What drives spatio-temporal variability of Africa's carbon fluxes and their connection to climate oscillations?

Terrestrial process models and atmospheric inversions attribute a large fraction of global interannual variability in net ecosystem carbon dioxide exchange to tropical lands. Africa, one of the least well-understood components of the global picture, reportedly contributes as much as one third of the year-to-year variation in global net carbon dioxide source/sink dynamics. Surprisingly small interannual variability of African fire emissions means photosynthesis and respiration can be expected to play a particularly important role in governing the continent's interannual variability of net ecosystem exchange. In this presentation, we report results from a biophysical model used to study what drives spatio-temporal patterns of photosynthesis and respiration in the various eco- climatic settings across the African continent, providing in-depth analysis of continental-scale patterns and focusing more specifically on what causes their year to year variation. Hydrologic fluctuations are the most important drive of interannual variability in photosynthesis since water deficit is prevalent and interannual variability of rainfall is high. While hydrologic fluctuations are often erratic, rainfall across much of Africa resonates with the El Nino Southern Oscillation and the Indian Ocean Dipole and this drives sizeable anomalies of the gross fluxes with substantial temporal correlation. In addition, we use flux tower observations to study where models are likely to suffer deficiencies associated with complicated biologically-regulated lags triggered by discrete wetting events.