Cryospheric Sciences

Guest author

Did you know? – Proglacial lakes accelerate glacier retreat!

Hooker glacier and its proglacial lake, Aoraki/Mt Cook National Park. [Credit: Jenna L. Sutherland]

In a global context, New Zealand’s small mountain glaciers often get overlooked and yet they are a beautiful part of New Zealand’s landscape. They are the water towers for the South Island and an essential part of its tourism, thanks to a few undeniable heroes (Frans Josef and Fox Glaciers), but sadly, they may not be as prominent in the future. In this post we review the state of modern glaciation in New Zealand, explain why glacier-lake interactions are important and why we need to turn to the past for answers.

Glaciers in New Zealand are losing mass…

New Zealand is home to over 3000 glaciers. However, their mass is quickly declining. New Zealand has one of the oldest and most continuous records of annual ice volume, provided by the End of Summer Snowline Survey, and pioneered by the late Trevor Chinn. Now undertaken by NIWA, aerial surveys on 51 index glaciers have been carried out every year for more than 4 decades (records began in 1977). The surveys document the snowline on the glaciers at the end of every summer, which give us a timeline of glacier-climate interaction. Glacier snowlines, also known as Equilibrium Line Altitudes (ELAs), provide a direct measurement of a glaciers health. They record how much of the previous winter’s snow remains at the end of summer, contributing to long-term glacier ice accumulation. The higher the ELA, the less winter snow remaining, indicating the glacier has shrunk. If the ELA is lower, a larger amount of winter snow remains and the glacier has increased in size. An almost continuous trend from this 40 year archive reveals that glaciers in New Zealand are retreating rapidly – they are getting shorter and losing mass. The significant retreat of Southern Alps glaciers has accelerated over the last decade and recent studies have found that a third of total ice volume has been lost since records began.

…leading to the development of proglacial lakes

The formation of proglacial lakes in mountainous regions, specifically those in contact with the ice margin, is one of the consequences of glacier recession. As a glacier margin retreats, meltwater is impounded in the topographic low between the ice front and the abandoned moraine ridges. The increasing number and size of proglacial lakes is one of the most visually obvious effects of present deglaciation in New Zealand. Most of the existing ice-contact lakes in New Zealand formed when glaciers began to recede from large moraine ridges constructed during the Little Ice Age (LIA), about 150 years ago.

Proglacial lakes currently represent 38 % of the total number of all lakes in New Zealand, and over a third of the country’s perennial ice is contained within lake-calving glaciers. Back in the early 1970s, the Tasman Lake did not exist and the glacier terminated against its outwash sediments. Today, just 40 years later, it now terminates in a large proglacial lake that is more than 8 km long, and over 200 m deep (Figure 1). Since the lake formed, the Tasman Glacier has retreated at an average of 180 m per year and is now in a state of rapid recession.

Figure 1. The Tasman Glacier and its associated proglacial lake. Don’t be fooled by how thin the glacier terminus looks from this perspective, the ice cliff is 50 m tall. The lower part of the glacier is heavily debris-covered but you can see the exposed glacier surface at the head of the valley [credit: Jenna L. Sutherland]

Lake formation is strongly linked to glacier dynamics (Figure 2). The depth of water at the ice margin determines:

  • the distance underneath the glacier that water can travel
  • the rate at which ice calves (or breaks off) from the terminus

Together, these factors increase the speed of ice flow and increase mass loss from the glacier system. The relatively warmer water of the lake compared to the glacier ice also causes thermally-induced melting. An ice-marginal lake can therefore cause glacier margins to fluctuate back and forth, which in turn can cause the speed of the glacier and its mass balance to become partially separated from the climatic signal.

Figure 2. Interactions between the glacier and its proglacial lake. Forces acting upon the glacier are shown in italicised text and with black arrows. The processes between the lake and the glacier are in black text and grey dashed lines [Credit: Jonathan Carrivick, modified from Carrivick and Tweed, 2013]

New Zealand is witnessing unprecedented glacier recession together with lake expansion. It is easy to link one to the other, but the relationship between ice, the development of the lakes, and climate are much more complicated than this. The shift from a land-terminating to a lake-terminating glacier is a defining point in deglaciating environments. This transition represents a threshold and/or tipping point that is critical for the future evolution of the glacier and therefore crucial for us to understand.  Could such glaciers become unstable and catastrophically collapse? Has this happened before? Where and what is this threshold? The current state of knowledge in New Zealand lies in monitoring temporal and spatial evolution of both glaciers and their proglacial lakes. Despite the remarkable record, the short duration of observations in New Zealand (just over 40 years) means that it is difficult to differentiate between natural cycles and occurrences, and dynamic behaviour that is beyond the norm. The answer to such questions lies in turning to the palaeo-record to find out how the Southern Alps ice field has behaved over the last few thousand years or more. It is vital to determine what thresholds control glacier-lake behaviour, and whether these have been crossed in the past. By gaining a deeper understanding of past processes, rates of change, thinning and retreat, as well as previous temperatures and environmental conditions, we will be better placed to understand how the Southern Alps could behave in the future.

Using the past to better understand the future….

The Quaternary record in New Zealand bears witness to the existence of proglacial lakes associated with retreat since the Last Glacial Maximum (LGM; the period between 21,000 and 18,000 years ago). During the LGM, the ice extent and volume was much larger; outlet glaciers advanced beyond the present coastline along the west coast of the South Island (Figure 3). Just like we see in the modern day, the glaciers receded when temperatures began to warm and meltwater ponded, forming large and deep proglacial lakes in contact with the ice margin. Past glacier behaviour in New Zealand has been derived from mapping and dating former ice extents. The maximum extent of ice during previous glaciations is now well constrained, allowing us to determine the speed of glacier recession and thinning. A study has shown that rapid ice recession in the first few millennia saw glacier trunks thin by at least several hundred metres, with implied terminal recession by as much of 40% of the overall glacier length.

Figure 3. The South Island of New Zealand with modern-day glaciers mapped in white and LGM ice extent in light grey. Present day lakes (blue) would have once been in contact with retreating ice margins [Credit: Sutherland et al., 2019]

It has been suggested that the retreat of glaciers in the Southern Alps, immediately after the LGM, was relatively rapid not only because of a warming climate, but also because of the widespread formation of large proglacial lakes accelerating recession. However, despite knowing that large proglacial lakes existed, we have no understanding as to what effect they had on glacier retreat and how much influence these proglacial lakes had on glacier dynamics in combination with climatic warming. The interactions between proglacial lakes and glacier dynamics have not yet been quantified. This is largely a consequence of poor accessibility to modern glacier-lake margins but also because proglacial lakes are currently ignored in ice sheet models (Figure 4). They are treated as an entirely separate component, or, as is more often the case, not at all.

Figure 4. Main components of most ice sheet models (blue), often coupled to other models (green), e.g. ocean and atmosphere models. Note the absence of proglacial lakes as a component of the ice sheet model despite their importance in influencing glacier dynamics [Credit: Jenna. L Sutherland]

…But not without some computer modelling too!

