Impact of the 2015/2016 El Niño on the terrestrial carbon cycle constrained by bottom-up and top-down approaches

It is also a necessary step to build confidence in terrestrial ecosystems models' response to the warming and drying stresses expected in the future over many continents, and particularly in the tropics. Here we present an in-depth analysis of the response of the terrestrial carbon cycle to the 2015/2016 El Nino that imposed extreme warming and dry conditions in the tropics and other sensitive regions.

First, we provide a synthesis of the spatiotemporal evolution of anomalies in net land-atmosphere CO2 fluxes estimated by two in situ measurements based on atmospheric inversions and 16 land-surface models (LSMs) from TRENDYv6. Simulated changes in ecosystem productivity, decomposition rates and fire emissions are also investigated. Inversions and LSMs generally agree on the decrease and subsequent recovery of the land sink in response to the onset, peak and demise of El Nino conditions and point to the decreased strength of the land carbon sink: by 0.4-0.7 PgC yr(-1) (inversions) and by 1.0 PgC yr(-1) (LSMs) during 2015/2016.