Changing Land-Atmosphere Feedbacks in Tropical African Wetlands

Lead Research Organisation: University of Oxford
Department Name: Geography - SoGE

Abstract

The primary aim of the proposed research is to quantify the feedbacks between tropical African wetlands and climate. We will do this by implementing a dynamic wetland inundation scheme in an Earth system model, and test this model against soil moisture, cloud cover and methane (CH4) concentration data obtained through remote Earth observation. Our research will address the following key questions: How does the presence of tropical wetlands affect rainfall at the regional scale? Are wetland emissions of CH4 strongly dependent on seasonal and inter-annual hydrological variability? How will wetland seasonality and associated emissions of CH4 alter under environmental and climate change scenarios? The research proposed here will build on recent developments in land-surface modelling and Earth observation to incorporate detailed hydrological understanding of wetland function into climate models. We will combine novel satellite Earth observations, field measurements, and a new dynamical representation of wetland inundation to add greatly to our understanding of the importance of wetlands in the Earth system under scenarios of environmental change. Wetlands interact with the climate system in two ways. First, they govern the fluxes of heat and water at the land-surface, which can feed back on rainfall at the local and regional scales. Second, wetlands form a key link between the hydrological and carbon cycles, via anoxic degradation of organic matter to release CH4. It is estimated that wetland CH4 emissions represent 20-40% of the global CH4 budget making wetlands the largest single natural source of atmospheric CH4. Both CH4 and hydrological feedbacks are expected to be most active in the tropics, yet it is here that CH4 fluxes are least well quantified. These concerns are amplified in the context of climate change: warming resulting from a doubling of atmospheric CO2 concentrations will likely lead to a 78% increase in wetland emissions of CH4, most of which will come from tropical regions. Moreover, recent rapid increases in global CH4 concentrations have recently been attributed to natural variations in the extent of flooding in tropical wetlands. The lack of robust information on the ways in which tropical wetlands modulate fluxes of heat, water and trace gases to the atmosphere currently hampers progress in predicting the effects of global environmental change. We urgently need a better understanding of how wetlands function in the Earth system.

Publications

10 25 50
publication icon
Dadson S (2013) Water security, global change and land-atmosphere feedbacks. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

publication icon
Hall JW (2014) Water Security. Coping with the curse of freshwater variability. in Science (New York, N.Y.)

publication icon
Lewis H (2018) The UKC2 regional coupled environmental prediction system in Geoscientific Model Development

publication icon
Marthews T (2014) A high-resolution global dataset of topographic index values for use in large-scale hydrological modelling in Hydrology and Earth System Sciences Discussions

publication icon
Marthews T (2015) The 2014 Drought in the Horn of Africa: Attribution of Meteorological Drivers in Bulletin of the American Meteorological Society

Related Projects

Project Reference Relationship Related To Start End Award Value
NE/I01277X/1 26/04/2011 01/01/2012 £411,952
NE/I01277X/2 Transfer NE/I01277X/1 01/01/2012 30/04/2015 £391,845
 
Description 1. A model to calculate inland flooding at large-scales for use in climate modelling applications
2. Supporting datasets for use with the Met Office Hadley Centre Unified Model system
3. Understanding of the effects of surface-water inundation on land-atmosphere feedbacks
4. Use of Earth observation data to constrain methane cycle in tropical African wetlands
Exploitation Route Results and outputs are currently being used to support follow-on studies funded by NERC (FCFA) and DfID (IWSP).
Sectors Environment

URL http://www.geog.ox.ac.uk/research/landscape/projects/africanwetlands/
 
Description The findings of this work have been used to improve UK land-surface modelling capability through the enhancement of the Met Office Unified Model and JULES modelling system. We have also initiated several collaborative activities with researchers in Africa which have attracted follow-on funds via NERC (FCFA) and DfID IWSP (REACH).
First Year Of Impact 2014
Sector Environment
Impact Types Economic,Policy & public services

 
Description Leverhulme
Amount £20,000 (GBP)
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2015 
End 09/2018
 
Description REACH
Amount £15,000,000 (GBP)
Organisation Government of the UK 
Department Department for International Development (DfID)
Sector Public
Country United Kingdom
Start 09/2015 
End 09/2022
 
Description UKSA IPP
Amount £2,000,000 (GBP)
Organisation UK Space Agency 
Sector Public
Country United Kingdom
Start 03/2016 
End 03/2019
 
Title RFM in JULES 
Description River routing model (RFM) for use in Joint UK Land Environment Simulator (JULES) developed in collaboration with UK Met Office 
Type Of Material Computer model/algorithm 
Year Produced 2015 
Provided To Others? Yes  
Impact Contributes to UK Environmental Prediction capability 
 
