From rain to radiance - Drivers of tropical carbon flux interannual variability shift with local climate

Tropical land carbon fluxes drive the inter-annual variability (IAV) of the atmospheric CO2 growth rate. However, what mechanistic processes and climate variables drive the IAV of tropical land carbon exchange remains debated. Here, we use a Bayesian framework that ingests a suite of satellite-based carbon and water observables to quantify the relative contributions of different climate variables to the tropical land carbon exchange IAV. We find the dominant climate drivers for carbon exchange depend on climate states. Radiation dominates the IAV of gross primary production (GPP) in wetter tropical forests, especially during La Niña and wet seasons, while VPD dominates GPPIAV in drier forests, with more pronounced influence during El Niño and dry seasons. Precipitation predominantly drives heterotrophic respiration IAV. Net ecosystem exchange IAV is more closely linked to ecosystem respiration than GPP. Our findings yield novel insights into the complex interplay among tropical climate gradients and IAV in climate states and carbon fluxes.