[DLS] Wu Sun (Carnegie)

“Mapping the Breathing of the Biosphere Using Tracers in the Air” 

The terrestrial biosphere offers us a key climate service by taking up one-third of human-induced carbon emissions. Whether this terrestrial carbon sink will persist in a warmer, higher-carbon dioxide (CO₂) world is uncertain, as it hinges on whether photosynthesis outpaces respiration. To project coupled carbon–climate trajectories, we need to understand how photosynthesis and respiration respond to climate, particularly at scales relevant to setting climate goals. Yet, this effort has been challenging because surface flux observations are too sparse to inform biome-scale responses. Moreover, these observations track the balance between photosynthesis and respiration, but not each component.

I show how atmospheric observations of CO₂ and carbonyl sulfide, a tracer for photosynthesis, can shed new light on responses of photosynthesis and respiration to climate. Using tall-tower CO₂ observations, I determine carbon flux patterns and infer temperature responses of respiration for North American biomes. I also show how carbonyl sulfide enables us to track photosynthesis independently of respiration from leaf to biosphere scales. Combined, this pair of tracers can refine our understanding of carbon cycle processes and improve carbon–climate projections. Building on this body of work, I will sketch out a vision for future research to track the biosphere’s feedbacks to climate, especially in vulnerable biomes that may tip the carbon balance within this century.

[DLS] EAPS Department Lecture Series 

Weekly talks aimed to bring together the entire EAPS community, given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. Runs concurrently with class 12.S501. 

Contact: eapsinfo@mit.edu