The carbon cycle response of the Amazon forest during the 2010 drought in dynamic global vegetation models
Anna B Harper1,2, Pierre Friedlingstein3, Stephen Sitch3, Peter Michael Cox4, Chris Jones2, Almut Arneth5, Athanasios Arvanitis6, Philippe Ciais7, Christian Frankenberg8, Atul K Jain9, Etsushi Kato10, Sam Levis11, Nick Parazoo12, Benjamin Poulter13, Benjamin David Stocker14, Andy Wiltshire2 and Soenke Zaehle15, (1)University of Georgia, Department of Geography, Athens, GA, United States, (2)Met Office Hadley Centre, Exeter, United Kingdom, (3)University of Exeter, Faculty of Environment, Science and Economy, Exeter, United Kingdom, (4)University of Exeter, Exeter, United Kingdom, (5)Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany, (6)Karlsruhe Institute of Technology, Karlsruhe, Germany, (7)LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette, France, (8)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States, (9)University of Illinois at Urbana Champaign, Department of Climate, Meteorology and Atmospheric Sciences, Urbana, United States, (10)NIES National Institute of Environmental Studies, Ibaraki, Japan, (11)National Center for Atmospheric Research, Boulder, United States, (12)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (13)Spark Climate Solutions, Greenbelt, United States, (14)Imperial College London, London, SW7, United Kingdom, (15)Max Planck Institute for Biogeochemistry, Biogeochemical Signals, Jena, Germany
Abstract:
Understanding the mechanisms behind the carbon cycle response to extreme events is essential for predicting future behaviour of tropical forests. In this study, we focus on the modelled response during the 2010 drought in the Amazon forest using a suite of dynamic global vegetation models. The potential impacts of drought on the carbon cycle include increased mortality, reduced productivity, and changes to heterotrophic and autotrophic respiration rates. In addition, the 2010 drought was accompanied by substantial biomass burning which also emitted CO
2 to the atmosphere. Many of these fires were from human ignitions related to deforestation, which can be particularly difficult for models to represent.
During the 2000’s, the models all showed that the forests of the Amazon basin were a net sink of CO2, with an average net biome productivity, or NBP, of 0.20±0.19 PgC/yr. This is within the range of bottom-up and top-down estimates of NBP in undisturbed forests (0.39+/-0.26 PgC/yr and 0.25+/-0.14 PgC, respectively) [Phillips et al. 2009, Gloor et al. 2012, Gatti et al. 2014]. This sink was reduced during the 2010 drought but the models tend to underestimate the severity of the reduction. The model average NBP during 2010 was -0.12 PgC, compared to -0.48±0.18 PgC from an observational study [Gatti et al. 2014]. In particular, the models simulated positive NBP during the dry season of 2010, indicating a carbon sink even during the peak drought months. This result is in direct contrast to recent estimates of seasonal terrestrial fluxes during 2010 based on atmospheric measurements [Gatti et al. 2014]. We investigate the roles of fire CO2 emissions, GPP sensitivity to drought, and uncertainty in driving data in the modelled responses, utilizing the GOSAT retrievals of chlorophyll fluorescence and the Global Fire Emissions Dataset. Based on this analysis we will identify priorities for continued model development of DGVMs in tropical forests.
