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

Posted on October 15, 2018April 13, 2023 by janet.crompton

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, www.AntarcticGlaciers.org

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

Outlook

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.

References

[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. https://doi.org/10.1002/2017GL075589

[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. https://doi.org/10.1093/femsec/fiy025

[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. https://doi.org/10.1002/2015GL066712

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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

Your Waste of Time: Art-Based Geographical Practices and the Environment

Posted on August 25, 2017April 5, 2023 by janet.crompton

This blog post thinks through the themes of aesthetic interventions, sensing time and engendering response-ability using artistic responses to climate change. Here, these themes are drawn from one piece of art, Your Waste of Time, by Danish-Icelandic artist Olafur Eliasson. This performative showcasing of glacial ice establishes interactions and relations between human bodies and icy materialities- but what is at stake here and what potentialities could be created through artistic practices? These are questions that have arisen through my current dissertation, where I hope to explore artistic responses to environmental degradation through the materialities of ice and plastic.

For the piece Your Waste of Time, Danish-Icelandic artist Olafur Eliasson transported several large blocks of ice from Vatnajökull, the largest and oldest glacier in Iceland, to the Berlin gallery Neugerriemschneider (Eliasson, 2006). This glacier is almost incomprehensibly ancient, with some parts dating from around 1200 AD, but human-driven global warming has begun thawing Vatnajökull, dislodging chunks of ice from the main body of the glacier. This has left behind a scattering of sculpture-like nuggets of ice across the landscape, pieces that untouched, would soon melt away. Eliasson’s project transported these pieces to Germany, to be displayed in an art gallery.

Here the wayfaring blocks of ice were kept in a refrigerated space as immersive sculptures that audience members were encouraged to touch. This was an attempt by Eliasson to bring the visceral reality of human-driven climate change to the attention of the audience through a sensory engagement with ice. In Eliasson’s words, ‘we take away time from the glacier by touching it’ (Eliasson, 2006). Within this molecular moment of sensation between the human and icy touch, the exchange of human warmth is enough to begin to decay the ice. Your Waste of Time then becomes an experiment to curate a sense of environmental care through molecular icy interactions.

Your Waste of Time, Olafur Eliasson, photo by Jens Ziehe

Recently, such environmental artistic interventions have been located temporally with the term ‘anthropocene’[1]. Anthropocene has come into use to refer to human-driven environmental change and degradation. Although the ‘Anthro-pocene’ privileges and homogenises the human (a white, western human) within environmental discourses, the term has become a buzzword for the current era of global pollution and warming. As an imaginary, the Anthropocene cuts through different temporalities; finite human lives, longer lived materialities (such as ice) and geological timescales.

Artistic responses to environmental issues engage with this increasingly unpredictable world, through a sensory engagement with temporality, with other materialities and bodies. It can even be said that ‘attuning ourselves, through poetry, art, and description, to pay attention to other times…these are crucial practices; in fact, they are matters of survival.’ (Davis and Turpin, 2015). Although influential feminist scholar Donna Haraway (2015) proposes other terms such as Capitalocene to denote the specifically capitalist causes of environmental degradation, the Anthropocene also remains an arguably productive term. Art positioned as relating to different temporal imaginaries is thus a speculative, experimental project to think differently, to world differently. Although the term Anthropocene remains contestable, it’s very instability lends itself to artistic conceptual engagements that function through such fragile and indeterminate encounters.

Image: Your Waste of Time, Olafur Eliasson, photo by Jens Ziehe

Positioned in the white, empty space of the art gallery, the fragility of the ice is magnified. This fragility comes to light through the invocation to touch the surface of the icy sculpture. In the words of Eliasson; ‘When we touch these blocks of ice with our hands, we are not just struck by the chill; we are struck by the world itself. We take time from the glacier by touching it’. As Erin Manning (2006), notes in her work on the intersections between art practice and philosophy, sensation opens up the body to thinking and doing differently through its relation to other bodies and things. Touch, in this light, is located neither with the human or the inhuman, but invented through the encounter.

But what happens at a touch? Ice, as sensory aesthetic experience, brings closer together the relations already held between ice and human bodies. Quantum physicist turned feminist philosopher Karen Barad (2012) brings together feminist traditions that unsettle ways of thinking materiality and quantum physics. A sense of touch, for Barad, can be unsettled a molecular exposition of the minute interactions between electrons. This is a murky and confusing world of quantum physics for most social scientists, but Barad productively draws out the indeterminacy at the very building blocks of sensation. Quantum theory holds infinites as integral. This argues for a radical openness of potentialities at the very building-blocks of mattering – all matter is unstable at its foundations. Could it be argued that there is at stake, the unsettling of stable ways of thinking and an opening up of openness already at the heart of mattering?

At the moment of touch between a hand and the blocks of ice, this becomes clear- the warmth of the body causes the ice to change state and start to melt. For Eliasson, ‘We take away time from the glacier by touching it. Suddenly I make the glacier understood to me, its temporality. It is linked to the time the water took to become ice, a glacier. By touching it, I embody my knowledge by establishing physical contact. And suddenly we understand that we do actually have the capacity to understand the abstract with our senses. Touching time is touching abstraction.’ What does it mean to touch time? Touch, as unsettling and in-touch with infinite possibilities could signal a potential for thinking differently. The term anthropocene signals (if problematically) this need to think differently about temporality. The geologic lifespan of the ice is not permanent, but made fragile under a human touch. Temporality, then is not a stable concept either, but one that aesthetic interventions can trouble and disrupt assumptions that time related solely to a stable ticking of the clock.

This touching-time, for Eliasson, has a political undertone. Time is a crucial and sensitive issue in climate change debates. The critical question is, how to engender response-ability and action to do something to halt the tide of environmental degradation and global temperature rise. Haraway (2015) has written about an art project by the Institute of Figuring (2005-ongoing) to crochet coral reefs, involving thousands of people working to cultivate and care for these crochet-corals, gathering each person’s work into an exhibition, curating the corals to establish a reef. Like Your Waste of Time, The Crochet Coral Reef Project has time at its centre. Crocheting, like the establishment of a coral reef, takes time, and has the potential to establish caring relations through the touch of human-material and time. Could art such as this create publics that could do differently concerning climate change?

Image: Crochet Coral Reef Project, Institute of Figuring

Care in this context relates to everything that both humans and nonhuman things to continue to repair their world to live as well as possible. These caring relations knit the world together and create complex links between things and humans in the world. Feminist scholar Puig de la Bellacasa (2011) proposes an ethics of care. This care is not a moralism. It is not a case of you should care about environmental degradation! Rather, it is a speculation to see what could happen if we relate to the things and environments around us through more caring relations.

Your Waste of Time, framed through touch, time and care touches upon possible pasts, presents and futures that are framed as undecided. As the ice hovers indeterminately in-between solid and liquid, so does the potential for doing differently. Geologic timescales interact with a momentary present. Could this moment of touch between ice and human engender more caring relations that span other times and other places? Your Waste of Time, then, may not be a waste of time, but rather put us in-touch with time.

Blog by Rosie McLellan

Reposted from ‘Bristol Society and Space‘ Blog of the University of Bristol’s MSc in Human Geography

Bibliography
Barad, K. (2012) ‘On touching – The inhuman that therefore I am’, Differences, 23(3): 206-223
Davis, H. and Turpin, E., eds. (2015), ‘Art in the Anthropocene’, London: Open Humanities Press
De la Bellacasa, M. (2011), ‘Matters of care in technoscience: Assembling neglected things’, Social Studies of Science, 41(1): 85-106
Eliasson, O. (2006), ‘Your Waste of Time’, Berlin: Neugerriemschneider [http://olafureliasson.net/archive/artwork/WEK100564/your-waste-of-time]
Haraway, D. and Kenney, M. (2015), ‘Anthropocene, Capitolocene, Chthulhocene’, in: Davis, H. and Turpin, E., eds. (2015), ‘Art in the Anthropocene’, London: Open Humanities Press
Institute of Figuring, (2005-Ongoing), ‘Crochet Coral Reef Project’, New York: MAD Museum of Modern Arts [http://madmuseum.org/exhibition/crochet-coral-reef-toxic-seas]
Manning, E. (2006), ‘Politics of Touch: Sense, Movement, Sovereignty’, Minneapolis: University of Minnesota Press

See more regarding the Anthropocene at https://www.theguardian.com/environment/2016/aug/29/declare-anthropocene-epoch-experts-urge-geological-congress-human-impact-earth

If we burned all fossil fuels, would any of Antarctica’s ice survive?

