Skip to main content

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, 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

--------------------------------
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

Popular posts from this blog

Powering the economy through the engine of Smart Local Energy Systems

How can the Government best retain key skills and re-skill and up-skill the UK workforce to support the recovery and sustainable growth? This summer the UK’s Department for Business, Energy and Industrial Strategy (BEIS) requested submission of inputs on Post-Pandemic Economic Growth. The below thoughts were submitted to the BEIS inquiry as part of input under the EnergyREV project . However, there are points raised here that, in the editing and summing up process of the submission, were cut out, hence, this blog on how the UK could power economic recovery through Smart Local Energy Systems (SLES). 1. Introduction: Factors, principles, and implications In order to transition to a sustainable and flourishing economy from our (post-)COVID reality, we must acknowledge and address the factors that shape the current economic conditions. I suggest to state the impact of such factors through a set of driving principles for the UK’s post-COVID strategy. These factors are briefly explained belo

Farming in the Páramos of Boyacá: industrialisation and delimitation in Aquitania

Labourers harvest ‘cebolla larga’ onion in Aquitania. Image credit: Lauren Blake. In October and November 2019 Caboteer  Dr Lauren Blake  spent time in Boyacá, Colombia, on a six-week fieldtrip to find out about key socio-environmental conflicts and the impacts on the inhabitants of the páramos, as part of the historical and cultural component of her research project, POR EL Páramo . Background information about the research can be found in the earlier blog on the project website . Descending down the hill in the bus from El Crucero, the pungent smell of cebolla larga onion begins to invade my nose. The surrounding land transforms into plots of uniform rows of onion tops at various stages of growth, some mostly brown soil with shoots poking out along the ridges, others long, bushy and green. Sandwiched between the cloud settled atop the mountainous páramos and the vast, dark blue-green Lake Tota, all I can see and all I can smell is onion production. Sprinklers are scattered around, dr

IncrEdible! How to save money and reduce waste

The new academic year is a chance to get to grips with managing your student loan and kitchen cupboards. Over lockdown the UK wasted a third less food than we usually would. This is brilliant, as normally over 4.5 million tonnes of edible food is wasted from UK homes every year. For students, it’s even higher. The average cost of food waste per student per week is approximately £5.25 - that's about £273 per year !  It’s not just our bank accounts that are affected by food waste – it’s our planet too. The process of growing, making, distributing, storing and cooking our food uses masses of energy, fuel and water. It generates 30% of the world’s CO₂ greenhouse gas emissions. The same amount of CO₂ as 4.6 million return flights from London to Perth, Australia! So it makes sense to keep as much food out of the bin as possible, start wasting less and saving more.  Start the new term with some food waste busting, budget cutting, environment loving habits! Here’s five easy ways to reduce