Terrestrial methane cycling during Paleogene greenhouse climates

Lead Research Organisation: Royal Holloway, University of London
Department Name: Earth Sciences

Abstract

Human activity has led to an increase in pCO2 and methane levels from pre-industrial times to today. While the former increase is primarily due to fossil fuel burning, the increase in methane concentrations is more complex, reflecting not only direct human activity but also feedback mechanisms in the climate system related to temperature and hydrology-induced changes in methane emissions. To unravel these complex relationships, scientists are increasingly interrogating ancient climate systems. Similarly, one of the major challenges in palaeoclimate research is understanding the role of methane biogeochemistry in governing the climate of ice-free, high-pCO2 greenhouse worlds, such as during the early Paleogene (around 50Ma). The lack of proxies for methane concentrations is problematic, as methane emissions from wetlands are governed by precipitation and temperature, such that they could act as important positive or negative feedbacks on climate. In fact, the only estimates for past methane levels (pCH4) arise from our climate-biogeochemistry simulations wherein GCMs have driven the Sheffield dynamic vegetation model, from which methane fluxes have been derived. These suggest that Paleogene pCH4 could have been almost 6x modern pre-industrial levels, and such values would have had a radiative forcing effect nearly equivalent to a doubling of pCO2, an impact that could have been particularly dramatic during time intervals when CO2 levels were already much higher than today's. Thus, an improved understanding of Paleogene pCH4 is crucial to understanding both how biogeochemical processes operate on a warmer Earth and understanding the climate of this important interval in Earth history.

We propose to improve, expand and interrogate those model results using improved soil biogeochemistry algorithms, conducting model sensitivity experiments and comparing our results to proxy records for methane cycling in ancient wetlands. The former will provide a better, process-orientated understanding of biogenic trace gas emissions, particularly the emissions of CH4, NOx and N2O. The sensitivity experiments will focus on varying pCO2 levels and manipulation of atmospheric parameters that dictate cloud formation; together, these experiments will constrain the uncertainty in our trace greenhouse gas estimates. To qualitatively test these models, we will quantify lipid biomarkers and determine their carbon isotopic compositions to estimate the size of past methanogenic and methanotrophic populations, and compare them to modern mires and Holocene peat. The final component of our project will be the determination of how these elevated methane (and other trace gas) concentrations served as a positive feedback on global warming.

In combination our work will test the hypothesis that elevated pCO2, continental temperatures and precipitation during the Eocene greenhouse caused increased wetland GHG emissions and atmospheric concentrations with a significant feedback on climate, missing from most modelling studies to date. This work is crucial to our understanding of greenhouse climates but such an integrated approach is not being conducted anywhere else in the world; here, it is being led by international experts in organic geochemistry, climate, vegetation and atmospheric modelling, and palaeobotany and coal petrology. It will represent a major step forward in our understanding of ancient biogeochemical cycles as well as their potential response to future global warming.

Planned Impact

Our proposal is of wide and direct relevance to the Earth Sciences academic community and associated stakeholders. It explicitly addresses two strategic themes of the new NERC strategy for 2007-2012: Earth System Science and Biodiversity. In particular, our research meets three of the six key outcomes identified in the overarching 'Earth system science' theme, as NERC seeks to provide "knowledge of the impact of potential mitigation and adaptation strategies to forthcoming climate change", "understand tipping points and rates of change", and aims to provide "better assessment of the risk of changes in the Earth system to inform policy decisions". The results of this proposal help the UK meet the strategy challenges to "provide forewarning of abrupt changes in the Earth System", to "improve knowledge of the interaction between the evolution of life and the Earth", and to "understand the forces and feedbacks that drive the Earth System". As such, prompt and high profile delivery of our results to our scientific peers is a key component of our Impact strategy, and we have requested funds for conference attendance by the PI, CoIs and PDRAs. We have a very strong track record in conference attendance (including invited keynote presentations) and rapid, high profile publication of our work; that good practice will be continued as part of the proposed work.

Of course, our conclusions will also be of wide interest to the public, policy makers, climate-orientated NGOs and other NERC stakeholders; we, as a society, will benefit from this research because it furthers our understanding of climate change and informs our predictions for future change. As such, we have an ambitious impact programme built around two main (non-academic) themes:

1. Public engagement. The University of Bristol is a national leader in public engagement: Bristol, along with the University of the West of England, is the coordinator of the national engagement beacons; we had the first Professor of Public Engagement (K Sykes); and our two Centres of Excellence in Chemistry and Anatomy are world leading in terms of the quantity and quality of outreach activity. The PI and our Co-Is have been particularly active in this capacity, including serving on the organising committee for the Bristol Festival of Nature, hosting BBC series, giving >100 talks to fellow scientists and the wider public and writing books marketed to the general public (The Emerald Planet: How Plants Changed Earth's History by DJB). Funds to support our Impact Plan will allow us to exploit the best practices developed elsewhere, allowing us to: embed a methane component in the Bristol ChemLabS lecture series (>100 lectures to ca 30,000 people per year); develop a website, complete with interactive tools; and have a prominent display at the Bristol Festival of Nature hosted by ourselves but also Sixth Form students who will have done summer internships in our labs.