Posted on September 14, 2015April 13, 2023 by janet.crompton

Andy Ridgwell, University of California, Riverside

Here is a great “what-if”: if we (the human race) were to burn all available fossil fuels, could we melt the largest and most stable ice sheet on the planet – Antarctica? Could our collective industrial impacts on the planet possibly have that far a reach?

The spoiler is: “yes,” although in our recent computer modeling-based study, we find that it would require all of our fossil fuel resources to do it, and to see the very last of the ice melt, we might have to wait as long as 10,000 years.

Before we get any further, let’s consider this as a thought experiment in ice sheet dynamics and the global carbon cycle response to CO2 emissions to test our understanding of the long-term effects that extreme perturbations could have on the Earth system.

What I have in mind is a socioeconomic carbon use scenario that I hope personally would never come to fruition, but equally one that is not intended to be an implausible scare story or a “sky is-falling-in” simulation of doom and gloom and future global environmental catastrophe. (And also, to be completely honest, it was not my thought experiment in the first place, but instead comes from the head of Ken Caldeira at the Carnegie Institution for Science, Stanford, who was very ably assisted in bringing it to fruition by a brace of ice-sheets modelers at the Potsdam Institute for Climate Impact Research in Germany – Ricarda Winkelmann and Anders Levermann.)

However, given unrestrained burning of fossil fuels, our study does show that the largest mass of ice in the world, including both the East and West Antarctica ice sheets, ultimately is vulnerable to irreversible melting – and dramatic sea-level rise.

Lessons from the past?

We already know that the Antarctic ice sheet has not always been there, and there is abundant geological evidence that around 50-100 million years ago, sea surface temperatures around Antarctica were pleasantly warm and vegetation on the Antarctic Peninsula was lush and warm-temperature. (And yes, prior to 65 millions years ago, there were dinosaurs living there too.) Our best reconstruction of atmosphere CO2 at the time is somewhere in the region of 556-1,112 parts per million (ppm) and higher than the almost 400 ppm we have reached today.

How Antarctic ice would be affected by different emissions scenarios. GtC stands for gigatons of carbon.
Ken Caldeira and Ricarda Winkelmann, Author provided

But this does not provide a particularly helpful guide to future ice sheet susceptibility. These past warm climates represent intervals of millions of years of elevated atmospheric CO2, whereas in the future, CO2 levels will start to drop back down once fossil fuel emissions cease. And this brings us to the crux of the problem, at least from my perspective: just how quickly will CO2 decay back down toward 278 ppm, the preindustrial atmospheric concentration?

The ‘long tail’ of CO2

There are a variety of processes that will act to progressively remove CO2 from the atmosphere, starting with uptake by the ocean and the terrestrial biosphere, occurring on timescales of up to 1,000 years. There are also a series of geological processes, involving first reactions of carbonic acid (CO2 dissolved in water) with calcium carbonate minerals in chalks and limestones and then ultimately, the gradual dissolution of silicate rocks such as granites and basalts over hundreds of thousands of years.
Can the ocean absorb enough CO2 before too much ice melt occurs? What about the geological processes – are these really too slow to help in time even under a much warmer climate and faster weathering rates?

This map shows the changes to coastlines if sea level rose six meters. Recent projections show that continued fossil fuel use over the next 1,000 years will lead to sea-level rise of 100 feet.
NASA, CC BY

Without access to a time machine, I constructed numerical models that incorporate as many of the key processes of the global carbon and climate system as is feasible. To run a model to simulate many thousands of years, I must leave out many of the atmospheric physical processes, but the basic CO2 response is carefully tested and relatively independent of the omission of monsoons and El Ninos and all the complex short-term dynamics of the real climate system.

We then ran the model forced by a wide range of possible CO2 emissions scenarios, from 1,000 gigatons of carbon to 10,000 gigatons. To date, people have cumulatively emitted close to 600 gigatons, so we are easily on track to soon exceed the minimum assumption we tested in the study.

The tail wagging the climate dog

Even before considering the Antarctic ice sheet response, an unexpected result emerges – once enough CO2 is emitted to the atmosphere, climate almost gets “stuck” in a warm state that persists for the ~8,000 years until the end of the model experiment.

There are two things at play here: first, the more carbon we emit to the atmosphere, the less effective the ocean is in absorbing it. Basically, at some point, the main mechanism by which the ocean absorbs CO2, which is chemical reaction with carbonate ions (CO32-), gets maxed out (in other words: there are no more carbonate ions left to react with). This is also the way in which ocean acidification occurs. A warmer ocean doesn’t help, as CO2 is less soluble at higher temperatures and prefers to stay in the atmosphere. What about the geological sinks? Yes, they are working hard, and atmospheric CO2 does decline in all experiments, but just not quickly enough to avoid large-scale melting in Antarctica.

The second thing concerns the underlying nature of the relationship between climate and CO2.
Per molecule, CO2 becomes progressively less effective at trapping outgoing heat (infrared radiation) the more molecules that are already there. For society, this is a good thing: instead of each gigaton emitted having the same additional climatic impact, you have to approximately double the excess CO2 in the atmosphere to raise the surface temperature by the same amount each time – a log relationship. In our experiments, we see the flip side of this in response to the highest carbon emissions scenarios. Because we require a halving of CO2 to give us the same cooling each time, surface temperature declines even slower than CO2 concentrations.

In a nutshell: if we were to burn all fossil fuel reserves, the Antarctic ice sheet is threatened in its entirety, principally because we break the ability of the ocean and other natural mechanisms to bring atmospheric CO2 concentrations down fast enough.

Ice loss and sea-level rise

The future climate patterns we simulated then drove the ice sheet model, which is absolutely key and is as carefully tested as any of the other model components used in our study.

As expected from previous work, for low-emissions scenarios, the ice sheet actually gains mass due to increased snowfall over the coming century. However, on the long term, it is the surface warming and associated melt that dominates the mass balance.

And as the ice sheet melts, things go from bad to worse: surface temperatures get warmer as the elevation of the ice sheet falls, and sea-level rise increasingly helps to destabilize the ice sheet from below.

The rest is history. Or need not be. I hope that consuming as much as 10,000 gigatons of fossil fuel carbon is unlikely. But we also found that sea level progressively creeps up once we look beyond the end-of-century focus where much of the climate change debate is focused, for all scenarios. Even for really rather moderate carbon releases, sea level could rise 5-10 meters, or about 15-30 feet, by the end of the millennium.

Hence, a genuinely plausible scenario is that the world’s coastline in 50-100 generations’ time is going to look very different. Now is the time to invest in far inland “beachfront” real estate for your great-great-great-…-great-grandchildren.

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This blog was written by Andy Ridgwell, Professor of Earth System Science, University of California, Riverside and member of the University of Bristol’s Cabot Institute.

This article was originally published on The Conversation. Read the original article.

Weathermen of Westeros: Does the climate in Game of Thrones make sense?

Posted on July 2, 2015April 13, 2023 by janet.crompton

The climate has been a persistent theme of Game of Thrones ever since Ned Stark (remember him?) told us “winter is coming” back at the start of season one. The Warden of the North was referring, of course, to the anticipated shift in Westerosi weather from a long summer to a brutal winter that can last for many years.

An unusual or changing climate is a big deal. George R R Martin’s world bears many similarities to Medieval Europe, where changes to the climate influenced social and economic developments through impacts on water resources, crop development and the potential for famine.

We’re interested in whether Westeros’s climate science adds up, given what we’ve learned about how these things work here on Earth.

It’s not easy to understand the mechanisms driving the climate system given we can’t climb into the Game of Thrones universe and take measurements ourselves. It’s hard enough to get an accurate picture of what’s driving the world’s climate even with many thousands of thermometers, buoys and satellite readings all plugging data into modern supercomputers – a few old maesters communicating by raven are bound to struggle.

The fundamental difference between our world and that of Westeros is of course the presence of seasons. Here on Earth, seasons are caused by the planet orbiting around the sun, which constantly bombards us with sunlight. However the amount of sunlight received is not the same throughout the year.

You won’t see this in Westeros. Rhcastilhos

If you imagine the Earth with a long pole through its centre (with the top and bottom of the pole essentially the North and South Pole) and then tilt that by 23.5 degrees, the amount of sunlight received in the Northern and Southern Hemispheres will change throughout the year as the Earth orbits the Sun.

Clearly the unnamed planet on which Game of Thrones is set is missing this axis tilt – or some other crucial part of Earth’s climate system.

How longer seasons might work

The simplest explanation could be linked to spatial fluctuations in solar radiation (sunlight) received at the surface. A reduction in incoming solar radiation would mean more snow and ice likely remaining on the ground during the summer in Westeros’s far north. Compared to the more absorbent soil or rock, snow reflects more of the Sun’s energy back out to space where in effect it cannot warm the Earth‘s surface. So more snow leads to a cooler planet, which means more snow cover on previously snow-free regions, and so on. This process is known as the snow albedo feedback.

The collapse of large ice sheets north of the Wall could also rapidly destabilise ocean circulation, reducing northward heat transport and leading to the encroachment of snow and ice southwards towards King’s Landing.

What if all this ice suddenly melted? HBO

To descend into glacial conditions would require a large decrease in solar radiation received at certain locations on the Earth’s surface and likewise an increase would be needed to return to warmer conditions.

This is roughly what happened during the switches between “glacial” and “interglacial” (milder) conditions throughout the past million years on Earth. This is controlled primarily by different orbital configurations known as “Milankovitch cycles”, which affect the seasonality and location of sunlight received on Earth.

However, these cycles are on the order of 23,000 to 100,000 years, whereas Game of Thrones seemingly has much shorter cycles of a decade or less.

When winter came back

Around 12,900 years ago there was a much more abrupt climate shift, known as the Younger Dryas, when a spell of near-glacial conditions interrupted a period of gradual rewarming after the last ice age peaked 21,000 years ago. The sudden thawing at the end of this cold spell happened in a matter of decades – a blink of an eye in geological terms – and led to the warm, interglacial conditions we still have today.

A particularly long and brutal winter? Younger Dryas
cooling is visible in Greenland ice core records. NOAA

Various different theories have tried to explain why this spike occurred, including the sudden injection of freshwater into the North Atlantic from the outburst of North American glacial lakes, in response to the deglaciation, which destabilised ocean circulation by freshening the water and reducing ocean heat transport to the North Atlantic Ocean, cooling the regional climate.
Less likely explanations include shifts in the jet stream, volcanic eruptions blocking out the sun, or even an asteroid impact.

The shift from the Medieval Warm Period to the Little Ice Age that began around 1300 AD represents a more recent, and more subtle, example of a “quick” climate change. Although the overall temperature change wasn’t too severe – a Northern Hemisphere decrease of around 1˚C compared with today – it was enough to cause much harsher winters in Northern Europe.
None of these events indicate the abrupt transitions from long summers to long winters as described in Game of Thrones – and they still all happen on a much longer timescale than a Westeros winter. However they do demonstrate how extreme climate shifts are possible even on geologically short timescales.

Regardless of the causes of the long and erratic seasons, winter in Westeros won’t be much fun. It may even make the struggle for the Iron Throne between the various factions seem irrelevant.
Indeed the House of Stark’s motto: “winter is coming” may have a lesson for us here on Earth. Anthropogenic climate change is one of the biggest challenges facing humankind today and if left unmitigated the potential environmental impact on society may be far greater than any global recession. Stop worrying about the Iron Throne, everyone, winter is coming.
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This blog has been written by Cabot Institute members Alex Farnsworth, a Postdoctoral Research Assistant in Climatology at University of Bristol and Emma Stone, a Research Associate in Climate History at University of Bristol.

This article was originally published on The Conversation. Read the original article.

Life on the ice: Fieldwork in Antarctica

Posted on February 18, 2015April 14, 2023 by janet.crompton

From early November last year, I was lucky enough to spend over two months doing fieldwork on Pine Island Glacier, an ice stream in West Antarctica, which is currently the largest single contributor to sea level rise. I was part of a twelve person team that made up the second iSTAR traverse.

iSTAR is a collaborative scientific programme, funded by the Natural Environment Research Council (NERC) and co-ordinated by the British Antarctic Survey (BAS). It aims to improve our understanding of the stability of the West Antarctic Ice Sheet, which could potentially undergo rapid retreat in the coming centuries. It is divided into two halves – half the programme is ocean focused, looking at how relatively warm Circumpolar Deep Water intrusions onto the continental shelf interact with the ice shelves in the Amundsen Sea. The University of Bristol is involved in the second half of the programme, which is concerned with the ice sheet dynamics and mass balance, particularly the changes happening to Pine Island Glacier (PIG). In order to study these changes, two traverses of PIG have been made, over two consecutive seasons (2013-14 and 2014-15). The 800 km traverse, took in 22 sites across the ice stream and its tributaries, where various scientific techniques were used to determine the properties of the ice, glacier bed and firn layer (compacted snow).

During this season, despite some strong winds, we successfully completed all the science we set out to do, included seven seismic surveys, ten shallow ice cores, 22 neutron probe snow density profiles and ten phase-sensitive radar profiles. For me, as a PhD student, it was a great experience to work with senior scientists in the field, and to be involved in such a wide range of field techniques.

The scientific goals of the iSTAR traverse could not been achieved without the use of the traverse logistics, which involved using Pisten Bully snow tractors to tow the caboose (a converted container that acts as kitchen and living space), equipment and fuel from site to site. This is a new way of field operation for BAS and is likely to feature in many more scientific programmes in the future, given the success of the two iSTAR traverses. Of course, there are some old-school field scientists who joke that we are the Caravan Club of Antarctica, but I think they are just jealous – eating pancakes for breakfast in the caboose has to beat sitting in a pyramid tent eating rehydrated rations!

On the move! Image credit: Isabel Nias

Despite the perhaps more luxurious living conditions than the average field party, living in the deep field on the ice was not without its challenges. We were still sleeping in tents and my standard answer to the question, “but how did you wash?” has been, “I didn’t”. At the beginning of the field season we had temperatures as cold as -35°C (plus wind chill), which froze your breath inside your nostrils. However, I preferred the cold to the “warm” temperatures we had towards the end of the field season (it hit 0°C at one point!), which made our boots and gloves all damp. The work was also physically hard. Each seismic survey was 7 km long, and involved a team of us drilling 30 hot water drill holes, which were then loaded with explosives, and digging over 700 holes to place the geophone sensors in the snow. Although it was worth it for the end product: an idea of the type of bedrock PIG is flowing over.

Before I arrived, I had heard from Steph Cornford, who was on the first iSTAR traverse, that the weather had been exceptionally pleasant last year, with plenty of blue skies and low winds. So much so that they ate their Christmas dinner outside! This year, the weather was more like what you would expect from Antarctica – we certainly had our fair share of strong winds, which hindered progress at times, especially due to the sensitivity of the seismic work to wind speed. I got very good at estimating the wind speed based on how much my tent was shaking, or by looking at the Union Jack flying from the caboose!

Emma Smith and Alex Brisbourne (BAS) making their way to the
safety of the caboose on New Year’s Day. Image credit: Alex Taylor.

New Year on PIG was certainly one to remember. We spent the evening doing a pub quiz in the caboose and seeing in the New Year with a whisky and a poor rendition of Auld Lang Syne. By 1:30 am, however, the winds had picked up to 50 knots with gusts of up to 65 knots, creating extreme white out conditions from all the blowing snow. Many of us who were still up decided to sleep in the caboose that night. I’m glad I did because I doubt I would have slept at all in my tent (from the noise and the fear that the tent would be ripped from its pitch!). The strong winds persisted well into New Year’s Day, but we were able to assess the damage. Rather than blowing away, my tent was actually half buried by a huge drift. However, it could have been worse – James’ tent was destroyed and completely filled with snow! It took the whole of the next day to get camp cleared again – is “shovelling snow” a worthy thing to put on my CV?

Looking back, it is not working until 3 am to finish a seismic line that I remember. Rather, it is the people, as well as all the amazing experiences I had, which stick in my mind. It’s not every day that you co-pilot a plane across West Antarctica or bake a Christmas cake on 1800 m thick ice.

I would like to thank iSTAR, BAS and all the guys at the Rothera Research Station for such an awesome experience. The real work starts now – we have a lot of data to work on! Have a look on the iSTAR website for more blog posts written while we were in the field.

The second iSTAR traverse team at Christmas, complete with a ratchet strap Christmas tree. Image credit: Alex Taylor

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Cabot Institute member Isabel Nias is a PhD student in the Bristol Glaciology Centre, School of Geographical Sciences at the University of Bristol. Her PhD, which is funded through the NERC iSTAR programme, aims to use ice flow modelling to understand the sensitivity of the Amundsen Sea ice streams, and their potential impact on future sea level rise.

Isabel Nias

The controversy of the Greenland ice sheet

Posted on March 17, 2014April 19, 2023 by janet.crompton

I was expecting a dusty road, a saloon door swinging, two geologists standing facing each other in spurrs and cowboy hats with their hands twitching at their sides, both ready to whip out their data and take down their opponent with one well-argued conclusion.

