How glacier algae are challenging the way we think about evolution

Wirestock Creators/Shutterstock

People often underestimate tiny beings. But microscopic algal cells not only evolved to thrive in one of the most extreme habitats on Earth – glaciers – but are also shaping them.

With a team of scientists from the UK and Canada, we traced the evolution of purple algae back hundreds of millions of years and our findings challenge a key idea about how evolution works. Though small, these algae are having a dramatic effect on the glaciers they live on.

Glaciers are among the planet’s fastest changing ecosystems. During the summer melt season as liquid water forms on glaciers, blooms of purple algae darken the surface of the ice, accelerating the rate of melt. This fascinating adaptation to glaciers requires microscopic algae to control their growth and photosynthesis. This must be balanced with tolerance of extreme ice melt, temperature and light exposure.

Our study, published in New Phytologist, reveals how and when their adaptations to live in these extreme environments first evolved. We sequenced and analysed genome data of the glacier algae Ancylonema nordenskiöldii. Our results show that the purple colour of glacier algae, which acts like a sunscreen, was generated by new genes involved in pigment production.

This pigment, purpurogallin, protects algal cells from damage of ultraviolet (UV) and visible light. It is also linked with tolerance of low temperatures and desiccation, characteristic features of glacial environments. Our genetic analysis suggests that the evolution of this purple pigment was probably vital for several adaptations in glacier algae.

We also identified new genes that helped increase the algae’s tolerance to UV and visible light, important adaptations for living in a bright, exposed environment. Interestingly these were linked to increased light perception as well as improved mechanisms of repair to sun damage. This work reveals how algae are adapted to live on glaciers in the present day.

Next, we wanted to understand when this adaptation evolved in Earth’s deep history.

The evolution of glacier algae

Earth has experienced many fluctuations of colder and warmer climates. Across thousands and sometimes millions of years, global climates have changed slowly between glacial (cold) to interglacial (warm) periods.

One of the most dramatic cold periods was the Cryogenian, dating back to 720-635 million years ago, when Earth was almost entirely covered in snow and ice. So widespread were these glaciations, they are sometimes referred to by scientists as “Snowball Earth”.

Scientists think that these conditions would have been similar to the glaciers and ice sheets we see on Earth today. So we wondered could this period be the force driving the evolution of glacier algae?

After analysing genetic data and fossilised algae, we estimated that glacier algae evolved around 520-455 million years ago. This suggests that the evolution of glacier algae was not linked to the Snowball Earth environments of the Cryogenian.

As the origin of glacier algae is later than the Cryogenian, a more recent glacial period must have been the driver of glacial adaptations in algae. Scientists think there has continuously been glacial environments on Earth up to 60 million years ago.

We did, however, identify that the common ancestor of glacier algae and land plants evolved around the Cryogenian.

In February 2024, our previous analysis demonstrated that this ancient algae was multicellular. The group containing glacier algae lost the ability to create complex multicellular forms, possibly in response to the extreme environmental pressures of the Cryogenian.

Rather than becoming more complex, we have demonstrated that these algae became simple and persevered to the present day. This is an example of evolution by reducing complexity. It also contradicts the well-established “march of progress” hypothesis, the idea that organisms evolve into increasingly complex versions of their ancestors.

Our work showed that this loss of multicellularity was accompanied by a huge loss of genetic diversity. These lost genes were mainly linked to multicellular development. This is a signature of the evolution of their simple morphology from a more complex ancestor.

Over the last 700 million years, these algae have survived by being tiny, insulated from cold and protected from the Sun. These adaptations prepared them for life on glaciers in the present day.

So specialised is this adaptation, that only a handful of algae have evolved to live on glaciers. This is in contrast to the hundreds of algal species living on snow. Despite this, glacier algae have dramatic effects across vast ice fields when liquid water forms on glacier surfaces. In 2016, on the Greenland ice sheet, algal growth led to an additional 4,400–6,000 million tonnes of runoff.

Understanding these algae helps us appreciate their role in shaping fragile ecosystems.