2. Stakeholder engagement: We have hosted MPs in the past, and Pancost and Singarayer have numerous connections with the Bristol City Council via our involvement in the University of Bristol centenary fund and the Bristol Festival of Nature. Also via the Festival of Nature, we have excellent connections with the Environment Agency and charitable trusts devoted to wetland awareness and conservation. We will use these connections to host events where our research is explained to and discussed with a range of stakeholders. It is our intention to make our political leaders more aware of the sensitivity of wetlands to climate change - and therefore, the need to better understand these environments. Of course, this will also be an ideal mechanism to update policy makers with the most up-to-date research on this particular 'tipping point' in the Earth System, a particularly important goal of the NERC.

Publications

10 25 50
 
Description From Robson et al (2015)
Charred particles recovered from lignites were mostly woody and lacked the diversity of plant parts (such as flowers, fern leaf stalks) than can be found in fossil charcoal assemblages from other time intervals (e.g. Cretaceous).

Charcoal percentages from in situ pillars and crushed samples representing the same part of a lignite seam are typically similar, suggesting that either method can be used for study of 'homogeneous' lignites.

Charcoal relative abundance was not linked to conditions (e.g. wetness or dryness of peat surface) of peat-formation.

The early Paleogene at Schoeningen, Germany, experienced higher wildfire activity than modern climates.

Wildfire activity fell to modern levels in the middle of the Early Eocene, earlier than previous research suggested.

Increased wildfire occurred within the interval including the Early Eocene climatic optimum.

From Inglis et al (2015)
Inertinite percentages can vary considerably within a single lignite seam. This suggests that the sampling interval should be carefully considered and that an average inertinite percentage for an entire seam is the most appropriate indicator of overall wildfire activity in the past.

From the Eocene coals database
For some areas of the world there are no records of Early Eocene lignites. In other areas Eocene lignites exist but are poorly dated or not available in outcrop for study. Improved dating of lignites or new boreholes would both enable a more global Eocene coals (Eocene wetlands) database to be produced.

Unpublished so far
Charcoal in fluvial and marginal marine settings at Schoeningen, Germany, shows a similar distribution to that in lignites. However, the relative amount of charcoal in these settings is strongly influenced by transport and concentration effects so is a less reliable indicator of variation in wildfire activity than charcoal in peat-forming environments (i.e. lignites) which is very unlikely to have been transported
Exploitation Route Findings will be useful for palaeobiologists, palaeobotanists and palaeoclimatologists and fire scientists. They should be of interest for planners considering management of changes in fire activity in future warm climates.
Sectors Education,Environment

URL http://www.sciencedirect.com/science/article/pii/S0031018215003764
 
Title Early Paleogene coals database 
Description Early Paleogene coal sites gathered from extensive literature research and contact with specialists 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
Impact The database has been used as part of a map of Paleogene wetlands by our collaborators in Bristol researching methane release in the early Paleogene (lead institute part of grant award NE/J008656/1 to RHUL). The database is also part of a manuscript for publication the first draft of which has been sent out to all co-authors and their comments have been received by my supervisor. The database will also be part of my tied PhD studentship students thesis. 
 
Description Global Paleogene fire research French site 
Organisation University of Mons
Country Belgium 
Sector Academic/University 
PI Contribution Analysis of charcoal data at a site in France spanning the PETM (Paleocene Eocene thermal maximum) onset which is co-eval to the Cobham site in the UK and on which our French colleagues have been working for many years.
Collaborator Contribution Guidance in the field and assistance with collecting samples and ensuring their correct stratigraphic context
Impact None yet. Draft manuscript for publication has been circulated to all co-authors and their comments received
Start Year 2009
 
