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Image of the Week – Searching for clues of extraterrestrial life on the Antarctic ice sheet

Fig. 1: A meteorite in the Szabo Bluff region of the Transantarctic mountain range, lying in wait for the 2012 ANSMET team to collect it [Credit: Antarctic Search for Meteorites Program / Katherine Joy].

Last week we celebrated Antarctica Day, 50 years after the Antarctic Treaty was signed. This treaty includes an agreement to protect Antarctic ecosystems. But what if, unintentionally, this protection also covered clues of life beyond Earth? In this Image of the Week, we explore how meteorites found in Antarctica are an important piece of the puzzle in the search for extraterrestrial life.


Meteorites in Antarctica

Year after year, teams of scientists from across the globe travel to Antarctica for a variety of scientific endeavours, from glaciologists studying flowing ice to atmospheric scientists examining the composition of the air and biologists studying life on the ice, from penguins to cold-loving microorganisms. Perhaps a less conspicuous group of scientists are the meteorite hunters.

Antarctica is the best place on Earth to find meteorites. Meteorites that fall in this cold, dry desert are spared from the high corrosion rates of warmer, wetter environments, preserving them in relatively pristine condition. They are also much easier to spot mainly due to the contrast between their dark surfaces on the white icy landscape (see our Image of the Week), but also because the combination of Antarctica’s climate, topography and the movement of ice serves to concentrate meteorites, as if lying in wait to be found.

The targeted search for meteorites has taken place annually since the late 1960s, leading to the recovery of over 50,000 specimens from the continent, and counting. The most prolific of these search teams is the US-led Antarctic Search for Meteorites ANSMET), which lay claim to over half of these finds. Comprising only a handful of enthusiasts, this team camps out on the slopes of the Transantarctic Mountains for around 6 weeks hunting for meteorites. The finds include rocks originating from asteroids, the Moon and Mars.

 

Evidence of life in a meteorite?

There has long been a link between meteorites and the potential for life beyond Earth. Perhaps the most famous, or rather infamous, meteorite found in Antarctica is the Alan Hills 84001 meteorite (ALH84001). Found by the 1984 ANSMET team, this meteorite was blasted from the surface of Mars some 17 million years ago as a result of an asteroid or meteorite impact, falling to Earth around 13,000 years ago. This piece of crystallised Martian lava is roughly 4.5 billion years old. The reason for its infamy is the widely publicised claim made a decade after its discovery that it harbours evidence of Martian life [McKay et al 1996]. Specifically, application of high resolution electron microscopy unearthed microstructures comprising magnetite crystals that looked, to the NASA scientist David McKay and his team, like fossilised microbial life, albeit at the nanoscale (see Fig. 2).

Fig.2: A nanoscale magnetite microstructure that was interpreted as fossilised microbial life from Mars [Credit: D McKay (NASA), K. Thomas-Keprta (Lockheed-Martin), R. Zare (Stanford), NASA].

Such a finding of evidence for extraterrestrial life has huge implications for the presence of life beyond Earth, a subject that has captivated humankind since ancient times. This extraordinary claim made headline news across the globe. It even gained acknowledgement by the then US president Bill Clinton. In the words popularised by Carl Sagan, “extraordinary claims require extraordinary evidence”, and this one garnered considerable controversy that endures today. At the time, there was no known process that did not involve life that could result in these types of structures. Subsequent research, triggered by this claim, has since indicated otherwise. The debate rolls on, and it seems we will never really know whether the crystals structures are fossils of Martian life or not, with no conclusive evidence on either side of the argument. Nevertheless, the interest and attention gained through this story kick-started a flurry of hugely successful Mars exploration missions, as well as reinvigorated the search for life beyond Earth.

 

Meteorites as microbial fuel

The ALH840001 is an unusual connection between meteorites and the search for extraterrestrial life. Much subtler, but more wide-reaching, is the potentially important connection between organic-containing meteorites and the existence of life elsewhere. The chondrite class of meteorites originates from the early solar system, specifically from primitive asteroids that formed from the accretion of dust and grains. They are the most common type of meteorite that falls to Earth, and contain a wide array of organic compounds, including nucleotides and amino acids, the so-called building blocks of life. In addition, a number of organic compounds that reside in these meteorites are also common on Earth, and are known to fuel microbial life by serving as a source of energy and nutrients for an array of microorganisms [Nixon et al 2012]. These meteorites have fallen to Earth and Mars for billions of years, since before the emergence and proliferation of life as we understand it. A significant quantity of these meteorites, and the organic matter contained within them, has therefore accumulated on Mars. In fact, owing to the thinner atmosphere of Mars, a larger quantity is expected to have accumulated there than on Earth, and with more of its organic content intact. It is a therefore a distinct possibility that these meteorites may play an important role in the emergence, or even persistence, of life on Mars, if such life has ever existed [Nixon et al 2013].

The search for life on Mars is very much an active pursuit. As we continue this search using robotic spacecraft, such as NASA’s Curiosity rover and the upcoming European Space Agency’s ExoMars rover, we seek to better define whether environments on Mars are habitable for life. But our understanding of habitability on Mars and beyond is defined by our knowledge of the limits of life here on Earth, such as the microbial lifeforms that can make a living on and under the Antarctic ice sheet (see this previous post), but also in terms of the chemical energy able to support life. The search for meteorites on Antarctica has an important role to play here, and long may the hunt continue.

 

References and further reading

Edited by Joe Cook and Clara Burgard


Sophie Nixon is a postdoctoral research fellow in the Geomicrobiology group at the University of Manchester. She completed her PhD in Astrobiology in 2014 at the University of Edinburgh, the subject of which was the feasibility for microbial iron reduction on Mars. Sophie’s research interests since joining the University of Manchester are varied, focussing mainly on the microbiological implications of anthropogenic engineering of the subsurface (e.g. shale gas extraction, nuclear waste disposal), as well as life in extreme environments and the feasibility for life beyond Earth. Contact: sophie.nixon@manchester.ac.uk

Image of the Week – Antarctica Day

Image of the Week – Antarctica Day

Today, 1st December 2017, marks the 58th anniversary of the signing of the Antarctic Treaty in 1959. The Antarctic Treaty was motivated by international collaboration in Antarctica in the International Geophysical Year (IGY), 1957-1958. During the IGY over 50 new bases were established in and around Antarctica by 12 nations- including this one at Halley Bay which was maintained for over a decade before being replaced. These nations signed the Treaty to keep Antarctica as a continent of peace and scientific research. Since 2010, this date has been marked by Antarctica Day, which is used to promote awareness of Antarctica as an international space with benefits for all.


Antarctica as a continent of peace and scientific collaboration

In the year 1957-1958, 67 countries participated in the International Geophysical Year (IGY). This was (a bit confusingly) 18 months of international coordinated observations and data retrieval. The goal was to exploit new tools and techniques to advance science in a huge range of geophysical disciplines. The results, direct and indirect, were widespread. For example it is no coincidence that the first artificial satellite, Sputnik 1, was launched by the USSR in October 1957, after the USA had announced they would launch a satellite as part of IGY activities.

