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Climate Impacts on Net Carbon Sinks

Ten-day backtrajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) run with Global Data Assimilation System (GDAS) meteorology. Lines show the pathways of 100 air particles for ten days prior to when the air was sampled for CO2 measurements at 1713 m altitude above Tabatinga in the Amazonas state of Brazil during the wet season (February 17, 2010). Such "backtrajectories" can reveal where atmospheric CO2 signals originate; in this case, the airmass entered the continent from the northeast and likely picked up signals of photosynthesis, respiration and biomass burning as it passed over the Amazon before arriving in Amazonas.

 

 

Caroline Alden investigates the impacts of drought and temperature extremes on carbon cycling using atmospheric observations of carbon dioxide (CO2) and other trace gases.

Knowledge of how the land biosphere carbon cycle responds to climate and weather variability is key for prediction of future stability of carbon stocks in the face of climate change and extreme weather events.

Net land biosphere sinks and sources of CO2 represent the sum of a delicate balance of gross input to the biosphere via photosynthetic uptake and gross output from the biosphere through respiration and biomass burning. While gross inputs and outputs are difficult to measure over large areas, atmospheric concentrations of CO2 represent an integrated signal of net sink/source activity at climatically relevant scales.

Net surface fluxes of CO2 can be calculated using observations of atmospheric CO2 in conjunction with atmospheric transport models. Further, we combine knowledge of CO2 fluxes with observations of other trace gases, such as carbon monoxide (CO), methane (CH4) and the stable carbon isotope δ13C of CO2, to seek insights into the mechanistic responses of the carbon cycle to such forcings as drought and temperature extremes.

The Amazon Basin is home to one of the world’s most climatically important stocks of carbon, with some 100 billion tons of carbon stored as biomass (the equivalent of 10 years of fossil fuel emissions at 2014 rates of human combustion). Light aircraft have regularly sampled atmospheric CO2 at key locations across the Brazilian Amazon since 2010. Inverse modeling efforts are now yielding new insights into the sensitivity and coherence of Amazonian response to such climate extremes as the 2010 Amazon drought.