Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 7, 2933-2950, 2014
https://doi.org/10.5194/gmd-7-2933-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Development and technical paper
10 Dec 2014
Predicting the response of the Amazon rainforest to persistent drought conditions under current and future climates: a major challenge for global land surface models
E. Joetzjer1, C. Delire1, H. Douville1, P. Ciais2, B. Decharme1, R. Fisher3, B. Christoffersen4, J. C. Calvet1, A. C. L. da Costa5, L. V. Ferreira6, and P. Meir7 1CNRM-GAME UMR3589, Groupe d'étude de l'atmosphère météorologique, Toulouse, France
2LSCE Laboratory of Climate Sciences and the Environment, Gif-sur-Yvette, France
3NCAR National Center for Atmospheric Research, Boulder, Colorado, USA
4School of GeoSciences, University of Edinburgh, Edinburgh, UK
5Universidade Federal de Para, Belem, Para, Brasil
6Museu Paraense Emilio Goeldi, Belem, Para, Brasil
7Australian National University, Canberra, Australia
Abstract. While a majority of global climate models project drier and longer dry seasons over the Amazon under higher CO2 levels, large uncertainties surround the response of vegetation to persistent droughts in both present-day and future climates. We propose a detailed evaluation of the ability of the ISBACC (Interaction Soil–Biosphere–Atmosphere Carbon Cycle) land surface model to capture drought effects on both water and carbon budgets, comparing fluxes and stocks at two recent throughfall exclusion (TFE) experiments performed in the Amazon. We also explore the model sensitivity to different water stress functions (WSFs) and to an idealized increase in CO2 concentration and/or temperature. In spite of a reasonable soil moisture simulation, ISBACC struggles to correctly simulate the vegetation response to TFE whose amplitude and timing is highly sensitive to the WSF. Under higher CO2 concentrations, the increased water-use efficiency (WUE) mitigates the sensitivity of ISBACC to drought. While one of the proposed WSF formulations improves the response of most ISBACC fluxes, except respiration, a parameterization of drought-induced tree mortality is missing for an accurate estimate of the vegetation response. Also, a better mechanistic understanding of the forest responses to drought under a warmer climate and higher CO2 concentration is clearly needed.

Citation: Joetzjer, E., Delire, C., Douville, H., Ciais, P., Decharme, B., Fisher, R., Christoffersen, B., Calvet, J. C., da Costa, A. C. L., Ferreira, L. V., and Meir, P.: Predicting the response of the Amazon rainforest to persistent drought conditions under current and future climates: a major challenge for global land surface models, Geosci. Model Dev., 7, 2933-2950, https://doi.org/10.5194/gmd-7-2933-2014, 2014.
Publications Copernicus
Download
Share