Fig.2: Territorial claims in Antarctica [Credit: Australian Antarctic Data Centre ]

Expeditions in Antarctica were a major activity of the IGY. Seven countries had territorial claims in Antarctica at the time, some of them overlapping (Fig. 2). To make sure that territorial disputes did not hinder scientific progress, it was established that these political goals for Antarctica would be set aside during the IGY, and scientific goals prioritized. As a result, 12 countries operated around Antarctica during the IGY: Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, United Kingdom, United States and USSR. This included those with previous claims as well as those like the USA and USSR who had not previously had activities in Antarctica.

Out of concern for maintaining the scientific legacy of this fantastic year of collaboration, these same 12 countries gathered in 1959 for the “Conference on the Antarctic” in Washington D.C.
The original Treaty had two main components:

  • Antarctica should be used for ‘peaceful means only’. It would not be permitted to establish military bases, carry out military maneuvers, or test weapons.
  • There should be ‘freedom of scientific investigation’. In particular, the Treaty laid out terms of collaboration, such that personnel, information about activities, and the results of scientific observations, should be shared freely.

The Antarctic Treaty covers the area from 60 to 90 degrees south, enclosing the entire Antarctic continent as well as many Antarctic islands and a large area of the Southern Ocean.

 

Future Treaties: Protecting the Environment

The Antarctic Treaty didn’t directly include protections for the environment. However, it did state that future meetings would consider actions related to the Treaty, including those ‘regarding preservation and conservation of living resources in Antarctica’. In the following decades, three major agreements were made to ensure the protection of different aspects of the Antarctic environment.
The first two were the Convention for the Conservation of Antarctic Seals, in 1972, and the Convention for the Conservation of Antarctic Marine Living Resources, in 1982.

The third is the ‘Environmental Protocol’ (full and lengthy name “The Protocol on Environmental Protection to the Antarctic Treaty”). This wide-ranging protocol was signed in 1991 and came into force in 1998, and established the Committee for Environmental Protection. The overarching purpose of the protocol is a commitment “to the comprehensive protection of the Antarctic environment and dependent and associated ecosystems and hereby designate Antarctica as a natural reserve, devoted to peace and science“. It covers all activities in the Antarctic Treaty region, south of 60°S. It lays out reasons for protecting Antarctica – as a home to ecosystems, a unique wilderness, and as a crucial location for scientific research and for understanding the global environment. It outlines types of adverse impact to be avoided; for example, pollution, environmental change, damage to significant locations, and disruption of ecosystems by exploiting them or by introducing foreign species. And, the protocol establishes how such impacts are to be avoided, for example by requiring Environmental Impact Assessments before any activity is carried out.

 

Celebrating the Treaty: Antarctica Day

Inspired by 50 successful years of the Antarctic Treaty, Antarctica Day was launched on the 1st December 2010 and is celebrated on this date each year. Its goals are to celebrate the success of this international coordination treaty and the resulting international peaceful co-operation in Antarctica, raise awareness of the uniqueness of Antarctica, and to encourage conversation and collaboration between students, scientists and officials.

A number of particular activities take place each year. One is an ‘Antarctic flags’ event, organized by the Association of Polar Early Career Researchers (APECS), and currently managed by its UK branch, the UK Polar Network. School children design flags ready for Antarctica Day, which are then proudly displayed by researchers visiting Antarctica over the Antarctic summer (northern hemisphere winter!).

Fig.3: “Los niños de 5to año de la Escuela 163 “Japón” de La Paz- Uruguay”: Antarctica Day 2017 flags designed by school children in Uruguay. [credit: Valentina Cordoba. Provided by Sammie Buzzard.]

If you’re going to Antarctica in the next couple of months and can take a photo of yourself with one of the flags while there, please email education@polarnetwork.org

 

Happy Antarctica day!

 

Further Reading

Edited by Sophie Berger


Caroline Holmes is a postdoctoral researcher at the British Antarctic Survey, UK. She investigates how well sea ice is represented in coupled climate models. The climate models used to project the evolution of the earth system under climate change represent very differing behaviors in terms of the seasonal cycle of sea ice cover at each pole, and trends in the recent past and projected future. Caroline’s work seeks to understand these differing behaviors by examining sea ice processes and atmosphere-ocean-ice linkages. Twitter @CHolmesClimate. Contact Email: calmes@bas.ac.uk

Image of the Week – Does size really matter? A story of ice floes and power laws

Figure 1: Sea ice extent in 2014 during the melting season. The pink lines mark the inner and outer extent of the marginal ice zone. The data comes from the CPOM setup of the CICE sea-ice model run with 9 years spin up from 2005. [Credit: Adam Bateson]

The retreating Arctic sea ice is one of the most well-known facets of Climate Change. Images of polar bears desperately swimming through polar seas searching for somewhere to rest and feed resonate strongly with the public. Beyond these headlines however, the Arctic Ocean is displaying a rapid transition from having mostly permanent ice cover to a more seasonal cover.


The Marginal Ice Zone

As both atmospheric and ocean average temperatures increase over the 21st century, the region of the Arctic considered either marginal or seasonal i.e. regions where sea ice is present for at least some of the year but with periods of either no or incomplete sea ice cover, is projected to increase significantly. Our image of the Week (Fig. 1) shows how the Marginal Ice Zone (defined here as regions with 15 % – 80 % ice coverage) evolves through the melting season. This means that the thermodynamic (i.e. melting, freezing) and dynamic (i.e. mechanical) processes which dominate the marginal ice zone are likely to become more important in influencing how the sea ice evolves in future.

Floe size matters

A key parameter to describe the behaviour of this region is the size of the individual ice floes – sheets of floating sea ice – which form the sea ice cover (see also a previous post on this topic). Floe size impacts melt rate, floe mechanical response, atmosphere-ocean momentum exchange and wave-ice interactions (Fig. 2). The sea ice component of climate models usually assumes all floes have the same, constant size; this assumption removes the ability of sea ice models to represent the complexity of the marginal ice zone. As a result processes which influence floe size such as wave induced break up of floes and lateral melting can’t be represented adequately in current climate models.

Figure 2: Video shows significant wave height in 2014 (darker blue colours indicate bigger waves; note also that a white colour indicates no waves, not necessarily sea ice cover). The purple/pink lines mark the inner and outer extent of the Marginal Ice Zone respectively. The data come from the CPOM setup of the CICE sea-ice model run with 9 years spin up from 2005. [Credit: Adam Bateson]

How can we represent different floe sizes in models?