Owing to numerous studies that have dated the recession of ice since 18,000 yrs ago we have a pretty good idea that glacier recession was fast. However, as a concern for the future, what we are more interested in is constraining previous ice volumes and, more specifically, the mechanisms of loss. As well as rates of change, we also need to understand processes of change and how the ice evolved through time. In order to examine and better understand the external (or internal, as the case may be) forcing that drove this rapid recession, we need to resort to relating glacier and climatic changes in numerical ice sheet or glacier simulations.

The physics that govern a glaciers mass balance (the difference between snow gain and snow melt) as well as ice flow are complex. The equations depend on ice thickness, speed, ice and air temperature, elevation, as well as many other factors. Fortunately, these relationships are reasonably well understood and provide the basis of many numerical ice sheet models. We then feed the model with input data, such as topography and past climate, to drive a numerical ice sheet simulation. This enables us to investigate detailed mechanisms driving ice sheet change, such as those between a glacier and its lake and we can become confident in such models when they provide a good fit to the geological record (what we see on the earth’s surface).

The future

Understanding the formation and evolution of proglacial lakes and their outlet glaciers through time can provide insights into the behaviour of glaciers and ice sheets to help us anticipate some of the impacts of present and future deglaciation. Although my research is concerned with just one small valley glacier in a specific region, it is a small step towards a wider understanding of the glacier-lake interaction phenomenon. Of course, every proglacial lake is different, just as every mountain glacier is, but if we can get a handle on what effects a lake had on its glacier in the past, the importance of proglacial lakes might be realised for other regions and more seriously considered when it comes to interpreting glacier response to climatic change.

Further Reading

Edited by Andy Emery

Jenna Sutherland is a final year PhD student in the Department of Geography at the University of Leeds, UK. Her research is focused on the interaction of proglacial lakes and their outlet glaciers during the Last Glacial Maximum in New Zealand, specifically by simulating the presence of proglacial lakes in a numerical ice sheet model and relating these experiments to the sediment-landform record. Her broader interests lie in palaeo-glacial environments. She tweets from @Jennalo13




Cryo-Comm – Degrading Terrains

Cryo-Comm – Degrading Terrains

Beneath dusted peaks of mountain dew
A dense and rigid backcloth skulks,
Worn down and compacted with
Fractured decades of aged powder;
Trodden into rocky outcrops
To lie barrenly against
This frozen, ancient soil.
Subtle shifts of these forgotten rocks
Ripple across subterranean sediments,
Dislodging once-stable foundations
That now cascade like an ocean;
Echoing across the fragile firmament
To loudly denounce their buried past.
Beneath the jutting shadows
Of glaring, metallic stations
We bore artificial holes,
Treading carefully
As we silently caress exposed skin;
Mapping the resistance to our touch
Like goose bumps
Rising to the surface
On a withered, sun-kissed limb.
Charting out these imperfections
Reveals the unevenness
Of our approach,
As broken consequences
Reverberate beneath our feet;
An unheard shot across the bow.

This poem is inspired by recent research, which has found that there has been a clear degradation in mountain permafrost across the central Alps over the past two decades.

Permafrost is permanently frozen ground, consisting of rock or soil that has remained at or below 0ºC for at least two years. In Europe, Arctic permafrost is found only in the northernmost parts of Scandinavia, meaning that mountain permafrost is the dominating permafrost across the continent. This permafrost influences the evolution of mountain landscapes and can severely affect both human infrastructure and safety, with permafrost warming (or thawing) affecting the potential for natural hazards, such as rock falls. Mountain permafrost is also sensitive to climate change and has been affected by a significant warming trend across the European Alps over the last two decades. However, as this permafrost occurs across a large variety of very different locations, any warming trends are far from uniform, and in order to better understand these changes more accurate monitoring is required.

The researchers in this study made use of Electrical Resistivity Tomography (or ERT), a technique which involves inducing a current in the ground, and then measuring the extent to which the flow of this current is resisted (see this previous post). Any resistivity will depend on what the subsurface structure looks like, and it can be used to map geologic variations such as fracture zones, variations in soil structure, and the presence of permafrost. By using long-term ERT monitoring across a network of permanent sites in the central Alps, this research has demonstrated that there has been a noticeable degradation in mountain permafrost over the past 19 years across this region. The researchers have also demonstrated that a degradation is detectable across shorter timescales, a finding which is significant for better understanding the impacts of climate change across the region.

Further reading

The poem and blog post was written by Dr Sam Illingworth, and also features on his website here.

Edited by Jenny Turton

Dr Sam Illingworth is a senior lecturer in science communication at Manchester Metropolitan University, UK. His research focuses on how science can be used to empower society through creative tools and products. To read more of Sam’s poetry and blogs, and to listen to more podcasts, visit He tweets from @samillingworth.

Cryo-Comm – Capturing Ice

Cryo-Comm – Capturing Ice

In this week’s blogpost, author, editor, artist, and outreach expert Marlo Garnsworthy gives some insights into her recent trip to Iceberg Alley, gives you some tips on how to communicate icy science, and shows us her inspirational artwork.

If you’re reading this, ice may be on your mind. Ice is surely on mine.

During my day job as a creative and editor, I dip frequently into Twitter for the latest cryosphere news. Memories of the Antarctic rumble like the thrusters of the research vessels I’ve called home: constant, comforting, and rising to a roar when I need stabilizing. Thoughts of polar science keep me steady and on course.

You may think scientists and creatives are very different. In fact, in the creative world, as in science, success comes with years spent developing wide-ranging technical and communication skills, less-than-stellar pay, so many rejections, and hard-won moments of joy. Both worlds require resiliency, a good attitude, and stamina. Incidentally, these experiences forge the soft skills we need for remote expeditions—we’re tough, don’t sweat the small stuff, and play nicely.


Going South

I first went south in 2017. I was invited by paleoceanographer Rebecca Robinson to sail on SNOWBIRDS Transect, studying diatoms and diatomaceous ooze, from McMurdo Station through the Southern Ocean. Seeing polar ice—from great grinding glaciers through the window of our Hercules LC-130, to the mosaic of melting summer sea ice in the Ross Sea, to massive icebergs drifting by—was transformative. I was in love with polar ice and with my Outreach role. I had to return.

So, I painted a LOT of polar scenes. I networked via social media and APECS workshops. I learned all I could about ice. I teamed up with my brilliant collaborator Kevin Pluck to form


And it all paid off.

I was invited to sail as Onboard Outreach Officer on the JOIDES Resolution, a drilling ship for the International Ocean Drilling Program. Expedition 382—Iceberg Alley took us to the iceberg-strewn Scotia Sea, where we cored millions of years of sediment. It will allow our team, led by Mike Weber and Maureen Raymo, to reconstruct past melting of the Antarctic Ice Sheet.

Of course, melting.

As I’ve gained more intimate knowledge of what is happening to our polar ice, making lasting changes to how I live has become my only moral choice. Not doing all I can to inform others has become unconscionable. I continue my work to connect a wide audience to the beauty and plight of our polar ice, always hoping I will return. Yet equally important to me is helping polar researchers better communicate their work.


