Constraining Arctic Carbon-Cycle Feedbacks

Lead Research Organisation: University of Exeter
Department Name: Mathematics

Abstract

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.

Planned Impact

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.

Publications

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Hugelius G (2020) Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw in Proceedings of the National Academy of Sciences

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Wiltshire A (2021) JULES-CN: a coupled terrestrial carbon-nitrogen scheme (JULES vn5.1) in Geoscientific Model Development

 
Description This award is looking at the emissions of greenhouse gases from natural ecosystems in the Arctic.
It is in early stages but so far we have two key results which both relate to how emissions of greenhouse gases might increase with global warming, and therefore make it even harder for us to reach the Paris Agreement targets. Methane is a powerful greenhouse gas and I have produced a study of its emissions from northern wetlands.
The first key finding shows that while methane emissions will increase with warming and they are more likely to follow the spatial patterns of temperature sensitivity than the sensitivity that is observed on a site level. This means that the impact on future climate will be less than the most extreme predictions but nonetheless significant.
The second finding relates to how much of the soil carbon in total may be emitted as greenhouse gases. There are two factors that control this and we have reduced the uncertainty one one of these: in particular how the residence time (how long the carbon spends in the soil before being emitted) reacts to warming. This we found again not to be extremely temperature sensitive but again to be significantly affected by warming, which can lead to an increase in greenhouse gases in the atmosphere. If we can also reduce uncertainty on the second factor then we will have a very important and useful result.
A new methodology for modelling methane emissions has been developed which will be of benefit to the modelling community.
Exploitation Route The results regarding methane emissions may already be useful to policy makers (the rest of the work in the project still requires further development before it could be used outside of the science community). In order to realise this impact we could recalculate the carbon budgets based on our existing methodology and include this in the Met Office reporting to the UK government as well as presenting it at the COP this year. I will also write up the result on my website.

Within the scientific community, the results will be presented at the next JULES meeting as well as a more general land surface modelling workshop that follows it, in order to share them with the international community.
Sectors Environment,Government, Democracy and Justice

 
Description Improving MOdelling approaches to assess climate change-related THresholds and Ecological Range SHIfts in the Earth's Peatland ecosystems (MOTHERSHIP)
Amount £516,101 (GBP)
Funding ID NE/V018299/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 01/2022 
End 12/2026
 
Title A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil) for northern and temperate peatlands 
Description This is the data (model output from JULES and observational data) used in the paper "A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil) for northern and temperate peatlands" for the resubmitted version after review of the discussion paper in Geoscientific Model Development Discussions (2021) https://doi.org/10.5194/gmd-2021-263. R code is provided that will recreate all of the plots in the paper using the data provided. These data include outputs from the JULES model including developments to represent peat accumulation, and observational data of peat properties (most are taken from other sources: references provided therein). 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
Impact This data has been used in our publication in Geoscientific Model Development (Chadburn et al 2022). It has also been used by a PhD student as a basis for her study on tropical peatlands. 
URL https://zenodo.org/record/5818180
 
Title Dataset of snow and soil temperature from Northern Norway 
Description Two years of data on snow depths and temperatures have been generated for this research site including installation and subsequent collection of equipment, and processing of data. More years will follow and data will be published/made available later in the project. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? No  
Impact This is now being used by Noah Smith (my PhD student) to improve the JULES model, which contributes towards his PhD. Improvements to JULES will also benefit the wider research community in the UK and internationally. 
 
Title New JULES model version with microbial methane scheme 
Description This adds a representation of methanogenic microorganisms into the Joint UK Land Environment Simulator (JULES), this improves the simulation of methane emissions from the JULES model. This is now available in the latest release of JULES (version 5.9, released 2021) for all JULES users. 
Type Of Material Computer model/algorithm 
Year Produced 2020 
Provided To Others? No  
Impact This new methane scheme in JULES will be used in the JULES contribution to the latest round of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP, https://www.isimip.org/), which is being prepared at the Met Office. 
URL https://code.metoffice.gov.uk/trac/jules/browser/main/trunk
 
Description ISIMIP peat sector 
Organisation Potsdam Institute for Climate Impact Research
Country Germany 
Sector Learned Society 
PI Contribution The Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) is coordinated by the Potsdam Institute for Climate Impact Research. I am part of a group who are organising a new 'peatland' sector within this project.
Collaborator Contribution Providing the whole framework of ISIMIP, protocols and driving datasets.
Impact Outputs not available yet.
Start Year 2020
 