Given the changing Arctic environment, representing floe size as a variable quantity is likely to be important for future accuracy of sea ice modelling. Currently sea ice models tend to divide the Polar Regions into grid cells, with properties defined as an average across the grid cell. However floe sizes can vary significantly over sub kilometre scales. There are four alternative approaches to representing such a non-uniform distribution of floe sizes within a grid cell:

  1. Define floes individually within the model and allow each floe to evolve independently.
  2. Use a categorical floe size distribution i.e. assign floes to size categories of 1 – 10 m, 10 – 20 m etc. (e.g. Horvat et. al, 2015).
  3. Impose a floe size distribution on each grid cell which evolves over time driven by relevant processes such as lateral melting or floe break-up (e.g. Williams et. al, 2013 a & b).
  4. A single floe size for each grid cell is diagnosed from the fractional ice coverage.

 

Option 1 would be the ideal approach from a Physics perspective. It assumes nothing about what form the floe size distribution may take and allows us to properly assess the impact of different processes for floes of different sizes. This approach is computationally expensive however, which means it will take longer for models to run. Option 4 would the simplest option and wouldn’t have negligible impacts on model run times, however it wouldn’t be possible to include in the model any processes which influence floe size. Option 2 and option 3 represent intermediates between these two extremes. In particular option 3 would be a preferred compromise if floes can be represented as a coherent distribution which evolves over time at the grid length scale.

We should now look at whether observations support the use of such a distribution.

The power law distribution

Figure 3: The cumulative number density for floe size can be represented by a power law. Note that both scales are log scales, and that C in the equation is a constant. The blue and green lines show the distribution for smaller and larger exponents respectively. Note the cumulative number density for a given floe diameter, x, is the fraction of floes size x and larger. [Credit: Adam Bateson]

The floe size distribution is most commonly fitted to a power law (Fig. 3). Power law systems have the property of self-similarity, a term attributed to a system which looks the same over different scales (e.g. the metre or kilometre scale). Power law distributions are relatively easily to investigate mathematically, and can easily be incorporated into a model without significant computational expense.

Do observations support the use of a power law?

Many individual experiments to assess the floe size distribution have shown a good fit to the power law. However, a large range of values for the power law exponent have been reported with observations ranging from 0.9 to 4. Other papers have proposed two power laws over different size ranges, with smaller exponents used for the smaller floe range. Herman et. al (2010) proposed that a distribution with a variable exponent would produce a better fit than a power law. There are further questions we need to consider as well. Over what scale are power laws a valid approximation? What determines the exponent of the power law and can it be assumed that this is constant? Is the power law only valid over a certain range of floe sizes and if so what determines this range?

These questions are not trivial, and the available observations are not sufficient to answer them. However, there is still value in testing different distributions and approaches within models. This can provide information about how sensitive the sea ice cover is to different distributions and which processes in particular are important to accurately model winter ice growth and summer ice loss in the marginal ice zone.

References/Further Reading

Edited by Sophie Berger


Adam Bateson is a PhD student at the University of Reading (United Kingdom), working with Danny Feltham. His project involves investigating the fragmentation and melting of the Arctic seasonal sea-ice cover, specifically improving the representation of relevant processes within sea-ice models. In particular he is looking at lateral melting and wave induced fragmentation of sea-ice as drivers of break up, as well as the role of the ocean mixed layer as either an amplifier or dampener to the impacts of particular processes. Contact: a.w.bateson@pgr.reading.ac.uk or @a_w_bateson on twitter.

Image of the Week – Ice Stupas: a solution for Himalayan water shortage?

Image of the Week – Ice Stupas: a solution for Himalayan water shortage?

As the world searches for practical innovations that can mitigate the impact of climate change, traditional methods of environmental management can offer inspiration. In Hindu Kush and Karakoram region, local people have been growing, or grafting, glaciers for at least 100 years. Legend has it that artificial glaciers were grown in mountain passes as early as the twelfth century to block the advance of Genghis Khan and the Mongols!


 

What exactly are we talking about?

People in the Himalayas need water for the irrigation of their crops. Naturally, they get this water during the melting period of local glaciers. Glacial melt, however, is insufficient to satisfy the demands in early spring (April-June). Artificial ice structures can increase the availability of water for crop irrigation during this period. They are grown during the winter season preventing the water to waste away into the ocean. The Ice Stupa project is bringing these practices back from the realm of folklore for the everyday use of mountain farmers again.

 

How it works

An artificial glacier is built following a simple technique. Water is piped away from high altitude reservoirs (glacial lakes or streams) in winter. Further downstream, the water is allowed to “leave” the pipe. Due to gravity, the pressure that has built up on the way forces the water to leave the pipe as a water fountain. In contact with subzero temperatures, the water fountain freezes, building a huge cone of ice. In its final form, this artificial glacier looks like a traditional buddhist building, hence the name “stupa“. In the following video, you can get a better visual idea of the process!

 

 

An ice stupa is needed for crop irrigation. The water contained in the stupa should therefore also be released during the right time of the year. To this purpose, it is also designed to conserve water in ice form as long into the summer as possible. It can then, as it melts, provide irrigation to the fields until the real glacial melt waters are sufficient in June. Since these ice cones extend vertically upwards towards the sun, they receive less of the sun’s energy per unit of volume of water stored. Hence, they will take much longer to melt compared to an artificial glacier of the same volume formed horizontally on a flat surface.

 

Further reading

Edited by Clara Burgard


Suryanarayanan Balasubramanian is a mathematician who has been managing the Ice Stupa Project for the past three years. He studies the life cycle of Ice Stupas through field measurements and dynamic models. He is currently developing the project in Peru, Switzerland, Nepal and India. Contact Email: gayashiva91@gmail.com

Back to the Front – Larsen C Ice Shelf in the Aftermath of Iceberg A68!

Back to the Front – Larsen C Ice Shelf in the Aftermath of Iceberg A68!

Much of the Antarctic continent is fringed by ice shelves. An ice shelf is the floating extension of a terrestrial ice mass and, as such, is an important ‘middleman’ that regulates the delivery of ice from land into the ocean: for much of Antarctica, ice that passes from land into the sea does so via ice shelves. I’ve been conducting geophysical experiments on ice for over a decade, using mostly seismic and radar methods to determine the physical condition of ice and its wider system, but it’s only in the last couple of years that I’ve been using these methods on ice shelves. The importance of ice shelf processes is becoming more widely recognised in glaciological circles: after hearing one of my seminars last year, a glaciology professor told me that he was revising his previous opinion that ice shelves were largely ‘passengers’ in the grand scheme of things and this recognition is becoming more common. Slowly, we are coming to appreciate that ice shelves have their own specific dynamics and, moreover, that they are the drivers of change on other ice masses.


The MIDAS Project

In 2015, I joined the MIDAS project – led by Swansea and Aberystwyth Universities and funded by the Natural Environment Research Council – dedicated to investigating the effects of a warming climate on the Larsen C ice shelf in West Antarctica (Fig. 1). My role was to to assist with geophysical surveys (Fig. 2) on the ice shelf – but more about that later!

