Dr Anna Harper
Every year humans emit nearly 10 billion tonnes of CO2 into the atmosphere. Lucky for us, less than half of that remains in the atmosphere - the other half is split almost evenly between ocean and terrestrial storage. On the land, plants take in CO2 through photosynthesis, and this carbon can be stored for long periods in vegetation or soils. We call this the land carbon sink. The strength of the sink can vary dramatically from year to year, and it's unknown how long the land will continue to serve as a sink of anthropogenic carbon.
My research focuses on reducing uncertainty in the land carbon sink. An important question with climate change is how will terrestrial storage of CO2 be affected? If climate change reduces the CO2 stored on land, there will be a positive feedback as more CO2 will go into the air and cause further climate change. Therefore it's essential to get a better grasp on what will happen to vegetation with climate change.
I am now beginning an EPSRC Fellowship to investigate the potential for negative emissions of CO2 through bioenergy crops with carbon capture and storage. This is a possible mitigation strategy for keeping climate change below 2C warming since the Pre-Industrial period.
I am particularly interested in the Amazon rainforest, an amazing ecosystem which provides invaluable services to humanity - not least of which is the storage of CO2. Drought threatens this ecosystem. How the forest responds to droughts and the likelihood of future droughts will both play large roles in the future of the global carbon cycle and climate. Below is further description of some projects I am working on.
Plants "eat" CO2 to live, so to first order vegetation will benefit from growing atmospheric CO2 concentrations. In reality, there are several complicating factors which will control how much extra CO2 plants can assimilate: changes in weather and climate patterns, changes in nutrient availability, and human land use change and degradation. I'm involved in a project to better understand how plants will respond to rising CO2 using "FACE" (free-air enrichment of CO2) experiments. During these experiments, extra CO2 is pumped into a study area and the responses of the plants and soils are measured. My role is to use JULES to see which processes might be most important in the real world that are missing in earth system models. There is an exciting new FACE project at the University of Birmingham, BiFor FACE.
The global carbon budget:
Simulations by Andy Wiltshire (UK Met Office) and I using the JULES land surface model contributed to the 2013 global carbon budget, read the summary here: http://www.metoffice.gov.uk/research/news/gcb-2013
Recent Publications (please e-mail me if you would like a copy but do not have access to a journal)
AB Harper et al., Improved representation of plant functional types and physiology in the Joint UK Land Environment Simulator (JULES v4.2) using plant trait information. Geoscientific Model Development Discussions.
JM Osborne, FH Lambert, AB Haprer, M Groenendijk, S Sitch, CD Koven, B Poulter, TAM Pugh, BD Stocker, A Wiltshire, S Zaehle (2015), Reconciling precipitation with runoff: observed hydrological changes in mid-latitudes. Journal of Hydrometeorology.
P Good, AB Harper, A Meesters, E Robertson, R Betts (2015), Are strong fire-vegetation feedbacks needed to explain the spatial distribution of tropical tree cover? Accepted to Global Ecology and Biogeography.
A Anav, P Friedlingstein, C Beer, P Ciais, A Harper, C Jones, G Murray-Tortarolo, D Papale, NC Parazoo, P Peylin, S Piao, S Sitch, N Viovy, A Wiltshire, M Zhao (2015): Spatio-temporal patterns of terrestrial gross primary production: A Review. Review of Geophysics.
G Murray-Tortarolo, P Friendlingstein, S Sitch, VJ Jaramillo, F Murguia-Flores, A Anav, Y Liu, A Arneth, A Arvanitis, AB Harper, A Jain, E Kato, C Koven, B Poulter, BD Stocker, A Wiltshire, S Zaehle, N Zeng (2015): The carbon cycle in Mexico: past, present, and future of C stocks and fluxes. Biogeosciences Discussions.
NC Parazoo, E Barnes, J Worden, AB Harper, KW Bowman, C Frankenberg, S Wolf, M Litvak, TF Keenan (2015): Influence of ENSO and the NAO on terrestrial carbon uptake in the Texax-northern Mexico region. Global Biogeochemical Cycles.
Rowland, L., AB Harper, B. O. Christoffersen, D. R. Galbraith, H. M. A. Imbuzeiro, T. L. Powell, C. Doughty, N. M. Levine, Y. Malhi, S. R. Saleska, P. R. Moorcroft, P. Meir, and M. Williams, (2015) Modelling climate change responses in tropical forests: similar productivity estimates across five models, but different mechanisms and responses. Geoscientific Model Development.
AB Harper, IT Baker, AS Denning, DA Randall, D Dazlich, M Branson, (2014) Impact of evapotranspiration on dry season climate in the Amazon forest. Journal of Climate.
- Press release: http://www.exeter.ac.uk/news/featurednews/title_334187_en.html
IT Baker, AB Harper, HR Rocha, AS Denning, AC Araujo, LS Borma, HC Freitas, ML Goulden, AO Manzi, SD Miller, AD Nobre, N Restrepo-Coupe, SR Saleska, R Stockli, C Randow, SC Wofsy (2013), Surface ecophysiological behavior across vegetation and moisture gradients in tropical South America. Agricultural and Forest Meteorology.
TL Powell, DR Galbraith, BO Christoffersen, AB Harper, HMA Imbuzeiro, L Rowland, S Almeida, PM Brando, ACL da Costa, MH Costa, NM Levine, Y Malhi, SR Saleska, E Sotta, M Williams, P Meir, PR Moorcroft (2013), Confronting model predictions of carbon fluxes with measurements of Amazon forests subjected to experimental drought. New Phytologist.
AB Harper, AS Denning, IT Baker, MD Branson, L Prihodko, DA Randall (2010), Role of deep soil moisture in modulating climate in the Amazon forest. Geophysical Research Letters.