knowing where the life is, we also need a deeper understanding of how it functions. Recognition of ice surfaces as microbial habitats came at the same time as an explosion in accessible and affordable techniques in field molecular microbial ecology, meaning several groups have used high-throughput sequencing of marker-genes to identify the particular microbes present within cryoconite communities (e.g. Cameron et al., 2012; Edwards et al., 2014; Stibal et al., 2014, 2015). Environmental genomic techniques have also been used to investigate the total genetic composition of cryoconite communities (Edwards et al., 2013). To date, these have been snapshot studies, but in the very near future great insights into the functioning of cryoconite microbes will come from rapid metagenomic, metabolomic and metatranscriptomic studies. It has been suggested that ice surface microbes might be good targets for bioprospecting. Since they are able to thrive in conditions of low temperature, high light and low nutrients, they may well utilize survival strategies that we can exploit, either by extracting novel genes and biomolecules, or by observing and gaining ecological knowledge. Cryoconite has been suggested to be a potential source of antifreeze proteins, novel antibiotics and cold-active enzymes. The shape, illumination conditions and flushing with flowing meltwater make cryoconite holes natural analogs to industrial bioreactors which are commonly used to synthesise valuable biomolecules (Cook et al., 2015).

Deep insights will come from combining the expertise of microbial ecologists with glaciologists and physicists who, together, will link processes operating at the molecular level with changes in ice surface colour and patterns of melt, which suggests insights into the ecology of ice surfaces might one day be obtainable from the sky or from space. While this is some way off, great insights could be gained from a shift towards a holistic understanding of the ice surface as a ‘living landscape’.

Extraterrestrial Ice

We are working hard to achieve remote detection of life on ice for the purposes of mapping biological ice darkening from satellites and improving our ability to predict future ice melt. However, there is another potential outcome from this work… what if instead of looking down from space at our own planet, we turn the sensors around and start looking out?

The Greenland Ice Sheet is, in many ways, a good place for developing life detection technologies that can be applied to the search for life on other icy planets and moons. Take, for example, Europa. A recently funded NASA project will examine this icy moon of Jupiter for signs of life because of its potentially habitable icy shell and subsurface ocean. On Europa, the icy surface is sunlit and seeded with possibly mineral-rich snow that forms when liquid water in its subsurface oceans escapes via huge geysers (Hand et al., 2017). There is therefore a potentially dusty ice surface illuminated by sunlight that could support photosynthesis, just like the Greenland Ice Sheet (although the solar energy flux and temperature is lower on Europa and photosynthesis is highly unlikely). Any life detection technology that works on the Greenland Ice Sheet will have to overcome the challenges of ice optics, interference by mineral dusts and uncertain biological pigment composition, which would also be the main challenges for remote detection of life on the surface of other icy planets and moons. The frontiers of glacier biology on Earth may therefore intersect with the cutting edge search for extraterrestrial life.



While many people think of Arctic and Antarctic ice as lifeless places, there is in fact abundant microbial activity on Earth’s glaciers and ice sheets. But more surprising is the huge impacts of these tiny organisms. By changing the colour of the ice surface, microbes are potentially enhancing the rate at which glaciers and ice sheets are shrinking, but we cannot yet build them into our climate models. The research priority now is mapping these ecosystems from space because this will enable us to estimate their impact on ice melt worldwide and improve our melt forecasts. The same technologies that will enable us to detect life on Earth may eventually be useful tools for searching for icy life elsewhere in the universe. There is also much to be learned about way these microbes function that can educate us about the limits of life in extreme environments. The true sharp edge of glacier biology research involves understanding how these microbes are able to sense, survive and drive environmental change. The study of life on Earth’s ice is deeply interdisciplinary and ultimately it requires us to recognize – as Nordenskjold did – the intricate bridges joining the very big and the very small.



Cameron K, Hodson A J, Osborn M (2012) Carbon and nitrogen biogeochemical cycling potentials of supraglacial cryoconite communities. Polar Biology, 35: 1375-1393

Cook J, Hodson A, Telling J, Anesio A, Irvine-Fynn T, Bellas C (2010) The mass-area relationship within cryoconite holes and its implications for primary production. Annals of Glaciology, 51 (56): 106-110

Cook, J.M., Edwards, A., Irvine-Fynn, T.D.I., Takeuchi, N. 2015. Cryoconite: Dark biological secret of the Cryosphere. Progress in Physical Geography, 40 (1): 66 -111, doi: 10.1177/0309133315616574Cook et al., 2017

Edwards A, Pachebat J A, Swain M, Hegarty M, Hodson A, Irvine-Fynn T D L, Rassner S M, Sattler B (2013) A metagenomic snapshot of taxonomic and functional diversity in an alpine glacier cryoconite ecosystem. Environmental Research Letters, 8 (035003): 11pp

Edwards A, Mur L, Girdwood S, Anesio A, Stibal M, Rassner S, Hell K, Pachebat J, Post B, Bussell J, Cameron S, Griffith G, Hodson A (2014) Coupled cryoconite ecosystem structure-function relationships are revealed by comparing bacterial communities in Alpine and Arctic glaciers. FEMS Microbial Ecology, 89 (2): 222-237

