Constraining Arctic Carbon-Cycle Feedbacks

Arctic permafrost covers a vast area of the Earth, more than 60 times the size of the UK, where temperatures are so low that the ground is frozen year-round. This means that the soil has a memory: plants and animals that lived thousands of years ago and were buried in the soil have remained frozen there, without fully decomposing. This has continued over time, and huge stores of organic matter have built up in the ground. Permafrost forms a solid layer, causing water-logging at the surface, which also stops the organic matter from decomposing.

Global warming has started to thaw the permafrost, and this is set to continue. As the soil thaws, microbes start to decompose the previously-frozen and waterlogged organic matter, turning it into greenhouse gases: carbon dioxide and methane. In total, there is more carbon in Arctic soils than in the whole atmosphere, which gives the potential for massive release of greenhouse gases from thawing permafrost. This means any warming caused by humans may be amplified by extra greenhouse gases from the permafrost. Understanding the global warming impact from permafrost emissions is therefore crucial in determining whether we can meet international climate targets, such as those in the Paris agreement.

Studies show that greenhouse gas emissions from permafrost could cause up to 0.8C additional global warming by the end of the century. However, this figure is highly uncertain and further research is required to understand the mechanisms involved. My project would address vital unanswered questions: How much of the organic matter in the soil will decompose, and how quickly? How much global warming will it cause? Will plants grow better in a warmer Arctic, and does this compensate for the greenhouse gases released from permafrost?

I will study global patterns to determine how Arctic soils might look in warmer climates. Soils without permafrost tend to store less organic matter than Arctic soils. By analysing how the organic matter is related to factors like air temperature and rainfall on a global scale, I will develop a new way to estimate soil organic matter. Then, using predictions of future climate from the latest climate models, I will estimate how organic matter in the Arctic will change under global warming, and from this, approximately how much greenhouse gas would be released.

I will then work with field measurements to develop a sophisticated model to simulate the future of the Arctic. JULES is part of the UK's climate model; it's a model of the land surface of the whole Earth. I would incorporate key processes that are currently not included in the JULES model, resulting in a new model version capable of simulating the most important Arctic processes. Based on the latest scientific understanding from new measurements in the Arctic, I would develop innovative schemes to represent: 1) Water distribution (including waterlogging) in permafrost soils, 2) Arctic plant species, 3) decomposition of organic matter in the soil.

The future is always uncertain, which means that it is not possible to put an exact value on future greenhouse gas emissions from the Arctic, but rather to give a range of values. I will approach this using mathematical techniques that translate the information contained in observations into a range of uncertainty within the JULES model itself: Essentially answering the question, if data gives us a certain amount of information about the real world, what is the range of possible models that is consistent with this? I will then run simulations with the full range of models to estimate the full set of possible futures. This will simulate the major changes in the Arctic over the next century: thawing permafrost, shifting vegetation, and exchanges of carbon dioxide and methane from the land surface.

Ultimately this will lead to a more robust understanding of the greenhouse gas balance in the Arctic, and the role of the Arctic in global climate change.

The main beneficiaries of this research would be:
1) UK research organisations
2) Policy-makers
3) General public
4) My career development
5) Arctic industries and communities

1) UK research organisations

Both the Centre for Ecology and Hydrology and the Met Office develop and make use of the JULES land surface model, as part of their remit and activities. This includes activities such as assessments of long-term climate change (running JULES as part of UKESM), climate impacts on land-based resources, and flood risk forecasting. The developments to JULES made during the fellowship project would improve the simulation of hydrology in the model, which would benefit, for example, flood forecasting and impacts assessments. The global carbon cycle simulation would also be majorly improved, which would contribute to improved projections of long-term climate change.
I have worked closely with the Met Office since 2013. By visiting weekly I have been able to contribute to JULES developments, testing and code reviewing as part of in-house activities. We would both continue to benefit from ongoing interaction.

2) Policy-makers

This project would quantify feedbacks on climate change due to Arctic carbon-cycle dynamics, which would help to better constrain the impact of anthropogenic greenhouse gas emissions on global warming. This would benefit the work of organisations seeking to inform governments and policy-makers about the impacts of anthropogenic emissions on climate change, and the development of policies for climate-change mitigation. This is particularly relevant for the United Nations Framework Convention on Climate Change (UNFCCC), which brings together all UN countries to develop and work towards climate-change mitigation targets. My work would be beneficial for the Intergovernmental Panel on Climate Change, which produces policy-relevant syntheses of the latest scientific understanding on climate change, in turn informing governments and the UNFCCC. The UK government would also directly benefit via regular reporting by the Met Office.

3) General public

This project would contribute towards public awareness of environmental and Arctic issues. Communicating the science will inspire people both by giving insight into the 'human' side of research, at the same time as exciting new scientific developments. Outcomes of the project would include online media, such as blogging and a project-specific website. (This was shown to be very popular during the PAGE21 project, where the blogs received large numbers of pageviews.) I would aim to publish my work in generalised journals such as Nature Climate Change, which would ensure that it is presented in an accessible format and receives wide media coverage, reaching a large number of people. Educating and inspiring young people about science is crucial for the future, and this would be achieved through continued outreach projects (including through 'Exeter Community Climate Network' and projects with local schools).

4) My career development

This project will further develop the scope of my research skills, particularly in model optimisation and fieldwork techniques. It would enable me to develop my leadership skills through supervising a PhD student, and provide me with a unique opportunity to start my independent research group. With the models developed in this Fellowship I will develop new international collaborations through exchange visits (e.g. in the US/Canada). These models will also provide a basis for my future grant applications, allowing me to recruit PDRAs to my research group.

5) Arctic industries and communities

Future beneficiaries include industries with infrastructure in the Arctic - such as oil pipelines - and Arctic communities. These groups would benefit from improved projections of permafrost thaw that will result from this project, which indicate regions vulnerable to ground collapse.