Description Global Paleogene fire research German site 
Organisation Senckenberg Research Institute and Nature Museum Senckenberganlage
Country Germany 
Sector Public 
PI Contribution Charcoal analysis through the Early Eocene of the Schöningen Mine in Germany, a site which these colleagues had been studying (sedimentology, palynology, palaeoclimate) for more than two decades.
Collaborator Contribution Organisation of permission to enter the mine based on their existing good relations with miners and mining company; logistical help with field organisation; guidance in the mine especially for stratigraphic context; vital help with field sampling and with carrying heavy field samples and packing same for transport to Royal Holloway. Archiving of duplicate sample set in the Senckenberg Museum.
Impact http://dx.doi.org/10.1016/j.palaeo.2015.07.016 http://dx.doi.org/10.1016/j.palaeo.2015.08.001 Another publication in progress, draft manuscript circulated to all co-authors and their comments received
Start Year 2008
 
Description Global Paleogene fire research German site 
Organisation Technical University of Darmstadt
Country Germany 
Sector Academic/University 
PI Contribution Charcoal analysis through the Early Eocene of the Schöningen Mine in Germany, a site which these colleagues had been studying (sedimentology, palynology, palaeoclimate) for more than two decades.
Collaborator Contribution Organisation of permission to enter the mine based on their existing good relations with miners and mining company; logistical help with field organisation; guidance in the mine especially for stratigraphic context; vital help with field sampling and with carrying heavy field samples and packing same for transport to Royal Holloway. Archiving of duplicate sample set in the Senckenberg Museum.
Impact http://dx.doi.org/10.1016/j.palaeo.2015.07.016 http://dx.doi.org/10.1016/j.palaeo.2015.08.001 Another publication in progress, draft manuscript circulated to all co-authors and their comments received
Start Year 2008
 
Description Global Paleogene fire research German site 
Organisation University of Göttingen
Country Germany 
Sector Academic/University 
PI Contribution Charcoal analysis through the Early Eocene of the Schöningen Mine in Germany, a site which these colleagues had been studying (sedimentology, palynology, palaeoclimate) for more than two decades.
Collaborator Contribution Organisation of permission to enter the mine based on their existing good relations with miners and mining company; logistical help with field organisation; guidance in the mine especially for stratigraphic context; vital help with field sampling and with carrying heavy field samples and packing same for transport to Royal Holloway. Archiving of duplicate sample set in the Senckenberg Museum.
Impact http://dx.doi.org/10.1016/j.palaeo.2015.07.016 http://dx.doi.org/10.1016/j.palaeo.2015.08.001 Another publication in progress, draft manuscript circulated to all co-authors and their comments received
Start Year 2008
 
Description Global Paleogene fire research New Zealand site 
Organisation GNS Science
Country New Zealand 
Sector Public 
PI Contribution Analysis of New Zealand Late Cretaceous and Paleogene lignite samples for charcoal - first time these analyses have been done for New Zealand. Follow up from attendance by Collinson at conference and field trip in New Zealand in 2009 when a few trial samples were collected.
Collaborator Contribution Field collection (following our protocols) and mailing of samples to us.
Impact None yet - Draft of intended publication has been shared with all co-authors and their comments received. Multidisciplinary - palynology, isotope geochemistry, sedimentology, charcoal analysis
Start Year 2014
 
Description Global Paleogene fire research Venezuala site 
Organisation Smithsonian Institution
Department Smithsonian Tropical Research Institute
Country Panama 
Sector Public 
PI Contribution Analysis of charcoal in Late Paleocene and Early Eocene samples from Venezuala a site from which the Paleocene Eocene thermal maximum has been reported along with data on vegetation change based on palynology
Collaborator Contribution Provision of samples from sample suite already collected, mailing of samples to us.
Impact None yet. Draft manuscript for publication has been shared with co-authors and their comments have been received.
Start Year 2013
 
Description European Palaeobotany and Palynology Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Oral presentation on implications of fossil plant material (in this case charcoal from Schoeningen) for understanding ancient wildfire
Year(s) Of Engagement Activity 2014
URL http://www.socgeol.it/206/1517/news/9th-european-palaeobotany-and-palynology-conference.html
 
Description Linnean Society Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Introduced my research to other researchers and incited interesting discussion.
Year(s) Of Engagement Activity 2013
 
Description School visit 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Talk inspired further interest in science

n/a
Year(s) Of Engagement Activity 2013
 
Description Undergraduate project Schöningen charcoal in siliciclastics 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Undergraduate student final year independent research project (one whole course unit) - charcoal in fluvial and marginal marine siliciclastic sediments at Schöningen - comparison with the record from lignites (former peat-forming environments) at the same site. Student presented a 15 minute seminar to peers and staff and will produce a research report (8000 words) due end of March 2016.
The options in next question do not include - skills training for student - which is a key outcome.
Year(s) Of Engagement Activity 2015,2016
 
Description Workshop on petrology 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Shared ideas and discussed interpretations of coal macerals. Requests for further participation based on Schoeningen fungal material
Year(s) Of Engagement Activity 2015