Title Topographic Index global layer 
Description Here we present new, high-resolution parameter maps of the topographic index for all ice-free land pixels calculated from hydrologically-conditioned HydroSHEDS data using the GA2 algorithm ('GRIDATB 2'). At 15 arc-sec resolution, these layers are four times finer than the resolution of the previously best-available topographic index layers, the Compound Topographic Index of HYDRO1k (CTI). 
Type Of Material Database/Collection of data 
Year Produced 2014 
Provided To Others? Yes  
Impact Increasing the resolution at which global hydrological simulations are carried out will have many benefits including the more realistic representation of processes currently at subgrid resolution and, ultimately, better weather and inundation prediction. Methane production in wetlands, for example, is critically dependent on the level of the water table, models of which are in turn dependent on accurate representation of the topography, therefore higher resolution simulations involving improved topographic index values should of necessity improve the representation of wetland fluxes of heat, water and trace gases to the atmosphere and overall estimates of methane release. Data have been provided to: The Gordon & Betty Moore Foundation Andes-Amazon Project (coordinated by Prof. Moorcroft, Harvard Univ.) The Joint Research Centre (JRC), Ispra, Italy The Department of Life Sciences, Imperial College London Two separate researchers at the Max Planck Institute for Biogeochemistry (BGC-Jena) The Norwegian Forest and Landscape Institute (Skog og Landskap), Ås, Norway The BRIDGE Project, University of Bristol and The Water Resources & Coastal Engineering Laboratory, Technical University of Crete (TUC) 
URL http://eidchub.ceh.ac.uk/metadata/ce391488-1b3c-4f82-9289-4beb8b8aa7da
 
Description Airbus / UKSA 
Organisation Airbus Group
Department Airbus Defence & Space
Country United States 
Sector Private 
PI Contribution Collaboration with UKSA grant
Collaborator Contribution Collaboration with UKSA grant
Impact UKSA Grant
Start Year 2016
 
Description Met Office 
Organisation Meteorological Office UK
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaborative work to implement river routing scheme in Met Office Unified Model
Collaborator Contribution Collaborative work to implement river routing scheme in Met Office Unified Model
Impact This work is ongoing and will result in the capability to predict river flows in the Met Office Unified Model
Start Year 2012
 
Description NASA Jet Propulsion Lab 
Organisation National Aeronautics and Space Administration (NASA)
Department Jet Propulsion Laboratory
Country United States 
Sector Public 
PI Contribution *ºPaltan, H., Waliser, D., Lim, W. H., Guan, B., Yamazaki, D., Pant, R., & Dadson, S., 2017. Global floods and water availability driven by atmospheric rivers. Geophysical Research Letters, 44. https://doi.org/10.1002/2017GL074882
Collaborator Contribution This paper arose from an invited secondment into NASA/Caltech's Jet Propulsion Laboratory in Pasadena, CA by one of my graduate students. It is the most globally-extensive evaluation of the role of atmospheric rivers in the hydrological cycle to date
Impact *ºPaltan, H., Waliser, D., Lim, W. H., Guan, B., Yamazaki, D., Pant, R., & Dadson, S., 2017. Global floods and water availability driven by atmospheric rivers. Geophysical Research Letters, 44. https://doi.org/10.1002/2017GL074882
Start Year 2015
 
Description Oxford Water Network 
Organisation University of Cape Town
Country South Africa 
Sector Academic/University 
PI Contribution We have participated in this initiative and it has resulted in two successful research proposals, one to EPSRC and another to NERC.
Start Year 2012
 
Description DFID-REACH Panellist: Water Security in Africa 
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 150 people from Ethiopia, Kenya, Bangladesh attended a conference of which this panel was a component
Year(s) Of Engagement Activity 2019
 
Description Geographical Association Annual Pilgrim Lecture (to sixth formers) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact ~100 students from the region attended and participated in a discussion afterwards. I also held a session to demystify Oxbridge applications afterwards which was well attended.
Year(s) Of Engagement Activity 2016
 
Description OECD Global Water Partnership 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact OECD Global Water Partnership Task Force on Water Security, Risk and Growth
Year(s) Of Engagement Activity 2016
 
Description REACH Conference DFID 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Chaired panel discussion on Future Climate for Africa at DFID-REACH conference on Improving Water Security for the Poor. Engagement with senior civil servants from DfID, ministers and other policymakers from Ethiopia, Kenya, Bangladesh.
Year(s) Of Engagement Activity 2015
URL http://www.reachwater.org