Our study gives insight into the evolutionary journey of glacier algae from the deep past to the present. As we face a changing climate, understanding these microscopic organisms is key to predicting the future of Earth’s icy environments.The Conversation


This blog is written by Dr Alexander Bowles, Postdoctoral research associate, University of Bristol

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Alexander Bowles
Alexander Bowles

Limiting global warming to 2℃ is not enough – why the world must keep temperature rise below 1℃

Warming of more than 1℃ risks unsafe and harmful outcomes for humanity.
Ink Drop/Shutterstock

The Paris Climate agreement represented a historic step towards a safer future for humanity on Earth when it was adopted in 2015. The agreement strove to keep global heating below 2℃ above pre-industrial levels with the aim of limiting the increase to 1.5℃ if possible. It was signed by 196 parties around the world, representing the overwhelming majority of humanity.

But in the intervening eight years, the Arctic region has experienced record-breaking temperatures, heatwaves have gripped many parts of Asia and Australia has faced unprecedented floods and wildfires. These events remind us of the dangers associated with climate breakdown. Our newly published research argues instead that humanity is only safe at 1℃ of global warming or below.

While one extreme event cannot be solely attributed to global heating, scientific studies have shown that such events are much more likely in a warmer world. Since the Paris agreement, our understanding of the impacts of global heating have also improved.

A fishing boat surrounded by icebergs that have come off a glacier.
Fishing boat dwarfed by icebergs that came off Greenland’s largest glacier, Jakobshavn Isbrae.
Jonathan Bamber, Author provided

Rising sea levels are an inevitable consequence of global warming. This is due to the combination of increased land ice melting and warmer oceans, which cause the volume of ocean water to increase. Recent research shows that in order to eliminate the human-induced component of sea-level rise, we need to return to temperatures last seen in the pre-industrial era (usually taken to be around 1850).

Perhaps more worrying are tipping points in the climate system that are effectively irreversible on human timescales if passed. Two of these tipping points relate to the melting of the Greenland and West Antarctic ice sheets. Together, these sheets contain enough ice to raise the global sea level by more than ten metres.

The temperature threshold for these ice sheets is uncertain, but we know that it lies close to 1.5℃ of global heating above pre-industrial era levels. There’s even evidence that suggests the threshold may already have been passed in one part of west Antarctica.

Critical boundaries

A temperature change of 1.5℃ might sound quite small. But it’s worth noting that the rise of modern civilisation and the agricultural revolution some 12,000 years ago took place during a period of exceptionally stable temperatures.

Our food production, global infrastructure and ecosystem services (the goods and services provided by ecosystems to humans) are all intimately tied to that stable climate. For example, historical evidence shows that a period called the little ice age (1400-1850), when glaciers grew extensively in the northern hemisphere and frost fairs were held annually on the River Thames, was caused by a much smaller temperature change of only about 0.3℃.

A sign marking the retreat of a glacier since 1908.
Jasper National Park, Canada. Glaciers used to grow extensively in the Northern Hemisphere.
Matty Symons/Shutterstock

A recent review of the current research in this area introduces a concept called “Earth system boundaries”, which defines various thresholds beyond which life on our planet would suffer substantial harm. To avoid passing multiple critical boundaries, the authors stress the need to limit temperature rise to 1℃ or less.

In our new research, we also argue that warming of more than 1℃ risks unsafe and harmful outcomes. This potentially includes sea level rise of multiple metres, more intense hurricanes and more frequent weather extremes.

More affordable renewable energy

Although we are already at 1.2℃ above pre-industrial temperatures, reducing global temperatures is not an impossible task. Our research presents a roadmap based on current technologies that can help us work towards achieving the 1℃ warming goal. We do not need to pull a technological “rabbit out of the hat”, but instead we need to invest and implement existing approaches, such as renewable energy, at scale.

Renewable energy sources have become increasingly affordable over time. Between 2010 and 2021, the cost of producing electricity from solar energy reduced by 88%, while wind power saw a reduction of 67% over the same period. The cost of power storage in batteries (for when the availability of wind and sunlight is low) has also decreased, by 70% between 2014 and 2020.

An aerial photograph of a photovoltaic power plant on a lush hillside.
A photovoltaic power plant in Yunnan, China.
Captain Wang/Shutterstock

The cost disparity between renewable energy and alternative sources like nuclear and fossil fuels is now huge – there is a three to four-fold difference.

In addition to being affordable, renewable energy sources are abundantly available and could swiftly meet society’s energy demands. Massive capacity expansions are also currently underway across the globe, which will only further bolster the renewable energy sector. Global solar energy manufacturing capacity, for example, is expected to double in 2023 and 2024.

Removing carbon dioxide from the atmosphere

Low-cost renewable energy will enable our energy systems to transition away from fossil fuels. But it also provides the means of directly removing CO₂ from the atmosphere at a large scale.

CO₂ removal is crucial for keeping warming to 1℃ or less, even though it requires a significant amount of energy. According to research, achieving a safe climate would require dedicating between 5% and 10% of total power generation demand to effective CO₂ removal. This represents a realistic and attainable policy option.

Various measures are used to remove CO₂ from the atmosphere. These include nature-based solutions like reforestation, as well as direct air carbon capture and storage. Trees absorb CO₂ from the atmosphere through photosynthesis and then lock it up for centuries.

A group of people planting a mangrove forest next to the sea.
A mangrove forest being planted in Klong Khone Samut Songkhram Province, Thailand.
vinai chunkhajorn/Shutterstock

Direct air capture technology was originally developed in the 1960s for air purification on submarines and spacecrafts. But it has since been further adapted for use on land. When combined with underground storage methods, such as the process of converting CO₂ into stone, this technology provides a safe and permanent method of removing CO₂ from the atmosphere.

Our paper demonstrates that the tools and technology exist to achieve a safer, healthier and more prosperous future – and that it’s economically viable to do so. What appears to be lacking is the societal will and, as a consequence, the political conviction and commitment to achieve it.



This blog is written Cabot Institute for the Environment member Jonathan Bamber, Professor of Glaciology and Earth Observation, University of Bristol and Christian Breyer, Professor of Solar Economy, Lappeenranta University of TechnologyThis article is republished from The Conversation under a Creative Commons license. Read the original article.

Jonathan Bamber
Jonathan Bamber

Life in the deep freeze – the revolution that changed our view of glaciers forever

I’ve been fascinated by glaciers since I was 14, when geography textbooks taught me about strange rivers of ice that crept down yawning valleys like giant serpents stalking their next meal. That kernel of wonder has carried me through a career of more than 25 years. I’ve travelled to the world’s peaks and its poles to see over 20 glaciers. Yet, when I first started out as a researcher in the early 1990s, we were convinced glaciers were lifeless deserts.

Then in 1999, Professor Martin Sharp and colleagues discovered bacteria living beneath the Haut Glacier d’Arolla in Switzerland. It seemed that glaciers, like the soil or our stomachs, had their own community of microbes, their own microbiome. Since then, we’ve found microorganisms just about everywhere within glaciers, transforming what we thought were sterile wastelands into vibrant ecosystems.

So what’s all that glacier life doing? These life forms may be invisible to the naked eye, but they can control how fast glaciers melt – and may even influence the global climate.

The glacier microbiome

Just like people, glacier microbes modify their homes. When I first saw the melting fringes of Greenland’s vast ice sheet, it looked as if a dust storm had scattered a vast blanket of dirt on the ice. Our team later discovered the dirt included extensive mats of glacier algae. These microscopic plant-like organisms contain pigments to help them harvest the Sun’s rays and protect them from harsh UV radiation. By coating the melting ice surface, they darken it, ensuring the ice absorbs more sunlight which causes more of it to melt. In western Greenland, more than 10% of the summer ice melt is caused by algae.

Bright blue glacier ice on rocky terrain.
The margin of Engabreen glacier, Norway.
Grzegorz Lis, Author provided

Again, just like us, microbes extract things from their environment to survive. The murky depths of glaciers are among the most challenging habitats for life on Earth. Microbes called chemolithotrophs – from the Greek meaning “eaters of rock” – survive here without light and get their energy from breaking down rock, releasing vital nutrients like iron, phosphorous and silicon to the meltwater.

Rivers and icebergs carry these nutrients to the ocean where they sustain the plant-like phytoplankton – the base of marine food webs which ultimately feed entire ecosystems, from microscopic animals, to fish and even whales. Models and satellite observations show a lot of the photosynthesis in the iron-starved Southern Ocean could be sustained by rusty icebergs and meltwaters, which contain iron unlocked by glacier microbes. Recent evidence suggests something similar occurs off west and east Greenland too.

A microscope image depicting chains of brown rectangular cells.
Glacier algae from the Greenland ice sheet.
Chris Williamson, Author provided

But glacier bugs also produce waste, the most worrying of which is the greenhouse gas methane. When ice sheets grow, they bury old soils and sediments, all sources of carbon and the building blocks for earthly life. We think there could be thousands of billions of tonnes of carbon buried beneath ice sheets – potentially more than Arctic permafrost. But who can use it in the oxygen-starved belly of an ice sheet? One type of microbe that flourishes here is the methanogen (meaning “methane maker”), which also thrives in landfill sites and rice paddies.

A waterfall at the edge of a glacier.
Leverett Glacier’s wild river, Greenland.
Jemma Wadham, Author provided

Some methane produced by methanogens escapes in meltwaters flowing from the ice sheet edges. The clever thing about microbial communities, though, is that one microbe’s waste is another’s food. We humans could learn a lot from them about recycling. Some methane beneath glaciers is consumed by bacteria called methanotrophs (methane eaters) which generate energy by converting it to carbon dioxide. They have been detected in Greenlandic glaciers, but most notably in Lake Whillans beneath the West Antarctic Ice Sheet. Here, bacteria have years to chomp on the gas, and almost all of the methane produced in the lake is eaten – a good thing for the climate, since carbon dioxide is 80 times less potent as a greenhouse gas when measured over two decades.

We’re not sure this happens everywhere though. Fast-flowing rivers emerging from the Greenland Ice Sheet are super-saturated with microbial methane because there just isn’t enough time for the methanotrophs to get to work. Will melting glaciers release stored methane faster than these bacteria can convert it?

Within the thick interior of ice sheets, scientists worry that there may be vast reserves of methane. The cold and high pressure here mean that it may be trapped in its solid form, methane hydrate (or clathrate), which is stable unless the ice retreats and thins. It happened before and it could happen again.

Waking the sleeping giant

Despite the climate crisis, when I spend time around glaciers I’m not surprised by their continuing vitality. As I amble up to the gently sloping snout of a glacier – traversing its rubbly lunar-like fore-fields – I often feel like I’m approaching the hulk of an enormous creature. Sleeping or seemingly dormant, the evidence of its last meal is clear from the mass of tawny-coloured rocks, pebbles and boulders strewn around its edges – a tantalising record of where it once rested when the climate was cooler.

As I get closer, I catch the sound of the glacier’s roaring chocolate meltwaters as they explode through an ice cave, punctuated by a cascade of bangs and booms as moving ice collapses into hollow melt channels below. The winds off the ice play ominously in my ears, like the whisper of the beast, a warning: “You’re on my land now.”

The author inside a giant icy chasm within a glacier.
Exploring a frozen melt channel of the Finsterwalderbeeen glacier in Svalbard.
Jon Ove Hagen, Author provided

This sense of aliveness with glaciers changes everything. Resident microbes connect these hulking frozen masses with the Earth’s carbon cycle, ecosystems and climate. How will these connections change if we take away the frigid homes of our tiny glacier dwellers? These creatures may be microscopic, but the effects of their industry span entire continents and oceans.

After a period of uncertainty in my own life, which involved the removal of a satsuma-sized growth in my brain, I felt compelled to tell the story of glaciers to a wider audience. My book, Ice Rivers, is the result. I hope the memoir raises awareness of the dramatic changes that threaten glaciers – unless we act now.The Conversation


This blog is written by Cabot Institute for the Environment Director Jemma Wadham, Professor of Glaciology, University of Bristol.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Professor Jemma Wadham



World Water Day 2021: What does water mean to the Cabot community?


It’s World Water Day (22 March) and we have joined the global public campaign on the theme for 2021 of valuing water. The campaign is designed to generate a worldwide conversation about how different people in different contexts value water for all its uses.
So we asked researchers, students and staff at the Cabot Institute for the Environment, what does water mean to you? Whether it is something learnt through research, personal experiences or simply what you think when you think of water, we asked our community for stories, thoughts, and feelings about water!
All responses including ours and many others across the world will be compiled by UN-Water to create a comprehensive understanding of how water is valued and to help safeguard this resource in a way that will benefit us all.
Cabot Institute for the Environment researchers and students are doing lots of wonderful and important work to deliver the evidence base and solutions to protect water (find out more). Here is what some of them shared with us for World Water Day #Water2me.

What does water mean to you?

“Water is the most special substance on Earth. Everyone has a relationship with it. It is ubiquitous yet still enigmatic. As a hydrologist I have been working for years to better understand where it goes after it rains. As a person who grew up in semi-arid Cyprus, I know that water scarcity can shape a culture as much as it shapes the landscape. As a person who has been living in the UK, I know that too much water can also shape a culture. Too little or too much – water is both a life giver and a life taker. It is everywhere, nowhere, hidden, precious, ever changing, elusive, wondrous, yet taken for granted.   Dr Katerina Michaelides, Co-lead of Cabot Institute for the Environment water theme 


“Liquid water can take any shape of its recipient. As water vapor, it becomes invisible and travels into the air… but it is still there. As ice and it can sometimes provide a hard surface. Water reminds me of adaptation and opportunities. We face a global challenge in ensuring water to all living beings on Earth, but the nature of water tells me that we must adapt to any changes coming in future years and turn challenges into opportunities to develop more sustainable and earth-friendly measures to tackle our societal needs.” – Dr Rafael Rosolem, Co-lead of Cabot Institute for the Environment water theme 



“Water is the essence of life and its tiny moving molecules connect almost everything on Earth – bodies of water in rivers, glaciers, oceans, atmospheres are connected to our bodies as humans. What happens in one body trickles down and impacts others, so we have to be careful with how we manage this vast cycle of water, and of life.” – Professor Jemma Wadham, Director of Cabot Institute for the Environment 


“When you grow up in a country, where 2/3 is a desert with 1 hour of water supply per 48 hours (mainly at 2am!), water is more precious than oil and sometimes gold.” – Dr Hind Saidani-Scott, Cabot Institute for the Environment researcher 
“Simply put, water means health, safety, and life 💧 Without clean water, access to this becomes limited, whereas with it – we can thrive 🌍” – Olivia Reddy, University of Bristol PhD candidate and member of Cabot Institute for the Environment ‘Cabot Communicators’ group.


As a kid to me water meant fun, it sparked feelings of joy and excitement for swimming in the ocean and having a good time. While water remained a magical thing to me, as I grew older, I began to consider its role as a global resource, its precarity, need for protection and how lucky I was to have access to it. Now as I undertake my research at Cabot, I am learning more about the spirituality and sacrality of water amongst indigenous cultures, not only as a “resource” but at as point for worship, ceremony, and community and something to learn from. Today I understand water as part of us as well as our world” – Lois Barton, post-graduate researcher, Global Environmental Challenges, Cabot Institute for the Environment       


“The first thing I would have said when asked to think about water two years ago is a refreshing glassful from the tap. But watching the film Cowspiracy and following this up with my own research into animal agriculture has made me look at water differently. Now, I think of water in terms of cows. 2,500 gallons of water are needed to produce one pound of beef. Animal agriculture is responsible for up to 33% of freshwater usage globally! For me, a new understanding of water and water-use was a key factor in prompting the decision to change to a plant-based diet and advocate that others do the same for the good of the planet and the people who do not have water on tap like I do every day. – Lucy Morris, post-graduate researcher, Global Environmental Challenges, Cabot Institute for the Environment

Hidden Water: Valuing water we cannot see 

Cabot Institute for the Environment is also hosting a public event for World Water Day (17:15 GMT, 22 March 2021) which is bringing together two leading researchers to discuss the value of ‘hidden water’ resources: groundwater and glaciers. 
Dr Debra Perrone, University of California, will discuss her research which revealed millions of groundwater wells and strategies to protect them. Professor Jemma Wadham, Cabot Institute for the Environment, will discuss the impacts of glacier retreat in the Peruvian Andes and solutions to adapt to these changes. Chaired by Cabot Institute for the Environment water experts, Dr Katerina Michaelides and Dr Rafael Rosolem. More information here

Join the discussion

What does water mean to you? Tag @cabotinstitute and #WorldWater #Water2me on Twitter to let us know.



This blog is written by Adele Hulin, Cabot Institute Coordinator at the University of Bristol, and Lois Barton, Cabot Institute for the Environment MScR student and temporary communications assistant at the Institute.
Adele Hulin
Adele Hulin

Just the tip of the iceberg: Climate research at the Bristol Glaciology Centre

As part of Green Great Britain Week, supported by BEIS, we are posting a series of blogs throughout the week highlighting what work is going on at the University of Bristol’s Cabot Institute for the Environment to help provide up to date climate science, technology and solutions for government and industry.  We will also be highlighting some of the big sustainability actions happening across the University and local community in order to do our part to mitigate the negative effects of global warming. Today our blog will look at ‘Explaining the latest science on climate change’.

Last week the Intergovernmental Panel on Climate Change (IPCC) released its special report on the impact of global warming of 1.5˚C. Professor Tony Payne – Head of the University of Bristol’s School of Geographical Sciences and Bristol Glaciology Centre (BGC) member – is one of the lead authors on the report, which highlights the increased threats of a 2˚C versus 1.5˚C warmer world. The report also lays out the mitigation pathways that must be taken if we are to meet the challenge of keeping global warming to 1.5˚C above pre-industrial levels.

The core of the report is a synthesis of over 6000 scientific papers detailing our current understanding of the climate system, and here at the BGC our research is focused on the role of the cryosphere in that system. The cryosphere, which refers to all the snow, ice and permafrost on the planet, is changing rapidly under global warming, and understanding how it will continue to evolve is critical for predicting our future climate. This is primarily due to the positive feedback loops in which it is involved, whereby a small change in conditions sets off a sequence of processes that reinforce and amplify the initial change. Despite the name, in the context of our current climate these positive feedback loops are almost always bad news and are responsible for some of the “tipping points” that could lead to runaway changes in the climate system.

I hope this post will give you a quick tour of just some of the research being carried out by scientists at the BGC, studying the way in which mountain glaciers, sea ice and the two great ice sheets of Antarctica and Greenland are responding to and influencing our changing climate.

Ice sheets

My own research examines ice flow at the margins of Antarctica. The Antarctic ice sheet is fringed by floating ice shelves, fed by large glaciers and ice streams that flow from the heart of the ice sheet towards the coast (see Figure 1). These ice shelves can provide forces that resist the glaciers that flow into them, reducing their speed and the amount of ice that enters the ocean. Crucially, once ice flows off the land and begins to float it causes the sea level to rise. My work is in modelling the interaction between ice shelves and the rest of the ice sheet to better quantify the role that ice shelves have in restraining ice loss from the continent. This will help to reduce the uncertainty in our predictions of future sea level rise, as the thinning and collapse of Antarctic ice shelves that we have seen in recent decades looks set to continue.

Figure 1: Schematic of the Antarctic ice sheet grounding line. Image credit: Bethan Davies,

To model ice flow in Antarctica with any success it is crucial to know the exact location of the point at which the ice sheet begins to float, called the ‘grounding line’. Research on this within the BGC is being done by Dr Geoffrey Dawson and Professor Jonathan Bamber, using data from the European Space Agency’s CryoSat-2 satellite. Their method determines the location of the grounding line by measuring the rise and fall of the floating ice shelves under the influence of ocean tides. Recently published work from this project has improved our knowledge of the grounding line location near the Echelmeyer ice stream in West Antarctica and this method is currently being rolled out across the rest of the ice sheet [1].

In the Northern Hemisphere, the Black and Bloom project led by Professor Martyn Tranter is studying ice algae on the second largest ice mass on Earth, the Greenland Ice Sheet (GrIS). The large, dark regions that appear on the GrIS in the summer are, in part, down to blooms of algae growing in the presence of meltwater on the ice sheet (see Figure 2). This bloom is darker than the surrounding ice surface and so reduces the albedo (a measure, between 0 and 1, of a surface’s reflectivity). A reduced ice sheet albedo means more of the sun’s energy is absorbed and the surface becomes warmer, which produces more meltwater, and more algae, leading to more energy absorption in a classic example of a positive feedback loop. The aim of the project, a partnership between biologists and glaciologists within the BGC, is to take measurements of algal growth and to incorporate their effect on albedo into climate models. A recent paper from the group, led by Dr Chris Williamson, revealed the abundance and species of microbial life that are growing on the GrIS [2], and this summer the team returned to the field to extend their work to more northerly regions of the ice sheet.

Figure 2: Bags of surface ice collected on the Greenland Ice Sheet showing the change in albedo with (from left to right) low, medium and high amounts of algae present.

Sea ice

Moving from land-based ice and into the ocean, Arctic sea ice is also being studied within the BGC. Regions of the Arctic have warmed at over 3 times the global average during the last century and there has consequently been a dramatic decline in the amount of sea ice that survives the summer melt season. The minimum, summer Arctic sea ice extent is currently declining at 13.2% per decade. Predicting the future of Arctic sea ice is critical for understanding global climate change due to the presence of another positive feedback loop: reduced summer sea ice replaces the white, high albedo ice surface with the darker, low albedo, ocean surface. This means that more solar energy is absorbed, raising surface temperatures and increasing ice melt, leading to more exposed ocean and further warming.

Dr Jack Landy has used remote sensing data from satellites, including CryoSat-2 and ICESat, to measure the roughness of Arctic sea ice and to model the impact that changing roughness has on albedo (see Figure 3). The roughness of the sea ice controls the size of the meltwater ponds that can form on the surface. With less sea ice lasting through multiple summer melt seasons, the trend is for Arctic sea ice to become smoother, allowing larger and larger ponds to form which, again, have a lower albedo than the ice surface they sit on, creating yet another positive feedback loop [3].

Figure 3: Panels a and b are predictions for summer (June to August) Arctic sea ice albedo based upon ice roughness observations made in March of 2005 and 2007 respectively. Panels c and d show the actual, observed summer albedo in those years. Image credit: Dr Jack Landy [3].

Mountain glaciers

A third element of the cryosphere studied at the BGC are glaciers in high mountain regions such as the Andes and the Himalayas. Led by Professor Jemma Wadham, the new Director of the Cabot Institute, this work focuses on the biology and chemistry of the meltwater produced from these glaciers. This summer a team of postgraduate researchers from the BGC – Rory Burford, Sarah Tingey and Guillaume Lamarche-Gagnon – travelled to the Himalayas in partnership with Jawaharlal Nehru University, New Delhi, to collect meltwater samples from the streams emanating from the Chhota Shigri glacier. These streams eventually flow into the Indus river, a vital water source for agriculture and industry in Pakistan. It is therefore crucial to understand how the quality of this water source might change in a warmer climate. Mercury, for example, is precipitated out of the atmosphere by snowfall and can collect and become concentrated within these high mountain glaciers. In the shorter term, if these glaciers continue to melt more rapidly, larger amounts of mercury will be released into the environment and will impact the quality of water that supports millions of people. On longer time scales, the retreat and reduction in volume of the Himalayan glaciers will reduce the amount of water supplied to communities downstream, with huge implications for water security in the region.

Figure 4: Photo from Himalayan fieldwork. Image credit: Guillaume Lamarche-Gagnon


This is just the tip of the BGC research iceberg, with field data from this summer currently being pored over and new questions being developed. This work will hopefully inform the upcoming IPCC special report on the oceans and cryosphere (due in 2019), which is set to be another significant chance to assess and share our understanding of the ice on our planet and what it means for the challenges we have set for ourselves in tackling climate change.


[1] Dawson, G. J., & Bamber, J. L. (2017). Antarctic grounding line mapping from CryoSat‐2 radar altimetry. Geophysical Research Letters, 44, 11,886–11,893.

[2] Williamson, C. J., Anesio, A. M., Cook, J., Tedstone, A., Poniecka, E., Holland, A., Fagan, D., Tranter, M., & Yallop, M. L. (2018). ‘Ice algal bloom development on the surface of the Greenland Ice Sheet’. FEMS Microbiology Ecology, 94,3.

[3] Landy, J. C., J. K. Ehn, and D. G. Barber (2015). Albedo feedback enhanced by smoother Arctic sea ice. Geophysical Research Letters, 42, 10,714–10,720.

This blog was written by Cabot Institute member Tom Mitcham. He is a PhD student in the School of Geographical Sciences at the University of Bristol and is studying the ice dynamics of Antarctic ice shelves and their tributary glaciers.

Tom Mitcham

Read other blogs in this Green Great Britain Week series:
1. Just the tip of the iceberg: Climate research at the Bristol Glaciology Centre
2. Monitoring greenhouse gas emissions: Now more important than ever?
3. Digital future of renewable energy
4. The new carbon economy – transforming waste into a resource
5. Systems thinking: 5 ways to be a more sustainable university
6. Local students + local communities = action on the local environment