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The changing carbon cycle at Mauna Loa Observatory
Wolfgang Buermann1, Benjamin R Lintner, Charles D Koven
1Berkeley Atmospheric Sciences Center and Department of Geography, University of California, Berkeley, CA 94720, USA.
Summary
The seasonal carbon dioxide (CO2) cycle amplitude at Mauna Loa decreased due to North American droughts and changing air masses, impacting global carbon flux documentation. Recent rainfall suggests a recovery of the North American carbon sink.
Area of Science:
- Atmospheric Science
- Climate Science
- Ecology
Background:
- The amplitude of the seasonal carbon dioxide (CO2) cycle at Mauna Loa Observatory (MLO) has shown complex trends, increasing from the 1970s to the 1990s and decreasing thereafter, despite global warming.
- MLO's location influences its reception of Eurasian air masses in winter and North American air masses in summer, reflecting regional carbon cycle dynamics.
Purpose of the Study:
- To analyze the drivers behind the observed changes in the MLO CO2 seasonal cycle amplitude.
- To investigate the roles of North American and Eurasian carbon fluxes and atmospheric circulation in modulating the MLO CO2 record.
Main Methods:
- Analysis of CO2 seasonal cycle amplitude at Mauna Loa Observatory.
- Correlation of MLO data with atmospheric circulation patterns and land surface conditions (e.g., Normalized Difference Vegetation Index).
- Comparison of findings with historical data and established carbon cycle models.
Main Results:
- The increase in MLO CO2 amplitude from the 1970s to 1990s was linked to enhanced photosynthesis in North America and respiration in Eurasia.
- A subsequent decline in amplitude was attributed to reduced North American carbon sequestration during severe droughts (1998-2003) and altered atmospheric circulation.
- A sharp increase in MLO amplitude post-2004, coinciding with increased rainfall, indicated a recovery of the North American carbon sink.
Conclusions:
- Atmospheric CO2 measurements at remote sites are crucial for tracking land carbon flux changes.
- Droughts, exacerbated by global warming, significantly impact regional and global carbon cycles.
- Continued monitoring is essential for understanding the effects of climate change on terrestrial ecosystems and carbon sequestration.
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