Figure 2: Adam Booth overseeing seismic surveys on the Larsen C ice
shelf in 2015 [Credit: Suzanne Bevan].

Larsen C is located towards the northern tip of the Antarctic Peninsula, and is one of a number of “Larsen neighbours” that fringe its eastern cost. MIDAS turns out to have been an extremely timely study, culminating in 2017 just as Larsen C hit the headlines by calving one of the largest icebergs – termed A68 – ever recorded. On 12th July 2017, 12% of the Larsen C area was sliced away by a sporadically-propagating rift through the eastern edge of the shelf, resulting in an iceberg with 5800 km2 area (two Luxembourgs, one Delaware, one-quarter Wales…). As of 14th October 2017 (Fig. 1), A68 is drifting into the Weddell Sea, with open ocean between it and Larsen C. See our previous post “Ice ice bergy” to find out more about how and why ice berg movement is monitored.

The aftermath of A68

As colossal as A68 (Fig, 1) is, its record-breaking statistics are only (hnnngh…) the tip of the iceberg, and of greater significance is the potential response of what remains of Larsen C. This potential is best appreciated by considering what happened to Larsen B, a northern neighbour of Larsen C. In early 2002, over 3000 km2 of Larsen B Ice Shelf underwent a catastrophic collapse, disintegrating into thousands of smaller icebergs (and immortalised in the music of the band British Sea Power). Rewind seven years further back, to 1995: Larsen B calved an enormous iceberg, exceeding 1700 m2 in area. An ominous extrapolation from this is that large iceberg calving somehow preconditions ice shelves to instability, and several models of Larsen C evolution suggest that it could follow Larsen B’s lead and become more vulnerable to collapse over the coming years.

The enormous mass of the intact ice shelf acts like a dam that blocks the delivery of terrestrial ice into the ocean, and the disappearance of the ice shelf removes so-called ‘backstress’ – essentially ‘breaking the dam’.

Then what? Well, ice shelves are in stress communication with their terrestrial tributaries, therefore processes affecting the shelf can propagate back to the supply glaciers. The enormous mass of the intact ice shelf acts like a dam that blocks the delivery of terrestrial ice into the ocean, and the disappearance of the ice shelf removes so-called ‘backstress’ – essentially ‘breaking the dam’. In the aftermath of Larsen B’s collapse, its tributary glaciers were seen to accelerate, thereby delivering more of their ice into the Weddell Sea. It is this aftermath that we are particularly concerned about, since it’s the accelerated tributaries that promote accelerated sea-level rise. Ice shelf collapse has little immediate impact on sea-level: since it is already floating, the shelf displaces all the water that it ever will. But, in moving more ice from the land to the sea, we risk increased sea levels and, with them, the associated socio-economic consequences.

How can we improve our predictions?

Figure 3: Computational model of the changed stress state, Δτuu, of Larsen C following the calving of A68 (output from BISICLES model, from Stephen Cornford, Swansea University). The stress change is keenly felt at the calving front, but also propagates further upstream [Credit: Stephen Cornford]

A key limitation in our ability to predict the evolution of Larsen C is a lack of observational evidence of how ice shelf stresses evolve in the short-term aftermath of a major calving event. These calving events are rare: we simply haven’t had much opportunity to investigate them, so while our computer predictions are based on valid physics (e.g., Fig. 3) it would be valuable to have actual observations to constrain them. Powerful satellite methods are available for tracking the behaviour of the shelf but these provide only the surface response; Larsen C is around 200 m thick at its calving front so there is plenty of ice that is hidden away from the satellite ‘eye in the sky’, but that is still adapting to the new stress regime. So how can we “see” into the ice?

To address this, we’ve recently been awarded an “Urgency Grant” – Response to the A68 Calving Event (RA68CE) – from NERC to send a fieldcrew to the Larsen C ice shelf, involving researchers from Leeds, Swansea and Aberystwyth, together with the British Geological and British Antarctic Surveys.

Figure 4: Emma Pearce and Dr Jim White preparing seismic equipment – intrepid geophysicists ready to wrap-up warm for field deployment on Larsen C! [Credit: Adam Booth]

The field team – Jim White and Emma Pearce (Fig. 4) – will undertake seismic and radar surveys at two main sites (Fig. 3) to assess the new stress regime around the Larsen C calving front. One of these sites is being reoccupied after seismic surveying in 2008-9, during the Swansea-led SOLIS project, allowing us to make a long-term comparison. These, and two other sites, will also be instrumented with EMLID REACH GPS sensors, to track small-scale ice movements than can’t be captured in the satellite data. The field observations will be supplied to a team of glacial modellers at Swansea University, to allow them to improve future predictions (e.g. Fig. 3), while their remote sensing team continues to monitor the evolving stress state at surface.

It’s truly exciting to be coordinating the first deployment, post A68, on Larsen C. Our data should provide a unique missing piece from the predictive jigsaw of Larsen C’s evolution, ultimately improving our understanding of the causes and effects of large-scale iceberg calving – both for Larsen C and beyond!

 

For ice-hot news from the field, follow Emma Pearce on twitter: @emm_pearce

 

Edited by Emma Smith


Further Reading

  • More information on Larsen C at the project MIDAS website
  • Learn more about ice shelf evolution with the Ice Flows game – eduction by stealth! Also check out the EGU Cryoblog post about it!
  • Borstad et al., 2017; Fracture propagation and stability of ice shelves governed by ice shelf heterogeneity; Geophysical Research Letters, 44, 4186-4194.
  • Wuite et al., 2015; Evolution of surface velocities and ice discharge of Larsen B outlet glaciers from 1995 to 2013. The Cryosphere, 9, 957-969.
  • Cornford et al., 2013; Adaptive mesh, finite volume modelling of marine ice sheets; Journal of Computational Physics, 232, 1, 529-549.

Adam Booth is a lecturer in Exploration Geophysics at the University of Leeds, UK. He is the PI on the NERC-funded project “Ice shelf response to large iceberg calving” (NE/R012334/1). After obtaining his PhD from the University of Leeds in 2008, he held postdoctoral positions at Swansea University and Imperial College London, in which he worked with diverse research applications of near-surface geophysics. He tweets as: @Geophysics_Adam

Image of the Week – Sea-ice dynamics for beginners

Image of the Week – Sea-ice dynamics for beginners

When I ask school children or people who only know about sea ice from remote references in the newspapers: ‘How thick do you think is the Arctic sea ice?’, I often get surprising answers: ’10 meters? No, it must be thicker – 100 meters!’. It seems like sea ice, often depicted as a uniform white cover around the North Pole and as a key element in accelerated warming of the Polar Regions, imposes a majestic image. Unfortunately, sea ice is much more fragile.


Growing in the current

Actually, sea ice is on average just about 2 m thick. It used to be thicker, up to 3 m, but such ice needs several winters to grow and is quite rare in the modern-day Arctic as winters are warmer than they used to be (see this previous post). Currently, more than half of the Arctic sea-ice area melts away completely during summer and grows back during the next winter. Such a thin layer of frozen water floating on the ocean is not strong enough to resist the forces of the wind, which pushes it around in ocean surface currents. In order for the ice to move, it has to deform and breaks into ice floes (read more in this previous post). Some ice floes move apart (divergence) in leads and polynyas (see this previous post), while others are pressed together (convergence) in pressure ridges, where blocks of ice pile up against and on top of each other (see our Image of the Week).

Ice grows from the ocean surface layer by water freezing. This is called thermodynamical growth. Thermodynamical growth produces most of the ice forming in the time from freeze-up in fall until the ice becomes about 1 to 2 m thick in mid-winter. At that point, sea ice approaches equilibrium thickness, i.e. the sea ice is thick enough to insulate the cold atmosphere from the relatively warm ocean. But because sea ice deforms, it can continue growing during the rest of the winter too. Pressure ridges sails can stick several meters out of the icy landscape, while their much larger and bulkier keels are hidden below the surface. Ridges can store large volume of sea ice – about a third (Hansen et al, 2013)! At the same time, new ice can grow in leads where open water is exposed to the atmosphere.

The following video is a collection of movies showing consequences and acts of sea-ice deformation. The first part is taken from R/V Lance – the ice-strengthened research ship of Norwegian Polar Institute, while she is navigating along a lead in late winter. Observe how much space is taken by pressure ridges! The second part of the movie shows a pressure ridge growing. Listen to the sound of deforming ice!

Another positive feedback

In winter, temperatures are so low that all the fractures, leads and pressure ridges freeze back – they heal. In summer, however, these damages are the first to appear again. Dark water with low albedo (read more about the albedo feedback in this post) is exposed and the ice melts faster in such regions. Because the Arctic sea ice became relatively thin over the recent decades, it also became less resistant to the forces of the wind. Such thin ice breaks more easily (e.g. Itkin et al, 2017). This means that, as more of such damaged ice is present in summer, the ice cover melts faster. So, here is an additional positive feedback for the Arctic ice under climate change: thinner ice melts faster also because it has become weaker and therefore breaks up easier.

Further reading

Edited by Clara Burgard


Polona Itkin is a Post-doctoral Researcher at the Norwegian Polar Institute, Tromsø. She investigates the sea ice dynamics of the Arctic Ocean and its connection to the sea ice thickness. In her work she combines the information from in-site observations, remote sensing and numerical modeling. Polona is part of the social media project ‘oceanseaiceNPI’ – a group of scientists that communicates their knowledge through social media channels:

Instagram.com/OceanSeaIceNPI, Twitter.com/OceanSeaIceNPI, Facebook.com/OceanSeaIceNPI, contact Email: polona.itkin@npolar.no

Image of the Week – Karthaus Summer School 2017

Gloriously cloudless day for the fieldtrip to the Ötztal Alps [Credit: C. Reijmer].

Glaciologists often undertake fieldwork in remote and difficult to access locations, which perhaps explains why they happily travel to similar locations to attend meetings and workshops. The Karthaus Summer School, which focuses on Ice Sheets and Glaciers in the Climate System, is no exception. The idyllic village of Karthaus, located in the narrow Schnalstal valley in Südtirol (Italy), has been hosting this 10-day glaciology course nearly every year since 1995. In September, an international crowd of some 30+ PhD students and postdocs, and 11 lecturers assembled in Karthaus for the 2017 edition of this famous course, for an intensive program of lectures, food, some science, more food (with wine!), and lots of socialising.


The lecture theatre with a backdrop of green hills, on the day the cows came down from the hills [Credit: D. Medrzycka].

The morning sessions

A typical morning of the course involved four hours of lectures, which covered a wide range of topics including continuum mechanics, thermodynamics, ice-ocean interactions, ice cores, geophysics, and geodynamics, with a special focus on numerical modelling and its applications for investigating ice-climate interactions. The lectures covered fundamentals processes, their applications and limitations, and current knowledge gaps for a wide range of complex concepts related to ice dynamics. All our lecturers happily answered our (many) additional questions during the coffee and cake breaks, enjoyed in the fresh mountain air outside the lecture theatre.

 
 
 
 
 
 
 

The biggest challenge was not the group work itself, but trying to not get distracted by the sun and the hills surrounding us [Credit: V. Zorzut].

The afternoon sessions

After a three-course lunch, we spent the afternoon sessions applying the theory learned in the morning lectures. The group projects were designed to get us to go into more detail on certain topics, and work on real-world applications for specific research problems. We presented the results of our work at the end of the course during a 15 minute group presentation. For those who could afford a bit of free time after these sessions, the rest of the afternoon could be spent either hiking or trail running in the steep hills overlooking the village (trying to beat I. Hewitt’s time up Kruezspitze), playing football, chilling in the sauna, or catching up on some sleep before dinner.

 

The evenings

Everyone who has ever attended the Karthaus course mentions the food, complementing both the quality and (legendary) quantity of it. Every evening, we were served a memorable five course meal accompanied by generous amounts of local wine. Dessert was followed by musical entertainment, with inspired performances by Frank Pattyn on the piano. On the last evening, Frank was accompanied by Johannes Oerlemans who treated us to two of his original tango arrangements on the guitar, followed by a passionate rendition of Jacques Brel’s Le port d’Amsterdam by our own Kevin Bulthuis (vocals). We wrapped up each day of the course in the local bar, socialising, playing card games, sampling the local beers, and making our way through the many different flavours of schnaps and grappa. Big thanks to the owners, Paul and Stefania Grüner, and staff (with a special shout-out to Hannes) of the Goldene Rose Hotel, and the village of Karthaus, for taking great care of us!

Frank Pattyn (piano) and Johannes Oerlemans (guitar) performing an original tango arrangement [Credit: D. Medrzycka].


 

Out and about

On the penultimate day of the course the group headed to a number of glaciers in the Ötztal Alps. The excursion, which happened to take place on a perfectly cloudless day, gave us the opportunity to observe first hand the changes affecting glaciers in the region, and the impact of these retreating ice masses on the landscape and humans inhabiting it. It also provided a much needed break from the intense week! After walking down the ski slopes of the Hochjochferner, a small valley glacier accessible by cable car from Kurzras, we stopped to enjoy the sun and have lunch at the Schöne Aussicht (Bellavista) hut (2845 m a.s.l.). Those with more energy scrambled up to the ridge running along the Italian/Austrian border (3270 m a.s.l.), through at times knee-deep snow, to take a peak at the Hintereisferner, a valley glacier on the Austrian side of the border. Four of us continued on along the ridge, and by chance visited the laser scanner (LiDAR) system operated by researchers from the University of Innsbruck, used to monitor changes in surface elevation on the glacier.

Standing on the ridge running along the Italian/Austrian border. View onto the Hintereisferner [Credit: D. Medrzycka].


 

Final thoughts

The 10 day course was certainly an intensive (and intense) experience, and I would recommend it to all glaciology students without reservations, whether they are looking for a basic introduction to ice dynamics, or aiming to fill a few knowledge gaps. Whilst some of the topics covered in the course were only remotely related to my own PhD research (and far out of my comfort zone!), the lectures and project work forced me to think in alternate ways. Although I may have finished the course with more questions than I had at the start, I now know where to go look for the answers!

A big part of the experience was without a doubt the social aspect of the course. Between the never ending and excellent food (as a result of which some of us developed “food babies”), and the long evenings at the local bar (resulting in increasing amounts of sleep deprivation), there were plenty of opportunities to talk science, gain new insights into our ongoing research, and discuss ideas for future projects. As with all great Summer Schools, one of the major perks was the opportunity to hang out with fellow students, expand our network of fellow researchers, and establish the groundwork for continued professional collaborations. Huge thanks to the convenor, Johannes Oerlemans, the village of Karthaus, and all the lecturers and fellow students for a memorable 10 days! I am looking forward to working with all of you in the future.

The crowd of the Karthaus summerschool: 2017 edition [Credit: C. Reijmer].

Edited by Morgan Gibson and Clara Burgard


Dorota Medrzycka is a PhD candidate at the University of Ottawa (Canada), working with Luke Copland. Her research focuses on the dynamics of glaciers and ice caps in the Canadian High Arctic, with a focus on ice flow instabilities (including glacier surging). Her project combines field studies and remote sensing techniques to monitor ice motion, and gain insight into the factors controlling the variability in ice dynamics in the Canadian Arctic. Contact: dorota.medrzycka@uottawa.ca.

Image of the Week – Powering up the ground in the search for ice

Electric Resistivity Tomography profile of the north-facing slope of the Rohrbachstein in canton Bern, Switzerland [Credit: University of Fribourg, Switzerland].

In an earlier post, we talked briefly about below-ground ice and the consequences of its disappearing. However, to estimate the consequences of disappearing ground ice, one has to know that there actually is ice in the area of study. How much ice is there – and where is it? As the name suggests, below-ground ice is not so easy to spot with the naked eye. Using geophysical methods, however, it is possible to obtain a good idea of the presence and whereabouts of ground ice, and of frozen ground, in an area of interest.


Looking for ice

Before starting a geophysical survey, which requires instrumentation and time, you might want to take a look at your area of interest and estimate, whether ice presence is even an option. The first indicator is temperature, which has to be in the favor of permafrost presence. Other indicators for presence are surface features such as mounds that could be caused by considerable frost heave, lobes perpendicular to the slope and front angles exceeding the critical angle of repose. They can indicate that ice has had an influence on the geomorphology in the area.

If you suspect ground ice in your area of interest, and you want to confirm or rule out your suspicion as well as investigate the extent of the ice, you might consider doing a geophysical survey. There are a few useful inherent properties of ice that make it possible to distinguish it from rock, air or water. These properties will determine the choice of geophysical methods to use. This week, we will illustrate two methods which, when combined, can be useful tools for determining ground ice presence or absence. The test subject is an area of suspected frozen ground just below 3000 m altitude – the Rohrbachstein in canton Bern, Switzerland.

Electrical resistivity tomography

In an electrical resistivity tomography (ERT) survey, we measure the potential difference (ΔU) of a material, over a given distance, when applied with a certain current strength (I). From the fact that resistance is computed by dividing U by I, the electrical resistivity of the material can be estimated. The resistivity can be seen as the reciprocal of the material’s electrical conductivity and is measured in mΩ. Practically, an array of electrodes are placed in the ground with a certain spacing and a certain length of the profile. The spacing and length of the profile determine the resolution and penetration depth. All electrodes are then connected with a cable to each other and to the instrument, which works as both a voltmeter and a source of current. Then, systematic measurements of potential difference can be conducted throughout the whole profile.

Water has an electrical resistivity of 10-100 mΩ, whereas ground ice has a resistivity of 103 to 106 mΩ. This makes this method practical for distinguishing liquid from frozen water in permafrost areas. The resistivity of rock is between 102 to 105 mΩ, and the resistivity of sediment depends on the mixture of rock, water, ice and air. Air has an extremely high resistivity, which should be easy to point out, but since below-ground material is mostly a mixture of all the mentioned components, things are very often more blurry. What one actually looks for in the measurements is areas of higher, lower and in-between electrical resistivity values. An example of such a case is displayed in our Image of the Week.

Our Image of the Week shows the resistivity profile of a slope at just below 3000 m altitude in the Bernese Alps, Switzerland. For comparison, the same slope is shown in a normal photo in Fig. 2 (not to scale). Blue colours mark high resistivities, red mark low, and green mark somewhere in between. From this profile, we might conclude that the upper layers of the lower slope are moist and underlain by bedrock (red and green, respectively, whereas the upper slope seems to be moist below an area of high resistivity (red below green-blue). Additionally, there is a significant feature of high resistivity in the middle of the slope. This slope could contain ice in those blue areas. However, the high resistivities could also be caused by air volume in this blocky site. To be certain, we can use an additional method.

Fig. 2: Photo of the north-facing slope of the Rohrbachstein in canton Bern, Switzerland. The photo was taken facing east and shows the upper part of the slope analyzed with ERT and seismic refraction, but is not to scale compared with the Image of the Week and Fig.4 [Credit: Laura Helene Rasmussen].

Seismic refraction analysis

To distinguish air from ice, we can do a survey of the subsurface using seismic refraction analysis. Seismic refraction surveys use the fact that the speed (in ms-1) of sound wave propagation is different through different materials. The speed is estimated by placing geophones in a profile line and creating a sound wave by hitting the ground with a sledgehammer in between them (Fig. 3). The geophones detect the sound wave from this hammer blow one by one as it travels through the subsurface, and the time it takes for each geophone to receive the signal is noted. This allows us to calculate the seismic (sound) velocity from the distance and travel time. Different layers in the subsurface with different properties, and thus different seismic velocities, will cause the sound wave arriving at their surface to be refracted with different delay compared to the direct wave (which travels straight from the hammer to each geophone), and that fact can reveal properties of below-ground material.

Fig. 3: Hammer-swinging doing a seismic refraction profile [Credit: Hanne Hendricks].

The advantage of this method for ground ice studies is that ice has a seismic velocity of about 3000 ms-1, whereas sound waves move through air with only 330 ms-1. Thus, a rough profile of that same slope from our Image of the Week and Fig. 2 using seismic refraction geophysics looks like Fig. 4.

In this profile, red colours denote high seismic velocities and blue colours are very low seismic velocities. The high-resistivity feature in the middle of the ERT profile at about 3-4 m depth, which could contain air or ice, would cause red-purple colours (high velocities) if the feature contained ice, and blue colours (low velocities), if it was air volume. As seen from Fig. 4, colours at depths are reddish and certainly not blue, which makes it likely that the ERT feature at 3-4 m depth is actually an ice body. The high-resistivity area in the surface layers of the upper profile, however, corresponds to the blue colours in this seismic refraction profile, and with high resistivity, but low seismic velocity, this area is most likely air volume and not ground ice.