Bringing the Poles to the People

We’re lucky that our science involves places of breathtaking beauty and harshness that most can only dream of seeing in person. It’s not difficult to engage people in the adventure. But conveying polar science comes with unique challenges because the subject of our work is so remote.

As an artist, I think, how can I show the subtle shifts in color, contrast, and texture of icy landscapes? The swiftly changing light, the sudden snow squalls, and the roaring of wind and waves—in a still image? The expanse of space and time in something that will fit on page or screen?

As a storyteller, how do I describe the sounds of a ship’s hull as it breaks sea ice? How it feels to live for months on a heaving surface? The thrill as icebergs pass by our vulnerable ship? The delight of breaching humpbacks and circling penguins? The boredom of eating cabbage at every meal? The bonds that form and the emotional costs of being far from home for months?

As a science communicator, I think, what do I want to say? What do I need to convey? Who is my audience? How do I show our scientific objectives in terms they can understand? How do I make grueling hours of lab- and fieldwork exciting and accessible? How can I most effectively use social media? How can I best speak to a crowd? How can I expand our audience?

Above all, how can I show why it all matters?

The public is becoming more aware of polar melting. But there’s a gaping crevasse between hearing something and really internalizing it. There’s a gulf between knowledge and action. Such leaps in consciousness and behavior can happen suddenly like an iceberg calving; more often, they happen as gradually as a glacier flows.

Ice shelf, ocean and sky [Credit: Marlo Garnsworthy].

Telling a Story

Ultimately, it boils down to this: What can we make people feel? I believe effective science emotion turns facts (data) into “truth” (emotion) and that storytelling is our most powerful tool.

All good stories have a beginning, a middle, a climax, and a resolution. When I tell polar stories, I often aim to take people on this journey:

Beginning: Excitement & Wonder

Come on a faraway adventure: Glaciers! Icebergs! Vast icy vistas! Wild storms and massive seas… PENGUINS!

Middle: Interest & Awe

Whoa. That’s a WHOLE lot of ice. Here’s how we study it. Here’s why we study it.

Climax: Anxiety

Here’s how it feels. Yes, it’s melting. It might be far away, but it’s coming to a coastline near you…

Resolution: Hope & Motivation

But it’s not too late. There’s something we can do. Let’s get going! And…


(Always remember to include humor.)

What story will you tell?


Ice & Fire

On Wednesday 25th of September, the IPCC Special Report on the Ocean & Cryosphere in a Changing Climate (SROCC) was released. It’s unlikely to leave us feeling warm and fuzzy. But please let it fire up your passion to creatively share your science.

What skills can you offer? Do you enjoy photography? Making videos? Can you write a funny limerick or poignant haiku? Are you skilled with numbers or writing code? Are you good at building structures? At telling a story? At playing a musical instrument? At organizing things or people? Are you a social media whiz? (If not, it’s time to become one.) Your unique skills, whatever they may be, are waiting to be harnessed for creative sci-comm.

Speak simply. Speak the truth. Above all, speak your truth. Don’t be afraid to let your emotional connection to your work and polar regions show. And amplify others’ Outreach efforts, too. Together, we’re on the vanguard of this battle for awareness and action.

The interesting life found within the Antarctic inspires some of Marlo’s artwork [Credit: Marlo Garnsworthy].

Further links

  • SNOWBIRDS Transect website
  • Pixel Movers and Makers website
  • Iceberg of Antarctica book (free download)
  • Iceberg Alley and Subantarctic Ice and Ocean Dynamics project website
  • Marlo’s website

Edited by Jenny Turton

Marlo Garnsworthy is the author/illustrator of “Iceberg of Antarctica” (available as a free download) and several other books and is seeking her next polar adventure. Find her at and (with Kevin Pluck). Marlo tweets from @MarloWordyBird.

Surviving in cold environments: from microbes under glaciers to queer scientists in the current social context

Surviving in cold environments: from microbes under glaciers to queer scientists in the current social context

On the 5th of July we will celebrate the International Day of LGBTQ+ (lesbian, gay, bisexual, transsexual, queer, and people that do not identify themselves as cis and/or straight) People in Science, Technology, Engineering, and Maths (STEM). Many people will ask: “Why is this day important?” Being a queer scientist in particular, and a queer person in general, can sometimes reminds us of how living organisms feel in extreme environments. In this blog post, I will use the analogy of organisms thriving in harsh environments, to highlight the struggles of LGBTQ+ people in the science community.

I am a geomicrobiologist investigating how microorganisms interact with their surroundings in order to survive and what impact this activity has on the environment in which the microbes live. My PhD focused on the subglacial environment (underneath glaciers), and although it is a well-known fact that microorganisms can survive in extreme conditions, it was not until the late 1990s that the first subglacial bacteria were described (Priscu et al., 1999; Sharp et al., 1999). This discovery led to a shift in the way we regarded the subglacial environment: from a cold, dark, nutrient desert to a microbial oasis, an ironic “hot spot” for life within immense ice masses (Tung et al., 2006), showing a very high abundance of microorganisms (Toubes-Rodrigo et al., 2016).


How can microorganisms survive in a carbon poor and dark environment?

In illuminated environments, plants and photosynthetic bacteria are able to get energy from the sunlight, but this resource is not available under meters and meters of ice. At the bottom of glaciers, where the ice is in contact with the underlying ground, debris can entrain into the ice (Hubbard et al., 2009; Knight, 1997). Microorganisms are able to take advantage of the sediment and produce energy from the minerals to create organic matter in a process called chemolithotrophy. In addition, due to physical interactions between sediment and ice, there is always a thin layer of liquid water (even at sub-freezing temperatures) around the sediment grains, and it is well known that water is one of the most limiting factors for life. The bacteria which get their energy from the minerals and water under the glacier are called chemolithotrophs.

This process continues as glaciers flow across the ground. As glaciers flow, fresh minerals are picked up into the ice, becoming a supply for chemolithotrophs, which in turn enrich the sediment with carbon over time (Telling et al., 2015). The extra carbon then allows for the blooming of microorganisms capable of feeding on it (heterotrophs). Therefore, we have an active ecosystem in such a harsh environment.


How does this link to the LGBTQ+ Community?

This is a very good analogy for the conditions the LGBTQ+ community finds itself in: we usually find that our surroundings are very cold towards us. Just ask a homosexual person what reaction we receive when we are doing something as normal as holding with our partners or ask a trans person about the reaction they receive for their mere existence. Nevertheless, we queer people are capable of not only thriving but also making an impact and changing the mentality around us. As the visibility and representation of queer people continues to grow, people are becoming more educated about queer lives, queer history and the issues we still face. Much like the microbes that enrich the sediment, we enrich society through our diversity. Therefore, events such as the International Day of LGBTQ+ People in STEM are critical to maintaining and furthering the progress we have already made.