Sadly (for me), things were much more friendly at Professor Pete Nienow‘s seminar in Bristol’s Geographical Sciences department last week. Twelve years ago he visited the University with a controversial hypothesis, causing considerable debate with members of the department. Now he was back, Powerpoint at the ready, to revisit the theory.

Professor Nienow is a glaciologist at the University of Edinburgh. He is currently researching glacial movement and mass in Greenland, but I’ll let him tell you more.

Pete Nienow – GeoScience from Research in a Nutshell on Vimeo.

The Greenland ice sheet covers almost 80% of the country, enclosed by mountains around its edges. The ice sheet is dynamic; glaciers are constantly moving down from the summit towards the sea but replaced each winter by snow. Glaciers are funnelled through the mountains in large “outlet glaciers” that either melt or break into icebergs when they reach the sea.

There is plenty of evidence to suggest that the outlet glaciers are speeding up, rushing down to meet the sea almost twice as fast as they did in the 1970s. Unfortunately that means more melting icebergs floating around, contributing to sea level rise. The winter snowfall is not able to replenish this increased loss of glacial mass, so the Greenland ice sheet is slowly shrinking.

Coverage of the Greenland ice sheet in different future climate change scenarios. A critical tipping
point could be reached, after which it will be impossible to stop the ice from melting and raising sea
levels by seven metres globally. Source: Alley et al., 2005 (Science)

Controversy

Professor Nienow stirred up a debate in 2002, when he proposed that the Zwally Effect could be hugely important for the Greenland ice sheet. This theory suggests that meltwater could seep down through the glacier to the bedrock, lubricating and speeding up the glacial movement.

The conventional wisdom of the time was that it would be impossible for meltwater to pass through the 2km of solid ice that comprises most of the Greenland ice sheet. The centre of the glacier is around -15 to -20°C, so the just-above-freezing water would never be able to melt its way through.

Meltwater research

Meltwater on glaciers often pools on the surface, creating supraglacial lakes. These lakes can drain slowly over the surface, but Professor Nienow found that they can disappear rapidly too. The water slips down through cracks in the ice to the bedrock, leading to a rapid spike in the amount of meltwater leaving the glacier.

Supraglacial lake.
Source: United States Geological Survey, Wikimedia Commons

Meltwater can reach the base of the glacier so that’s one point to Nienow, but can this actually affect the movement of the glacier?

During the summer, the higher temperatures lead to increased glacial melting, which drains down to the bedrock. This raises the water pressure under the glacier, forcing it to slide more rapidly. Interestingly, as the season progresses, Nienow found that the meltwater forms more efficient drainage channels beneath the glacier, stabilising the speed of the ice.

Nienow was almost ready to mosey on back to Bristol, show them how subglacial meltwater had clear implications of glacier loss for a warmer world, and declare himself the Last Geologist Standing.

Turning point

Glaciologists had always assumed that the winter glacier velocity was consistently low. However, at the end of a very warm 2010, Nienow and his colleagues discovered a blip of especially low speeds, even slower than the standard winter “constant”.

The large channels underneath the glaciers formed by the extra meltwater of that hot year actually reduced the subglacial water pressure during the winter, slowing the glacier more than on a normal year. Nienow found that this winter variability is critical for overall glacier velocity and displacement. In 2010, the net effect of both summer and winter actually meant that the glacier velocity was reduced in this hot year.

Back to Bristol

Nienow returned to Bristol to give his seminar. Somewhat unlike a cowboy film, Nienow concluded that it was a draw; he’d been right that it was possible for meltwater to seep down to the bedrock and lubricate glacial movement, but his friends at Bristol had been correct in thinking that it wasn’t very important in the grand scheme of things.

A collaborative paper between Professor Nienow, the Bristol team and other glaciologists from around the world found that subglacial meltwater will only have a minor impact on sea level rise, contributing less than 1cm of water globally by 2200. Surface run off and the production of icebergs will continue to play a bigger role, even in a warming world. The computer models used to predict sea level rise will be able to include these findings to give a more accurate insight into future glacier movement and coverage across Greenland and beyond.

Bristol glaciologist Dr. Sarah Shannon, lead author on the paper, pointed out that whilst overall glacier velocity is unlikely to be affected by subglacial meltwater in warm years, “global warming will still contribute to sea level rise by increasing surface melting which will run directly into the ocean”.

This blog is written by Sarah Jose, Cabot Institute, Biological Sciences, University of Bristol

You can follow Sarah on Twitter @JoseSci

Sarah Jose