Description TMOSAiC Permafrost Thaw Action Group 
Organisation Alfred-Wegener Institute for Polar and Marine Research
Department Geoscientific Department
Country Germany 
Sector Private 
PI Contribution Co-leading the Action Group. Organising a larger team of scientists to produce the outputs described below, as well as contributing to those outputs.
Collaborator Contribution Leading (AWI) and co-leading (Alaska) the Action Group. Organising a larger team of scientists to produce the outputs described below, as well as contributing to those outputs. App development and provision of data storage system.
Impact A protocol for measuring permafrost thaw and its drivers that can be used by non-experts and whose resulting data should be applicable for modelling. A paper published in Arctic Science describing the protocol and its scientific basis. In tandem with the protocol, an easy-to-use app for data entry that will allow all data collection by collaborators and citizen scientists to be assimilated into a data storage and analysis system. Data collected from a number of sites
Start Year 2019
 
Description TMOSAiC Permafrost Thaw Action Group 
Organisation University of Alaska Fairbanks
Country United States 
Sector Academic/University 
PI Contribution Co-leading the Action Group. Organising a larger team of scientists to produce the outputs described below, as well as contributing to those outputs.
Collaborator Contribution Leading (AWI) and co-leading (Alaska) the Action Group. Organising a larger team of scientists to produce the outputs described below, as well as contributing to those outputs. App development and provision of data storage system.
Impact A protocol for measuring permafrost thaw and its drivers that can be used by non-experts and whose resulting data should be applicable for modelling. A paper published in Arctic Science describing the protocol and its scientific basis. In tandem with the protocol, an easy-to-use app for data entry that will allow all data collection by collaborators and citizen scientists to be assimilated into a data storage and analysis system. Data collected from a number of sites
Start Year 2019
 
Description Testing a new type of snow sensor 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution Collection and installation of the snow sensor in Norway. Reading of the data from the sensor and comparison with snow data measured by alternative methods.
Collaborator Contribution Provision of the snow sensor (Imperial College) and the stand to mount it on (CEH), as well as expert advice.
Impact Data on snow depth has been produced that tests this type of sensor in a cold environment for the first time. This data matches well with data collected by an alternative method, which provides support for the validity of both measurement devices. I am also using the snow data in ongoing work related to my grant. We hope that this work should provide evidence that can be used in future grant applications but these have not happened yet.
Start Year 2019
 
Description Testing a new type of snow sensor 
Organisation UK Centre for Ecology & Hydrology
Country United Kingdom 
Sector Public 
PI Contribution Collection and installation of the snow sensor in Norway. Reading of the data from the sensor and comparison with snow data measured by alternative methods.
Collaborator Contribution Provision of the snow sensor (Imperial College) and the stand to mount it on (CEH), as well as expert advice.
Impact Data on snow depth has been produced that tests this type of sensor in a cold environment for the first time. This data matches well with data collected by an alternative method, which provides support for the validity of both measurement devices. I am also using the snow data in ongoing work related to my grant. We hope that this work should provide evidence that can be used in future grant applications but these have not happened yet.
Start Year 2019
 
Description 'Permafrost day' at Cryosphere Pavillion at the Conference of Parties in Madrid 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact I co-organised a day of presentations of the latest permafrost research in a 'side event' at the Conference of Parties. As part of that I presented my latest research. Around 40 people attended the talk, which included a mixture of policy makers, scientists and the public.
There were also a similar number of participants watching the live broadcast, and the youtube recording of the live broadcast of the part of the session with my presentation has 145 views. (url below)
The broadcast has been watched by school pupils in a school near Exeter who have included discussion of it in their written work.
Year(s) Of Engagement Activity 2019
URL https://www.youtube.com/watch?v=9rKod7QX5qk
 
Description Presentation and participation at peatland microbiology 'special interest group' workshops 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact I attended two workshops on a NERC funded series of workshops on peatlands and microbiology. I presented results from this project and I engaged in discussions with peatland management practitioners. A set of research priorities were identified.
Year(s) Of Engagement Activity 2019,2020
 
Description Presentation at Conference of Parties in Glasgow 2021 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I presented at "Permafrost day" in the Cryosphere Pavillion organised by the ICCI. Was told by people outside science that they had learned about the impact of permafrost on anthropogenic carbon budgets thanks to my presentations.
Year(s) Of Engagement Activity 2021
URL https://www.youtube.com/watch?v=sRvUyiYM0ko
 
Description Science blog 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I continued updating my research blog during the project, describing the project activities for a general audience. This has influenced undergraduate students who have applied for summer projects or for PhD projects with me (eg my current PhD student had been following the blog when he applied).
Year(s) Of Engagement Activity 2019,2020
URL http://sarahchadburn.com