Fig. 4: Seismic refraction profile of the north-facing slope of the Rohrbachstein in canton Bern, Switzerland [Credit: University of Fribourg, Switzerland].

The method depends on the setting

Ground ice does, obviously, come in different forms in different environments, and so the methodological considerations when using geophysical techniques vary in different settings. In this case, we look for ice in a blocky slope. That type of setting presents challenges such as contact problems between sensors and the ground, which can impede the measurements. That issue would not worry a scientist mapping ground ice in a moist Arctic lowland site. The lowland scientist might, however, have to consider resolution issues or salt content in her soil solution when evaluating the results. Perhaps she wants to combine with yet other methods such as drilling permafrost cores for detailed information on ice- and sediment type. As non-destructive methods, covering relatively large spatial areas without having to get a drill rig to the high mountains or a remote Arctic area, however, geophysics can be a good option for ground ice detection.

Further reading

Edited by Clara Burgard and Emma Smith


Laura Helene Rasmussen is a Danish permafrost scientist working at the Center for Permafrost, University of Copenhagen. She has spent many seasons in Greenland, working with the Greenland Ecosystem Monitoring Programme and is interested in Arctic soils as an ecosystem component, their climate sensitivity, functioning and simply understanding what goes on below.

Image of the Week – Bioalbedo: algae darken the Greenland Ice Sheet

Image of the Week – Bioalbedo: algae darken the Greenland Ice Sheet

Most of the energy that drives glacier melting comes directly from sunlight, with the amount of melting critically dependent on the amount of solar energy absorbed compared to that reflected back into the atmosphere. The amount of solar energy that is reflected by a surface without being absorbed is called the albedo. A low albedo surface absorbs more of the energy that hits it compared to a high albedo surface. Our Image of the Week shows patches of dark grey-brown algal blooms on the Greenland Ice Sheet, giving the surface a surprisingly low albedo.


The colour of ice

Clean ice and snow are among the most reflective natural materials on Earth’s surface making them important ‘coolers’ in Earth’s climate system. The term ‘albedo’ describes how effectively a material absorbs or reflects incoming solar energy – it is the ratio of downwelling light arriving at a surface to the amount of upwelling light leaving it. The albedo of fresh, clean snow can be as high as 90%, meaning that out of all the solar energy reaching the surface only 10% is absorbed. However, the albedo of ice and snow can vary widely. This is important because the albedo determines how much of the incoming solar energy is retained within the snow or ice and used to raise the temperature or drive melting. It therefore controls snow and ice energy balance to a large extent.

There are several reasons why the albedo of snow and ice can vary. First, once ice crystals begin to melt they lose their delicate structures that efficiently scatter light and develop rounded granular shapes. Meltwater generated by snow or ice melt fills the gaps between the grains, promoting forward scattering of light deeper into the ice, rather than scattering back towards the surface. This increases the distance travelled through media where absorption can occur, and therefore lowers the albedo as the light is less likely to escape the material after it enters. The more melt, the greater this effect. Second, other materials such as dust or rock debris can enter the snow or ice. These ‘impurities’ generally absorb light more effectively than the ice crystals themselves and therefore reduce the albedo. However, this depends upon their concentration, optical properties and proximity to the surface. Additionally, whether the impurities are inside or outside the ice crystals, where on the planet the material is and the time of day are also important.

Any impurity that darkens a mass of ice or snow increases the amount of solar energy absorbed compared to when the material is impurity-free. This means that impurities promote melting, which is in itself an albedo reducing process. Therefore, the impact of impurities on albedo is non-linear and greater than the direct effect of their absorption alone. There are many different impurities that commonly lower the albedo of ice and snow, including mineral dusts and black carbon (e.g. from fossil fuel combustion). However, there is also a growing literature on another form of impurity that darkens ice and snow on glaciers and ice sheets on both hemispheres: biological growth (also see this previous post). Algae are the primary biological albedo-reducers on ice and snow. Photosynthetic microalgae bloom on the surface where light is abundant, which provides them with energy that they use to turn carbon dioxide and water into sugars. This in turn provides food for other microorganisms. In doing so, they darken the ice surface simply because the algal cells are more effective absorbers than the ice crystals. However, as the algae become exposed to increasing light intensities, they produce pigments that act as sun shields, protecting their cellular machinery from the damaging effects of too much light. This effect enhances the biological darkening and increases the energy absorbed within the snow or ice.

Biological darkening

There are several distinct microbial habitats on glaciers and ice sheets. Snow algae are a feature of melting snowpacks that colour snow surfaces green early in the year and red later because prolonged exposure to sunlight causes them to produce red ‘sunscreen’ pigments (see this previous post). Their influence on snow albedo has yet to be determined, although they have been shown to change the amount of visible light reflected from the surface (Lutz et al., 2014) and in Antarctica they have been shown to influence light absorption at depth within the snowpack (Hodson et al., 2017). Some bacteria have been identified feeding upon the algae, and the algal blooms also provide food for red coloured ice worms. This is probably why, in ‘The History of Animals’, Aristotle wrongly attributed the red discoloration of patches of snow to red worms rather than pigmented algae!

Fig. 2: (a) Albedo for clean snow, bare ice and ice with an algal bloom measured on the Greenland Ice Sheet in July 2017. (b) Microscope image of melted surface ice from the Greenland ice sheet. The red oval shaped particles are ice algae and the angular, clear particles are mineral dust fragments. [Credit: A: J. Cook, B: C. Williamson]

On ice, a different species of algae exists in a thin liquid water film on the upper surface of melting ice crystals. These algae are also photosynthetic but are not bright green or red, but rather grey, brown or purple. They produce a purple pigment that acts as a UV shield that protects their delicate intracellular machinery from excessive light energy. The side effect of this is that the algae become very dark and have an albedo-lowering effect on the ice surface (see our Image of the Week). Ice with algae has a lower albedo than clean ice (Fig 2a) but, up to now, the magnitude of the biological darkening effect has not been quantified because of difficulties isolating algal darkening from that of mineral dusts, soot and the changing optical properties of the ice itself. This also limits our capability to map these algae using remote sensing. Samples of dark coloured ice examined under the microscope clearly show the presence of an algal community darkening the ice (Fig 2b).

In addition to surface-dwelling ice algae, microbial life exists in small pits known as cryoconite holes (see also this previous post). At the bottom of these holes exists a thin layer of granules comprising living microbial cells, dead cells, biogenic molecules, mineral fragments and soot. The organic matter in these granules is very dark, so they warm up when illuminated by the sun and melt into the ice. The relationship between cryoconite and ice surface albedo is complex because, although the cryoconite is dark, the hole geometry hides the granules beneath the ice surface.

Implications for the future of glaciers and ice sheets

The challenge facing scientists now is to quantify the bioalbedo effect by determining the optical properties of individual algal cells and remotely assessing their spatial coverage at the scale of entire glaciers and ice sheets. This will require new methods to be developed for detecting living cells from the air or space. Then, we must understand the factors controlling their growth, so we can predict biological darkening of ice in future climate scenarios. It is possible that algal coverage will increase as glaciers and ice sheets waste away because algae bloom where there is liquid melt water. Because of the darkening effect, an increasingly widespread algal ecosystem in a warming climate will accelerate the demise of its own habitat by enhancing glacier and ice sheet retreat.

Further reading

Edited by Scott Watson and Clara Burgard


Joseph Cook is a Postdoctoral Research Associate on NERC’s Black and Bloom project based at the University of Sheffield, UK where his remit is the measurement and modelling of surface albedo on the Greenland Ice Sheet. His background is in biotic-abiotic interactions on ice. He tweets as @tothepoles and blogs at http://tothepoles.wordpress.com. Contact Email: joe.cook@sheffield.ac.uk

Image of the Week – Drilling into a Himalayan glacier

Image of the Week – Drilling into a Himalayan glacier

How water travels through and beneath the interior of debris-covered glaciers is poorly understood, partly because it can be difficult to access these glaciers at all, never mind explore their interiors. In this Image of the Week, find out how these aspects can be investigated by drilling holes all the way through the ice…


Hydrological features of debris-covered glaciers

Debris-covered glaciers can have a range of hydrological features that do not usually appear on clean-ice valley glaciers, such as surface (supraglacial) ponds. These features are produced as a result of the variable melting that occurs across the glacier surface, depending on the thickness of the debris layer on the surface. Melting is reduced where the debris layer is thick (e.g. near the terminus), which leads to mass loss primarily by thinning, rather than terminus retreat like clean-ice glaciers (read more about this process in this previous blog post). This produces a low-gradient surface covered by hummocks and depressions in which ponds can form, often with steep bare ice faces (ice cliffs) surrounding them. The occurrence of ice cliffs and ponds also affects the surface melt rate, as glacier ice in/on/under these features melts considerably faster (up to 10 and 7 times more, respectively) than that of the debris-covered areas surrounding them (Sakai et al., 2000). Consequently, these hydrological features are an important contributing factor to the general trend of surface lowering of debris-covered glaciers (Bolch et al., 2012).

As a result, most hydrological research on debris-covered glaciers to date has focused on the (more accessible) supraglacial hydrological environment, as well as measuring the proglacial discharge of meltwater from these glaciers, which is a vital water resource for millions of people (Pritchard, 2017). Below the debris-covered surface of these glaciers, next-to-nothing is known about their hydrology; do drainage networks exist within (englacial) or beneath (subglacial) these glaciers, can they exist, and how can they be observed in such challenging environments?

A limited amount of direct research has been carried out in attempt to answer some of these questions, such as speleological techniques to investigate shallow englacial systems on a few glaciers (e.g. Gulley and Benn, 2007; Narama et al., 2017). However, all other inferences of subsurface drainage through debris-covered glaciers have come from hydrogeochemical analyses of water samples taken from the proglacial environment (e.g. Hasnain and Thayyen, 1994) or interpretation of observed glacier dynamics from satellite imagery (e.g. Quincey et al., 2009). While relict englacial features can be observed on the surface of many debris-covered glaciers (Figure 2), studying these systems while they are still active is more difficult.

Fig. 2: A relict englacial feature in the centre of an ice cliff on Khumbu Glacier (looking downglacier), through which the associated supraglacial pond is thought to have drained in the past. Following the drainage event, the pond water-level would have dropped, exposing the ice cliffs around its edge and resulting in the pond water-level being too low to sustain a water flow through the channel. The inset shows the same feature from the far side (looking upglacier): on this side, a vast amount of surface lowering of the ice surface has occurred and the previously englacial channel is now visible from the surface. For scale, the feature is approximately 10 metres in height. [Large image credit: Evan Miles; Inset image credit: Katie Miles]

Hot-water drilling to investigate subsurface hydrology

One way in which potential hydrological systems beneath the surface of debris-covered glaciers can be investigated is through the use of hot-water drilling, as was carried out on Khumbu Glacier, Nepal Himalaya this year by the EverDrill team. A converted car pressure-washer was used to produce a small jet of hot, pressurised water, which was sent through a spool of hose into the drill stem to melt the ice below as it was slowly lowered into the glacier (our Image of the Week). The result (if all went well!) was a borehole 10-15 cm in width, that penetrated the ice all the way to the glacier bed (Figure 3). During the field campaign, we managed to drill 13 boreholes at 3 different drill sites across Khumbu Glacier, ranging in length from 12 to 155 metres.

Once the borehole has been drilled, it can be used to investigate the hydrology of the glacier in a number of ways. If the water level suddenly drops while drilling is in progress, it is possible that the borehole has cut through an englacial conduit, through which the excess drill water has drained. If it drops at the base of a borehole drilled to the bed, it can be assumed that some form of subglacial drainage network exists at the base of the glacier, and the excess water drained through this system. Such features can be examined further through the use of an optical televiewer (360° camera that is lowered slowly through the length of the borehole, taking hundreds of images to give a complete picture of the internal surface of the borehole), or by installing a variety of sensors along the hole’s length to collect various types of data.

Fig. 3: A borehole drilled into Khumbu Glacier during the EverDrill field season in Spring 2017. The borehole was approximately 10 cm in width. A small channel (to the left of the borehole) was formed during the drilling process to drain away the excess water as the borehole was drilled. [Credit: Katie Miles]


During the EverDrill fieldwork in Spring 2017, we televiewed three of the drilled boreholes. These boreholes were then instrumented with sensors to measure the temperature of the ice and, where the boreholes reached the bed, a subglacial probe to measure electrical conductivity, temperature, water pressure and suspended sediment concentration (turbidity). We have left these probes in the boreholes, so that we have measurements both through our field season and additionally through the monsoon summer months. This will allow us to see whether any subsurface hydrological drainage systems develop when there is an additional source of water contributing to the melting of these glaciers. We will return in October to collect this data, and hopefully find out a little more about the englacial and subglacial drainage systems of this debris-covered glacier!

Further reading

Edited by Morgan Gibson, Clara Burgard and Emma Smith


Katie Miles is a PhD student in the Centre for Glaciology, Aberystwyth University, UK, studying the internal structure and subsurface hydrology of high-elevation debris-covered glaciers in the Himalaya by investigating boreholes and measurements that can be made within them. She is also interested in the potential of Sentinel-1 SAR imagery in detecting lakes on the surface of the Greenland Ice Sheet. Katie tweets at @Katie_Miles_851, contact email: kam64@aber.ac.uk