We can imagine glaciers as giant conveyor belts, able to transport sediment from the bedrock underneath the ice and release it downstream. The process of transport will not only affect the location of the sediment, but also the chemical makeup of it, due to the activity of microorganisms over years and years. The sediment released from glacier is richer in some of the nutrients, generating fertile soil. Yet again, this a wonderful metaphor: many people have questioned why LGBTQ+ Pride (in STEM) is needed, as LGBTQ+ rights have advanced so much in recent years. However, it is arguably more important now than ever before as, whilst we have made huge progress, we are still the target of hatred. For example, we still find attacks to queer people in cities such as London and Detroit only last week (see articles below) and in many countries around the world, queer existence is either passively ignored or actively threatened.

A number of museums associated with the University of Cambridge Museums are hosting LGBTQ+ Tours, to highlight research by the LGBTQ+ community and to educate the public. Just recently, the Scott Polar Museum ran the ‘Bridging Binaries Tour’ which included information about same-sex behaviour among penguins, and non-normative gender identities in the ancient world [Credit: University of Cambridge Museums].

How can LGBTQ+ initiatives help?

Initiatives such as Pride, LGBTQ+ people in STEM day or the Bridging Binaries Tours increase the visibility of the community: we prepare the soil for queer people to thrive. It helps internally-struggling individuals accept themselves, and highlights that it is ok to be different and that we exist. A discouraging fact for me when I was growing up was the lack of LGBTQ+ role models in science. A lack of role models has a terrible impact on LGBTQ+ people in STEM. Just to give a couple examples taken from PRIDE in STEM: more than 40% of LGBTQ+ people in STEM remain in the closet, having to disguise a fundamental part of themselves. Furthermore, gay, lesbian, and bisexual students are less likely to follow an academic career. When I first started my PhD, I was asked “edit it down” and be less overt about my sexuality, even by friends. Initiatives such as the International Day of LGBTQ+ People in STEM can make our surroundings more welcoming: it gives us a voice, a place. It gives us a space, in which we can express ourselves, and allows us to inspire the new generations of scientists, technologists, engineers, and mathematicians. As with microorganisms, the whole of society needs to stick together, interact and positively feedback all its members. Just as microorganisms thrive and diversify the community under glaciers, LGBTQ+ people should be able to thrive and add balance to the scientific community. This is why we need to nurture, nourish, and celebrate diversity with days such as International Day of LGBTQ+ (lesbian, gay, bisexual, transsexual, queer) People in Science, Technology, Engineering and Maths (STEM), especially in such politically divided and uncertain times. At the last EGU general assembly, a pride@EGU event was held which provided a meeting point for the LGBTQ+ community and allies (non-LGBTQ+ community members who support them). For more information about LGBTQ+ STEM day, please visit

At the last EGU general assembly, the pride@EGU event was well attended. Another event is being planned for the next general assembly in 2020 [Artwork/photo credit: Dr Stephanie Zihms].

Further reading

Edited by Jenny Turton

Dr Mario Toubes-Rodrigo is a post-doctoral research associate at the Open University, UK. Previously, he completed his PhD at the Manchester Metropolitan University. His research focuses on investigating microorganisms which inhabit extreme environments from the lowest layers of glaciers to sulphate-rich lakes, comparing their production of gases to those in the Martian Atmosphere. Mario is an active twitter user and goes by the handle: @micro_mario.

Image of the Week – Looking to the past for answers

Figure 1 – The lateral moraines of the Khumbu Glacier, Nepal (A+B). Taken from the true right of the glacier and the confluence with Changri Nup/Shar. A shows the original photo; B shows the annotation highlighting different moraines. Numbers assigned based on distance from glacier tongue. Dots represent where rock samples were collected from moraine crests. Yellow circle highlights walkers for scale. [Credit: Martin Kirkbride (photo), mapping and sample collection completed by Jo Hornsey]

We’re only just really starting to comprehend the state and fate of Himalayan glaciers due to a scarcity of research along the monumental mountain range. Climbers and scientists have been observing these lofty glaciers since the 1900s. However, is that looking back far enough? Glacier moraines, featuring in this Image of the Week, can reveal change extending back thousands of years.

You may look at Figure 1 and think ‘what is that?! It’s a mess!’ and you would be right to do so. The only glacier ice visible is where ice cliffs break the debris-covered surface of Khumbu Glacier (Figure 2), which begins in the Western Cwm. If you let your eyes adjust to the medley of rocks and many shades of brown, you can start to pick out lines and shapes. Some are highlighted by the sunlight whilst others take a more discerning eye. If your eyesight is very good, you can spot the people on a path in the lower right area (highlighted by the yellow circle), which give a sense of scale to this landscape. These huge mounds of rock and debris (called moraines), though appearing messy and interwoven, are vital pieces of evidence which show how much the glacier is shrinking; extending thousands of years back beyond the satellite record or human observations.

But why the mess?

The young Himalayan fold mountains produce huge amounts of debris due to the extreme weather and ongoing orogeny. The summer monsoon also provides significant amounts of intense precipitation, which erodes slopes and sediment, causing a highly mobile landscape, and a continual cacophonous supply of rocks and sediment to the Khumbu Glacier (Figure 2); creating a surface blanket known as debris cover. This debris alters how the glacier would normally melt and results in the surface of the glacier lowering through time, rather than the terminus retreating as so often seen on ‘clean’ ice glaciers. Though data collection is improving constantly, access to the Khumbu (nearly a week’s trek with several days of altitude acclimatisation) limits the range of monitoring techniques available and reduced oxygen controls your ability to collect data. Whilst there is observational data, such as satellite imagery and observations from explorers/scientists during the 1900s, it is limited in temporal and spatial resolution. This is where my research on glacier moraines comes in.

A longer time frame

I have spent the last year and ¾ (I am a PhD student; I am counting every second!) mapping the landforms which these great bodies of ice leave behind. This mainly consists of mapping lateral moraines (Figures 1 and2) as these represent the height of the glacier surface at the time it built the moraines and can be used to reconstruct a patterns of glacier evolution. These landforms have differing patterns (size, shape, preservation etc) between glacial valleys, sometimes even within the same valley, telling us that there are local and regional differences in glacier behaviour. To uncover when this all happened, I did what every person thinks I do when I tell them my PhD is based in geography; I went to collect rock samples from the glacier moraines (Figures 1 and 3).

Figure 2 – Mapped moraines. The moraines are identified by the different coloured lines (higher numbers represent older moraines). The dots represent the areas where rocks were sampled for dating. The contemporary glacier outlines were taken from the Randolf Glacier Inventory GLIMS data set. The Digital Elevation Model was taken from the High Mountain Asia 8m resolution data set (Shean, 2017). [Credit: Mapping of moraines and sample collection completed by Jo Hornsey].

Rocks can tell the time?

Well, no; they can’t. But using a technique known as Exposure Dating, we can assign an age to a rock surface if we’re sure that surface has been in that position on that landform since it was put there by the glacier. This means, if we choose rocks on the crests of the moraines (similar to the one I am stood on in Figure 3), we can interpret the age we get from that rock as the time that the glacier surface was there building that landform. If we do it for the mapped moraines of the Khumbu Glacier (Figure 2), then we can start to build a timeline of glacier recession. Thanks to studies in the 1980’s  and to a couple done in the early 2000’s (e.g. Richards, et al., 2000; Finkel, et al., 2003), we’re pretty confident that the most glacier proximal landforms were built around 500 years ago during a hemispheric wide cooling event. This event was significant enough to build the towering lateral moraines which are significantly larger than those mounds you can see bordering them in Figure 1. Importantly, this event occurred before the western industrial revolution. Therefore, by looking at moraine building events before this, we can recreate how glaciers were before humanity’s dependence on fossil fuels developed, i.e. a time where glaciers were able to reach a point of stability and build landforms. By including smaller, distal moraines as well as the mammoth slopes of those most proximal to the glacier, we can construct a chronology of the Khumbu Glacier’s behaviour over the Late Holocene (2500 years ago to present in the Himalaya), into the last point of stability, and onto the behaviour we see today.

So, then what?

I’m glad you asked. Once we have a chronology for the glacier’s behaviour, we can start to compare it to the modern-day behaviour. This can be done using direct comparisons between glacier extent and thickness or using glacier models. Models can be useful as they are able to recreate the behaviour between the moraine building phases. I will be applying my chronology to a dynamic glacier model known as iSOSIA, one that was adapted to be able to simulate the development of debris covered glaciers. The chronology will act as parameters within the model (so that it knows the moraines must be built by a certain time), and the model can then recreate the glaciers behaviour whilst it was building these striking landmarks. We can use the model to improve our understanding of how these glaciers have become debris covered, what they would be like if they weren’t, and what might happen to them as climate change continues.

What is this all for?

Having travelled to the Khumbu valley and spent days staggering around on the debris-covered glacier trying in vain to catch my breath, the sense of our impact on the world hit home quite dramatically. Whilst the Khumbu valley is a particularly busy valley, you’re still days away from any form of infrastructure. The moment you travel off the well-worn path, it’s the most incredibly peaceful landscape. Not because it’s silent; the glacier is constantly making noise as it slowly flows down the valley and debris shifts around the surface. It is because it is entirely natural. When there are no helicopters to be heard, in that moment, you could be the only person alive. In the face of an ever-expanding world, I believe it is important to protect and preserve these natural spaces, and those dependent on them.

Humans will not last forever, or even for a long time in the grand scheme of things, but if we’re not careful, our impact might. I don’t think future populations of any species deserve that.

Figure 3 – Looking back up the valley whilst I contemplate a rock. Pumori summit can be seen to the left of the photograph, and Nuptse summit can be seen on the right. Existential questions on a postcard please. [Credit: Martin Kirkbride]

Further Reading

Edited by Scott Watson

Jo Hornsey is a PhD student at the Department of Geography in Sheffield, UK. She is researching the changing extent of Himalayan glaciers over the last 2500 years with specific focus on the Little Ice Age event ~500 years ago; dating the patterns of glacier retreat in the Khumbu Valley; using this information to improve accuracy of the iSOSIA model; and applying IPCC Climate Scenarios to analyse future glacier behaviour in the Khumbu Valley. In her downtime she can be found walking, climbing, running, acting, playing Dungeons and Dragons, and invariably trying to show you pictures of her cats.
Twitter – @joshornsey
Email –

Image of the Week – Unravelling the mystery of the 2017 Weddell Polynya

Figure 1: The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired these images of the Maud Rise or Weddell polynya in the eastern Weddell Sea on September 25, 2017. The first image is natural color and the second is false color where areas of ice are in blue and clouds are in white. [Image credit: NASA Earth Observatory].

The mysterious appearance and disappearance of the Weddell Polynya, a giant hole in the ice, has long puzzled scientists. Recent work reveals that it is tightly tied to energetic storms. Read on to find out more…

The eastern side of the Weddell Sea is a region known for its low concentration of sea ice due to the presence of a seamount, an underwater plateau called the Maud Rise. The seamount influences ocean circulation by bringing warm water closer to the surface, preventing the formation of thick ice. In the early 1970s, when satellites first began snapping photos of Earth, scientists noticed a mysterious hole in Antarctica’s seasonal sea ice floating in this area. This phenomenon is known as a polynya, and for decades its occurrence went unexplained. Then in 2017, during the continent’s coldest winter months, when ice should be at its thickest, a giant 9,500-square-kilometre hole suddenly showed up in the same region (Figure 1). Two months later it had grown 740% larger, before merging with the open ocean at the beginning of the melt season.

The Weddell Polynya is a rather famous hole in the ice (see this previous post). Scientists have been investigating such features in the Southern Ocean for decades, but the true reasons for the appearance and disappearance of the Weddell Polynya were still surrounded by mystery – until now.

Why does the Weddell Polynya form?

Recently, our new study found that these mid-sea polynyas can be triggered by strong cyclonic storms. Using satellite observations and reanalysis data, we found that in some winters, atmospheric circulation moves a significant amount of heat and moisture from mid-latitudes to Antarctica, allowing large cyclones to develop over the sea ice pack. When strong cyclones – some as strong as hurricanes – form and spin over the ice pack, the strong cyclonic winds they can drag the floating sea ice in opposite directions away from the cyclone center, creating the opening.

Sea ice typically drifts in a direction turned 30° on average to the left of the atmospheric flow, with a speed amounting to 1–2% of the surface wind speed. Those rules, when applied to a cyclonic wind situation (i.e., two opposing winds around a center), imply divergence in the motion of sea ice leading to open water area within the cyclone center, as in Fig. 2. We can see how such a situation occurs in real life for the Weddell Polynya when looking at Fig. 3, where near-surface winds exceeding 20 m/s are pushing the ice in opposite directions away from the cyclone center, characterized by weak winds, and the hole in the ice underneath it.

Figure 2: Sketch summarizing the mechanisms by which the cyclone can open the polynya [Credit: Francis et al., 2019].

Why does the Weddell Polynya matter?

Once opened, the polynya works like a window through the sea ice, transferring huge amounts of energy during winter between the ocean and the atmosphere. Because of their large size, mid-sea polynyas are capable of impacting the climate regionally and globally. This includes impact on the regional atmospheric circulation, the global overturning circulation, Antarctic deep and bottom water properties, and oceanic carbon uptake. It is important for us to identify the triggers for their occurrence to improve their representation in models and their effects on climate.

What might happen in the future?

Under future warming-climate conditions, previous studies have predicted an intensification of the activity of polar cyclones and a poleward shift of the extratropical storm track. Others have shown that a poleward shift of the cyclone activity can result in a reduced sea ice extent, a situation similar to that observed in 2016 and 2017. When the sea ice extent is reduced, preferable polynya areas (i.e. areas of thinner ice, for example the Maud Rise) located in the ice pack become closer to the ice edge and hence to the cyclogenesis zone. Given the link between polynya occurrence and cyclones, polynya events may thus become more frequent under a warmer climate.

Figure 3 AMSR2‐derived sea ice concentrations on 16 September 2017 at 1200 UTC (colors) and ERA5 10‐m winds less than 20 m/s in black contours, and greater than 20 m/s in red contours.The solid yellow contour is the 15% ERA‐Interim sea ice contour, the dotted yellow contour is the 50% ERA‐Interim sea ice contour, and the dashed white contour is the 15% ice from satellite data delineating the polynya area. [Credit: Francis et al., 2019].

Further reading

Edited by Lettie Roach

Diana Francis is an atmospheric scientist at New York University Abu Dhabi, UAE. She investigates atmospheric dynamics in polar regions with focus on polar meteorology and links to changes in land and sea ice conditions. To this end, she uses regional models together with available observations and reanalyses. She tweets as @drdianafrancis.
Contact Email:

Climate Change & Cryosphere – Caucasus Glaciers Receding

Climate Change & Cryosphere – Caucasus Glaciers Receding

The Tviberi Glacier valley is located in the Svaneti Region – a historic province of the Georgian Caucasus. Between 1884 and 2011, climate change has led to a dramatic retreat of the ice in this valley. Other glaciers in the Greater Caucasus evolved in a similar way in past decades. We investigated glaciers and their changes both in-situ and with remote sensing techniques in the 53 river basins in the southern and northern slopes of the Greater Caucasus in order to analyze glacier dynamics in combination with climate change over the last decades…

Why are glaciers important for the Caucasus region?

On the one hand, in a high mountain system such as the Greater Caucasus, glaciers are the source of rivers through snow and ice melting. They are therefore an important source of water for agricultural production, for several hydroelectric power stations, for water supply, and for recreational opportunities. Also, the Greater Caucasus glaciers have a positive impact on the economy by being a major tourist attraction. The Svaneti, Racha and Kazbegi regions in Georgia welcome thousands of visitors each year.

On the other hand, glacier hazards are relatively common in this region, leading to major casualties. On the 20th September 2002, for example, Kolka Glacier (North Ossetia) initiated a catastrophic ice-debris flow killing over 100 people, and, on the 17th May 2014, Devdoraki Glacier (Georgia) caused a rock–ice avalanche and glacial mudflow killing nine people (Tielidze and Wheate, 2018).


Tviberi Glacier Degradation over the last century

According to our investigation, the Tviberi was the largest glacier of the southern slope of Georgian Caucasus in the end of the 19th century with a total area of 49.0 km2. The glacier terminated at a height of 2030 m above sea level (a.s.l) in 1887 (based on topographical maps, see Fig.2a). Before the 1960s, the largest ice stream – the Kvitoldi Glacier – separated from the Tviberi, and became an independent glacier (Fig. 2b). The 1960 topographical map shows that, as a consequence, the Tviberi Glacier shrinked to an area of 24.7 km2 and the glacier tongue ended at 2140 m a.s.l. (Fig. 2b). Finally, the Landsat 2014 image shows the degradation of the Tviberi Glacier after 1960, as it decomposed into smaller simple-valley glaciers and even smaller cirque glaciers developed (Fig. 2c) (Tielidze, 2016).

Fig.2: a – Tviberi Glacier, topographical map 1887; b – topographical map 1960, 1: Tviberi Glacier, 2: Kvitlodi Glacier; c – Landsat L8 imagery 2014. [Credit: modified from Fig.2 in Tielidzle, 2016]

Latest Caucasus Glacier Inventory

In our remote-sensing survey of glacier change in the Greater Caucasus based on large-scale topographic maps and satellite imagery (Corona, Landsat and ASTER), we show that the evolution of the Tviberi Glacier reflects the evolution of the majority of glaciers in the region. The main aim of this study was to present an updated and expanded glacier inventory at three time periods (1960, 1986, 2014) covering the entire Greater Caucasus (Russia-Georgia-Azerbaijan).

According to our study, glaciers on the northern slope of the Greater Caucasus lost 0.50% of their area per year between 1960 and 2014, while the southern slope glacier area decreased by 0.61% per year. Glaciers located on Mt. Elbrus lost 0.27% of their combined area per year during the same period. Overall, the total ice area loss between 1960 and 2014 was 0.53% per year, while the number of glaciers reduced from 2349 to 2020 for the entire Greater Caucasus (Fig. 3) (Tielidze and Wheate, 2018).


Fig.3: Greater Caucasus glacier area decrease by slopes, sections and mountain massifs in 1960–1986, 1986–2014 and 1960–2014 [Credit: Fig.4 in Tielidze and Wheate, 2018]

We have observed strong positive linear trends in the mean annual and summer air temperatures at all selected meteorological stations for the period 1960-2014 (Fig. 4). These climate data suggest that the loss of glacier surface area across the Greater Caucasus between the 1960 and 2014 mostly reflects the influence of rising temperatures in both the northern and southern slopes of the Greater Caucasus. The highest temperature increase was recorded in the eastern Greater Caucasus where the glacier recession was highest at the same time. If the decrease in the surface area of glaciers in the eastern Greater Caucasus continues over the 21st century, many will disappear by 2100 (Tielidze and Wheate, 2018).


Fig.4: Mean annual air temperatures at the seven meteorological stations in the years 1960–2014. [Credit: Levan Tielidze]

Want to use these and more data?

This new glacier inventory has been submitted to the Global Land Ice Measurements from Space (GLIMS) database and can be used as a basis data set for future studies.


Further reading

Edited by Clara Burgard

Levan Tielidze is a senior research scientist at Institute of Geography, Tbilisi State University. He is also a PhD student of School of Geography, Environmental and Earth Sciences, and Antarctic Research Centre at Victoria University of Wellington. The field of his research is modern glaciers and glacial-geomorphological studies of the mountainous areas in the Quaternary (Late Pleistocene and Holocene). Contact Email:

Image of the Week – The Lost Meteorites of Antarctica…

Image of the Week – The Lost Meteorites of Antarctica…

 When most people think of Antarctica, meteorites aren’t the first things that come to mind. Perhaps they imagine the huge ice shelves, the desolate interior, or perhaps penguin colonies near one of the scientific bases — but usually not meteorites. So why is our project looking for meteorites in Antarctica, and besides, aren’t they all lost until they are found?

Let’s start with the Antarctic part. Surprisingly, Antarctica is a great place to hunt for meteorites, with two-thirds of all known meteorites found there (see also this previous post). Despite the difficult searching conditions, the dark meteorites show up well on the bright white surface of the ice sheet. Also, due to the cold conditions, the weathering of meteorites is slower than in warmer regions, such as hot deserts. However, Antarctica is vast and most meteorites are small (a few cm in size) so finding them is still difficult. One thing that helps in this case is the presence of mountain ranges and nunataks near the perimeter of the continent. These slow the ice flow and cause stagnation points — blue ice areas (see Fig.1) — where meteorites can collect and accumulate on the surface usually at elevations of 1500m to 2500m or so.

To understand the “lost” part, you need to know that not all meteorites are created equally – some are stony, somewhat like the rocks found in the Earth’s crust, whilst others are more metallic, having a high iron content perhaps close to 90%. The latter tell a meteoriticist (yep, this is a real job definition!) about the cores of planets and the early formation of the solar system. In the rest of the world these rarer and more interesting iron meteorites usually make up about 5.2% of all samples found — but on the ice sheet, they only represent about 0.6%, an order of magnitude less.

This under-representation is a little odd and unexpected. We don’t expect any particular bias due to delivery to Earth, and if you’re out hunting for meteorites on your skidoo and spot a dark rock that’s potentially a meteorite, you’re still going to pick it up: so no bias in collection.

So where are the missing iron meteorites?

About 3 years ago a team from Manchester were looking at this problem and came up with a hypothesis that might explain it: as sunlight enters the blue ice and gets scattered below the surface it gets absorbed by meteorites and heats them up. This happens more on their upper surface, and due to the higher conductivity of iron meteorites in comparison to their stony counterparts, the heat is transferred to the ice below. Given the right conditions during the Austral summer, this process can provide enough energy so that iron meteorites melt the ice underneath them and sink a few centimetres below the surface whilst the stony ones stay on top. Though we put this on a mathematical footing by way of a model and confirmed the mechanism by some laboratory experiments, the only way to be sure that there is a layer of iron meteorites hiding below the surface is to go out and find them.

Fig. 2: Meteorite close-up: partially embedded in the blue ice surface [Credit: Katherine Joy/Lost Meteorites of Antarctica].

The current project

If you’re going to try and find iron meteorites hidden below the ice surface in Antarctica, then you’re going to need a new way of doing things. Ordinarily, searches are carried out by systematically searching an area of blue ice on skidoo and looking for dark rocks that might be potential meteorites (see Fig. 2). Obviously this won’t work for samples below the surface, so we had to come up with a new method that allows a good sized area to be covered (even in a relatively productive area we estimate the density of irons is <1 km-2) and can cope with the conditions up on the Antarctic plateau. Given that the key discriminating characteristic of the subsurface meteorites is their metallic content, it makes sense to use a system based on metal detector technology.

Our system is somewhat different to what you might use for hunting for archaeological coins or have to walk through at the airport, and instead the detector coils are embedded into an array of large polymer panels (the same material the British Antarctic Survey use for transporting fuel drums on). It’s entirely bespoke, including the pulse and detection electronics, data acquisition and analysis, and importantly, it’s designed to be able to deal with the conditions we expect down South.

Fig 3: The prototype detection system being tested at Sky-Blu Field Station during the 2018/19 season. Panels are on the left of the image, control electronics are beneath the photovoltaic panel in the centre, and an indicator box on the skidoo shows when something metallic is detected [Credit: Geoff Evatt/Lost Meteorites of Antarctica].

Even so, given the logistical challenges of remote working in Antarctica (the area we want to search is ~700 km from the nearest base), we thought it prudent to do some tests of the prototype equipment closer to home. To that end, we’ve had two field trips to the UK Arctic Research Station in Ny Ålesund on Svalbard for the initial testing of the detection equipment.

In addition, we need to figure out exactly where to search. We therefore need to confirm an area has surface meteorites before we can hope to find the subsurface layer. That was the point of last Austral summer’s expeditions: while one team kept close to the Sky-Blu base for the first Antarctic test of full detector array, the other team went out to the Recovery Glacier region for a visual search of surface meteorites. Thankfully both were a success, with our meteorite hunting team bringing back a total of 36 surface meteorites.

Fig 4: The meteorite search team’s home for a few weeks. 700 km from Halley and poor weather meant return to civilisation was delayed until the Twin Otter could fly in [Credit: Katherine Joy/Lost Meteorites of Antarctica].

A bit more planning and we’re lined up for next year’s expedition where it all comes together and we find out if the hidden layer is there – or there’s something else at work…

You can find out more about the project and what we’re up to on the project blog:

Further reading

Edited by Clara Burgard

Andy Smedley trained as an atmospheric scientist measuring and modelling how sunlight interacts with the atmosphere. Recently his research interests have expanded to include sunlight’s interaction with, and impacts on, the cryosphere. He is currently working on the Leverhulme Trust funded “Lost Meteorites of Antarctica” project at the University of Manchester where he deals with the logistics of Antarctic field expeditions, mapping and analysis to select the field sites, and trying to better understand how solar radiation interacts with blue ice and light absorbing particles – including meteorites.

Image of the Week – Who let the (sun)dogs out?

Figure 1a: Atmospheric formations on the interior Antarctic plateau near Dome Fuji. Photo credit: B. Van Liefferinge

How peaceful it is to contemplate the sky … This is especially true of polar northern or southern skies where the low temperatures can engender unique light phenomena. We often tend call them all, wrongly, sundogs, but in fact, many more phenomena exist. To list a few, you can observe a parhelic circle, a 22° halo, a pair of sun dogs, a lower tangent arc, a 46° halo, a circumzenithal arc, a parry arc, … This year, I had the chance to observe several of these phenomena during my fieldwork on the Antarctic plateau. I am no cloud specialist or meteorologist, but I would like to give you some explanations to better understand this sky art you might see one day.

Figure 1b: Atmospheric formations on the interior Antarctic plateau near Dome Fuji. Photo credit: B. Van Liefferinge

Everything starts with the ice crystals inside the clouds. Ice crystals can be approximated as hexagonal prisms, and two shapes can be found naturally: plates and columns (Fig.2), mainly dependent on air temperature and humidity. Clouds formed from these ice crystals are relatively thin and therefore sun rays can pass through them easily. In cold regions (polar or not), the ice crystals can also be found at ground level (in that case, they are called diamond dust).

Figure 2: atmospheric halos in the Antarctic plateau, 27 ‎November ‎2018. Plate crystal (left) and column crystal (right), modified from Walter Tape, 1994. Photo credit: B. Van Liefferinge

The observed light patterns in the sky are caused by the refraction of sun rays on the ice crystals. As they hit the crystals, the sun rays are diverted from their trajectory. Depending on the orientation of the crystals in the cloud, and the type of crystal present in the cloud, this will affect the sun ray paths differently. The resulting halos or arcs seen in the sky will result from the combination of all the different ray paths through all the clouds’ crystals together. The sun ray paths through the crystals can become quite complex, as illustrated in Fig. 3.

Figure 3: Example of a complex ray path through a plate crystal which contributes to forming a left parhelic circle (left), example of a complex ray path through a hexagonal crystal which contributed to forming a tricker arc (right), (Walter Tape, 1994). Photo credit: B. Van Liefferinge

As an example, let’s try to understand how the 22° halo forms (see Fig.1 a and b), one of the most common halos observed. The 22° halo is formed in clouds that have randomly oriented column crystals (although this is still under debate). When a sun ray hits an ice crystal, the most common path it will take is to refract through the face of the hexagon it hits (e.g. face 1 on Fig.4) and refract back out of a face opposite (face 3 on Fig.4). The angle between face 1 and face 3 is of 60°. A light ray passing through two faces of an ice crystal inclined at 60° from each other is deflected through angles from 22° up to 50°. The deflection at 22° is the most probable and therefore creates the brightest circle in the sky (the 22° halo!). The other deflections above 22° are less common but occur nonetheless and form the fade disk (Fig. 4). No light can be refracted through smaller angles then 22° (this is a result of the air-to-ice index of refraction). This is why you see a “darker sky” inside the halo. Now, add to this that we have been considering white light in general. But in fact, visible white light is composed of visible red through blue rays, which do not deviate by the same amount (21.54° for red light to 22.37° for blue light). This explains why the 22° halo looks like a rainbow.

Figure 4: Sun ray path through an ice crystal (left), resulting 22° halo (right) [Credit: B. Van Liefferinge].

Now let’s go back to our famous sundog. If you understood the 22° halo, it will be a piece of cloud! Sundogs follow the same rule as the 22° halo: sun rays passing through two ice crystal faces inclined at 60° to each other are deflected through a minimum angle of 22°. The difference here is that for a sundog to form, the ice crystals must all be aligned along the horizontal direction. This is the case when the ice crystals are all plate crystals (Fig.5), which, as a result of their shape, tend to align horizontally in clouds. As sun rays traverse them, they are deflected into two specific spots either side of the sun, instead of along a circle when crystals are randomly oriented (like for the 22° halo).

Figure 5: Sundog formation [Credit: Atmospheric Optics website]

And finally, I’ll let you enjoy a light show, filmed recently over Svalbard on a perfect day for atmospheric formations (video courtesy of Ashley Morris)…


A few more fun facts:

Edited by Marie Cavitte

Brice Van Liefferinge is a trained geographer, glaciologist and modeller. With a background in geography at the Université libre de Bruxelles (ULB, Belgium), he pursued his interest in Earth sciences during his PhD looking at the thermal regime of the Antarctic Ice Sheet and working on the Beyond Epica Oldest Ice project. He is now working on the Oldest Ice Dome Fuji project with Dr. Kenny Matsuoka at the Norwegian Polar Institute (NPI, Tromsø, Norway) for which he just came back from 3 months of fieldwork at Dome Fuji, Antarctica.


Image of the Week – Life in blooming melting snow

Melting snowfields in a forested catchment of glacial lake in Šumava (mid-April), the Czech Republic [Credit: Lenka Procházková]

The new snow melting season has just started in the mountains of Europe and will last, in many alpine places, until the end of June. Weather in the middle of April is changeable. In the last few days sub-zero air temperatures have prevailed in the mountains during the day. In a frame of an international research project, me (Charles University) and Daniel Remias (Applied University Upper Austria), are both packing warm winter clothes as well as all the research equipment necessary for a new field mission: the aims are to find blooming spots of snow algae and to collect it for analyses. Upon our arrival in Šumava, a surprising but wonderful sunny day welcomes the expedition and we regret not taking the sun cream with us. While we are walking on still-compact partly frozen snowfields, our heads feel that they are exposed to hot summer.

Snow blooms – what do they look like?

Red snow colouration at nearly all ice-covered parts of a high-alpine glacial lake (mid-June), High Tatras (Slovakia). Detailed view of red snow after harvest [Credit: Daniel Remias and Lenka Procházková, see study Procházková et al. 2018a]

Snow blooms – see the figure above – can be found in polar and alpine regions worldwide. Availability of liquid water is a key factor for the development of a snow algae population. In our experience, only wet and slowly melting snowfields are suitable.  This colourful phenomenon can appear in different colour shades, as green, yellow, pink, orange or blood-red (Procházková et al., 2018a). Snow blooms are currently a focus of an increasing number of studies because of their significant effects on albedo reduction and subsequent acceleration of snow and ice melting.

Why are they colourful?

A few representatives of microalgae forming blooming snow – a coloured frame of each of these species corresponds with a colour of blooming snowfields [Credit: Lenka Procházková and Daniel Remias]

The macroscopic blooms are caused by microalgae of a cell size ranging from ~5 µm up to ~100 µm. During the melting season, cells live in a water film microhabitat surrounding large snow grains. The main genera that form these blooms are Chloromonas, Sanguina and Chlainomonas, each associated with a specific bloom color (see the figure above).  A massive population development of golden algae can also occur.

When in the season do blooms occur?

Typical seasonal life cycle of a snow alga (Chloromonas nivalis), based on observation over many seasons in European Alps [Figure modified with permission from Sattler et al. 2010]

I would like to reveal a few secrets of snow algae.
The first strategy represents their seasonal life cycle. At the beginning the season in late April, one can hardly see any snow colouration. Snow algae from the previous seasons are lying at the interface between snow and soil in a resistant stage (called cyst). Snow is starting to melt slowly, and the cysts recognize the availability of liquid water and germinate. Flagellates are released and migrate upwards to the sub-surface layers, where they mate. With proceeding melting the cysts are accumulated and exposed at the snow surface. After total snowmelt these resistant stages should survive over summer in soil or at bare rock, where they can be subject to long-distance transport by wind.

The red colour of snow is caused by astaxanthin

A cross-section of a typical snow algal cyst, Chloromonas nivalis-like species, with abundant lipid bodies (“L”) with astaxanthin and plastids (“P”) [transmission electron microscope, credit: Lenka Procházková]

The next strategy of snow algae is an accumulation of the red pigment astaxanthin during their maturation, which has many benefits to life of these microorganisms. For example, astaxanthin is a powerful antioxidant, and its synthesis is not limited by the supply of nitrogen.
Another big advantage of astaxanthin is its protective action against excessive visible and harmful ultraviolet irradiation which are characteristic for snow surfaces in alpine and polar regions. This “sunscreen” effect of astaxanthin – which has maximum absorbance in the visible light region and also a significant capability of UV protection – is supported by the algae’s clever intracellular arrangement (shown in the figure above), namely that sensitive compartments of the algae, like chloroplast or nucleus, are located in the central part, whereas lipid bodies, which accumulate the astaxanthin, are in the periphery.

Our mission

Sequence-related sampling in Lower Tauern, Austria. Checking of a qualitative composition of a sampled spot using light microscope already in field. [Credit: Linda Nedbalová]

Do you wonder why we explore the physiology and biodiversity of snow algae? Because these extremophilic organisms cope with high ultraviolet radiation, repeated freeze-thaw cycles, desiccation, mechanical abrasion, limited nutrients and short season and are well adapted to it! Because of their ability to adapt to these extreme conditions, pigments of snow algae (as the astaxanthin presented above) are even used as biomarkers to detect life on Mars! Moreover, these microalgae are essential primary producers in such an extreme ecosystem, where phototrophic life is restricted to a few specialised organisms. For instance, they provide a basic ecosystem for snow bacteria, fungi and insects. Snow algae communities play an important role in supraglacial and periglacial snow food webs and supply nutrients that will be delivered throughout the glacial ecosystem.


Further reading

                               Edited by Jenny Turton

Lenka Procházková is a PhD Student at the Charles University, Prague, the Czech Republic. She investigates biodiversity and ecophysiology of snow algae. Her favourite algal group is in her focus in a lab as well as in field samplings in the European Alps, High Tatras, Krkonoše, Šumava and Svalbard. Contact Email: