Unusual characteristics of the carbon cycle during the 2015−2016 El Niño

Kai Wang, Xuhui Wang, Shilong Piao, Frédéric Chevallier, Jiafu Mao, Xiaoying Shi, Chris Huntingford, Ana Bastos, Philippe Ciais, Hao Xu, Ralph F. Keeling, Stephen W. Pacala, Anping Chen

Research output: Contribution to journalArticlepeer-review

Abstract

The 2015−2016 El Niño was one of the strongest on record, but its influence on the carbon balance is less clear. Using Northern Hemisphere atmospheric CO2 observations, we found both detrended atmospheric CO2 growth rate (CGR) and CO2 seasonal-cycle amplitude (SCA) of 2015−2016 were much higher than that of other El Niño events. The simultaneous high CGR and SCA were unusual, because our analysis of long-term CO2 observations at Mauna Loa revealed a significantly negative correlation between CGR and SCA. Atmospheric inversions and terrestrial ecosystem models indicate strong northern land carbon uptake during spring but substantially reduced carbon uptake (or high emissions) during early autumn, which amplified SCA but also resulted in a small anomaly in annual carbon uptake of northern ecosystems in 2015−2016. This negative ecosystem carbon uptake anomaly in early autumn was primarily due to soil water deficits and more litter decomposition caused by enhanced spring productivity. Our study demonstrates a decoupling between seasonality and annual carbon cycle balance in northern ecosystems over 2015−2016, which is unprecedented in the past five decades of El Niño events.

Original languageEnglish (US)
Pages (from-to)3798-3809
Number of pages12
JournalGlobal Change Biology
Volume27
Issue number16
DOIs
StatePublished - Aug 2021

All Science Journal Classification (ASJC) codes

  • Global and Planetary Change
  • Environmental Chemistry
  • Ecology
  • Environmental Science(all)

Keywords

  • atmospheric CO growth rate (CGR)
  • CO seasonal-cycle amplitude (SCA)
  • El Niño
  • net biome productivity (NBP)
  • northern terrestrial ecosystems
  • soil water deficit

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