Abrupt seasonal transitions in land carbon uptake in 2015
Chao Yue1, Philippe Ciais1, Ana Bastos1, Frederic Chevallier1, Yi Yin1, and Christian Rödenbeck21Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, UMR8212, Gif-sur-Yvette, France 2Max Planck Institute for Biogeochemistry, Jena, Germany
Received: 23 Dec 2016 – Accepted for review: 11 Jan 2017 – Discussion started: 12 Jan 2017
Abstract. The year 2015 saw a record atmospheric CO2 growth rate associated with a weaker than usual land carbon sink. Paradoxically, it was also the greenest year since 2000 according to satellite observations of vegetation greenness. To reconcile these two seemingly paradoxical observations, we examined the patterns of CO2 fluxes using two atmospheric inversions. Inversion results indicate that the year 2015 had a higher than usual northern land carbon uptake in spring and summer, consistent with the greening anomaly. This higher uptake was however followed by a larger source of CO2 in autumn, suggesting a coupling between growing season uptake and late season release of CO2. For the tropics and Southern Hemisphere, a strong and abrupt transition toward a large carbon source for the last trimester of 2015 is discovered, concomitant with the El Niño development. This abrupt transition of terrestrial tropical CO2 fluxes between two consecutive seasons is the largest ever found in the inversion records.
Yue, C., Ciais, P., Bastos, A., Chevallier, F., Yin, Y., and Rödenbeck, C.: Abrupt seasonal transitions in land carbon uptake in 2015, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1167, in review, 2017.