Hand, K.P., Murray, A.E., Garvin, J.B., Brinckerhoff, W.B., Christner, B.C., Edgett, K.S., Ehlmann, B.L., German, C.R., Hayes, A.G., Hoehler, T.M., Horst, S.M., Lunine, J.I., Nealson, H.H., Paranicas, C., Schmidt, B.E., Smith, D.E., Rhoden, A.R., Russell, M.J., Templeton, A.S., Willis, P.A., Yingst, R.A., Phillips, C.B., Cable, M.L., Craft, K.L., Hofmann, A.E., Nordheim, T.A., Pappalardo, R.P., and the Project Engineering Team (2017). NASA, Report of the Europa Lander Science Definition team. Posted Feb 2017.

Stibal M, Sabacka M, Zarsky J (2012a) Biological processes on glacier and ice sheet surfaces. Nature 1554 Geoscience, 5: 771-774

Stibal M, Schostag M, Cameron K A, Hansen L H, Chandler D M, Wadham J L, Jacobsen C S (2014) Different 1558 bulk and active microbial communities in cryoconite from the margin and interior of the Greenland ice 1559 sheet. Environmental Microbiology Reports, DOI: 10.1111/1758-2229.12246

Stibal, M., Schostag, M., Cameron, K. A., Hansen, L. H., Chandler, D. M., Wadham, J. L. and Jacobsen, C. S. (2015), Different bulk and active bacterial communities in cryoconite from the margin and interior of the Greenland ice sheet. Environmental Microbiology Reports, 7: 293–300. doi:10.1111/1758-2229.12246

Takeuchi, N., Dial, R., Kohshima, S., Segawa, T., Uetake, J., 2006. Spatial distribution and abundance of red snow algae on 35 the Harding Icefield, Alaska derived from a satellite image. Geophysical Research Letters, 33, L21502, doi:10.1029/2006GL027819

Uetake, J., Naganuma, T., Hebsgaard, M. B., and Kanda, H. 2010. Communities of algae and cyanobacteria on glaciers in west Greenland. Polar Sci. 4, 71–80. doi: 10.1016/j.polar.2010.03.002

Yallop, M.L., Anesio, A.J., Perkins, R.G., Cook, J., Telling, J., Fagan, D., MacFarlane, J., Stibal, M., Barker, G., Bellas, C., 25 Hodson, A., Tranter, M., Wadham, J., Roberts, N.W. 2012. Photophysiology and albedo-changing potential of the ice-algal community on the surface of the Greenland ice sheet, ISME Journal, 6: 2302 – 2313


Pitching Tents on Ice

In 2017 I slept in various ice-camps in Greenland in spring, summer and autumn. Living on ice requires some specialist techniques different to camping on dry land, and they vary depending on the season. In summer, the main problem is the melting surface. A tent pitched directly on the ice surface will descend into a wet ditch because of the heat generated by a person inside. To counter this, tents are pitched on sheets of ply with reflective insulating sheets underneath. These slow the ablation under the tents and provide a flat surface to sleep on; however, they often work too well and leave the tents wobbling on raised platforms after a few days.

A recently repitched tent sitting next to the platform left behind in its previous position (Greenland Ice Sheet, July 2016)

The most important thing is securing the tent to the ice surface, because it can get very windy on the ice sheet. The ice surface can descend several centimetres per day, meaning short stakes or pins will melt out very fast. For that reason long bamboo or plastic poles are drilled up to 1 metre into the ice at an oblique angle under the tent, providing points to secure the tents to. This is especially important for geodesic dome tents, where tension is required roughly evenly across the poles for the tent to keep its shape. In 2017 the combination of strong winds and very fast surface lowering meant the large mess tent quickly became raised above the surrounding ice and, despite our best repitching efforts, the poles floated freely above the ice. With no ground to push against, the poles became structureless and weak and eventually collapsed.

Drilling holes for 1m bamboo stakes to secure the tent-tags and extra guy-lines in a summer storm (Greenland, 2017)

In winter, a stronger and more permanent solution can be achieved using Abalykov threads. These are loops of tape or rope frozen into the ice itself. There is no surface melting in autumn/winter and the surface does not have a weak weathered layer. The strong, cold surface ice is perfect for drilling obliquely with short ice screws so that two drill-holes meet 10-15cm below the ice surface an create a tunnel from the surface and back. A pipe-cleaner can then be used to drag rope or tape through the hole and tie the tent down. the hole can then be packed with snow or water which will quickly refreeze around the rope and form a super strong tie-point to secure the tent. Using a snow shovel to cover the tent’s snow-skirt with snow helps prevent wind and snow from getting between the flysheet and the inner, keeping it cosy inside and helping to keep the tent a bit better streamlined against the wind.

This Youtube clip posted by Glenmore Lodge (Scotland) explains how to make an Abalykov thread for ice-climbing – it’s the same for securing tents in an ice camp.

The Abalykov threads stood up to extremely strong winds in Greenland in September/October. The poles and fabric seemed more at risk of failure than the threads!