TY - JOUR
T1 - Predicting the response of the Amazon rainforest to persistent drought conditions under current and future climates
T2 - A major challenge for global land surface models
AU - Joetzjer, E.
AU - Delire, C.
AU - Douville, H.
AU - Ciais, P.
AU - Decharme, B.
AU - Fisher, R.
AU - Christoffersen, B.
AU - Calvet, J. C.
AU - Da Costa, A. C.L.
AU - Ferreira, L. V.
AU - Meir, P.
N1 - Publisher Copyright:
© Author(s) 2014.
PY - 2014/12/10
Y1 - 2014/12/10
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84916605775&partnerID=8YFLogxK
U2 - 10.5194/gmd-7-2933-2014
DO - 10.5194/gmd-7-2933-2014
M3 - Article
SN - 1991-959X
VL - 7
SP - 2933
EP - 2950
JO - Geoscientific Model Development
JF - Geoscientific Model Development
IS - 6
ER -