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Soil moisture-atmosphere feedback dominates land carbon uptake variability.
Vincent Humphrey1, Alexis Berg2, Philippe Ciais3
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA. vincent.humphrey@caltech.edu.
Nature
|April 1, 2021
Summary
Soil moisture variability drives 90% of global land carbon uptake changes annually, primarily impacting photosynthesis. Soil moisture-atmosphere feedbacks amplify climate effects, influencing the terrestrial carbon cycle and atmospheric carbon dioxide levels.
Area of Science:
- Earth System Science
- Ecology
- Climate Science
Background:
- Terrestrial ecosystems play a crucial role in regulating atmospheric carbon dioxide (CO2) concentrations through their year-to-year carbon uptake variations.
- The precise influence of temperature and water availability on these global-scale carbon uptake fluctuations remains an area of uncertainty.
Purpose of the Study:
- To quantify the contributions of soil moisture and temperature to inter-annual variability in global land carbon uptake.
- To investigate the mechanisms, including feedback loops, through which soil moisture influences land carbon uptake.
Main Methods:
- Utilized factorial climate model simulations to disentangle the effects of climate variables on land carbon uptake.
- Analyzed the indirect impacts of soil moisture via soil moisture-atmosphere feedbacks on temperature and humidity.
Main Results:
- Soil moisture variability accounts for 90% of the inter-annual variability in global land carbon uptake, predominantly by affecting photosynthesis.
- Ecosystem responses are largely indirect, mediated by soil moisture-atmosphere feedbacks that amplify climate anomalies and soil water stress.
- Modelled land carbon uptake variability is primarily driven by temperature and vapor pressure deficit, both controlled by soil moisture.
Conclusions:
- Soil moisture is the dominant factor controlling global land carbon uptake variability.
- Accounting for soil moisture-atmosphere feedback mechanisms is essential for accurately predicting the carbon cycle's response to climate change.
- Findings underscore the importance of soil moisture dynamics in both global carbon cycle research and local drought impact studies.
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