Large influence of soil moisture on the terrestrial carbon cycle
Abstract
The terrestrial biosphere is estimated to absorb 25-30% of anthropogenic CO2 emissions, yet its uptake rate is the most uncertain CO2 flux, leading to large uncertainties in climate projections1,2.Using model runs from the Global Land-Atmosphere Coupling Experiment-Coupled Model Intercomparison Project phase 5 (GLACE-CMIP5)3 experiments, we show that soil moisture variability and gradual moisture regime shifts induce large CO2 sources, on the order of the land carbon sink itself, due to the nonlinear response of net ecosystem exchange to moisture availability and the associated land-atmosphere feedbacks. In other words, losses in net CO2 flux due to negative soil moisture anomalies are not compensated by similar but opposite wet anomalies. While simulated soil moisture quantitatively differs between models, models show a robust qualitative agreement on its strong effect on the ability of the biosphere to act as a carbon sink that is also confirmed by observations. Our results highlight the necessity of implementing improved, mechanistic representations of vegetation response to water stress and land-atmosphere coupling in Earth System Models, to improve our understanding of terrestrial carbon cycling, and better predict future climate.
1. Le Quéré, C. et al. Global Carbon Budget 2017. Earth Syst. Sci. Data 10, 405-448 (2018). 2. Ballantyne, A. P. et al. Audit of the global carbon budget: Estimate errors and their impact on uptake uncertainty. Biogeosciences 12, 2565-2584 (2015). 3. Seneviratne, S. I. et al. Impact of soil moisture-climate feedbacks on CMIP5 projections: First results from the GLACE-CMIP5 experiment. Geophys. Res. Lett. 40, 5212-5217 (2013).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B51G2012G
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0429 Climate dynamics;
- BIOGEOSCIENCESDE: 0434 Data sets;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES