Journal cover Journal topic
Earth System Dynamics An interactive open-access journal of the European Geosciences Union

Journal metrics

  • IF value: 3.635 IF 3.635
  • IF 5-year<br/> value: 3.869 IF 5-year
  • CiteScore<br/> value: 4.15 CiteScore
  • SNIP value: 0.995 SNIP 0.995
  • SJR value: 2.742 SJR 2.742
  • IPP value: 3.679 IPP 3.679
  • h5-index value: 21 h5-index 21
Earth Syst. Dynam., 9, 1-14, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
11 Jan 2018
Contrasting terrestrial carbon cycle responses to the 1997/98 and 2015/16 extreme El Niño events
Jun Wang1,2, Ning Zeng2,3, Meirong Wang4, Fei Jiang1, Hengmao Wang1, and Ziqiang Jiang1 1International Institute for Earth System Science, Nanjing University, Nanjing, China
2State Key Laboratory of Numerical Modelling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Beijing, China
3Department of Atmospheric and Oceanic Science and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
4Joint Center for Data Assimilation Research and Applications/Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science & Technology, Nanjing, China
Abstract. Large interannual atmospheric CO2 variability is dominated by the response of the terrestrial biosphere to El Niño–Southern Oscillation (ENSO). However, the behavior of terrestrial ecosystems differs during different El Niños in terms of patterns and biological processes. Here, we comprehensively compare two extreme El Niños (2015/16 and 1997/98) in the context of a multi-event composite El Niño. We find large differences in the terrestrial carbon cycle responses, even though the two events were of similar magnitude.

More specifically, we find that the global-scale land–atmosphere carbon flux (FTA) anomaly during the 1997/98 El Niño was 1.64 Pg C yr−1, but half that quantity during the 2015/16 El Niño (at 0.73 Pg C yr−1). Moreover, FTA showed no obvious lagged response during the 2015/16 El Niño, in contrast to that during 1997/98. Separating the global flux by geographical regions, we find that the fluxes in the tropics and extratropical Northern Hemisphere were 1.70 and −0.05 Pg C yr−1 during 1997/98, respectively. During 2015/16, they were 1.12 and −0.52 Pg C yr−1, respectively. Analysis of the mechanism shows that, in the tropics, the widespread drier and warmer conditions caused a decrease in gross primary productivity (GPP; −0.73 Pg C yr−1) and an increase in terrestrial ecosystem respiration (TER; 0.62 Pg C yr−1) during the 1997/98 El Niño. In contrast, anomalously wet conditions occurred in the Sahel and East Africa during 2015/16, which caused an increase in GPP, compensating for its reduction in other tropical regions. As a result, the total 2015/16 tropical GPP and TER anomalies were −0.03 and 0.95 Pg C yr−1. GPP dominance during 1997/98 and TER dominance during 2015/16 accounted for the phase difference in their FTA. In the extratropical Northern Hemisphere, the large difference occurred because temperatures over Eurasia were warmer during the 2015/16, as compared with the cooling seen during the 1997/98 and the composite El Niño. These warmer conditions enhanced GPP and TER over Eurasia during the 2015/16 El Niño, while these fluxes were suppressed during 1997/98. The total extratropical Northern Hemisphere GPP and TER anomalies were 0.63 and 0.55 Pg C yr−1 during1997/98, and 1.90 and 1.45 Pg C yr−1 during 2015/16, respectively. Additionally, wildfires played a less important role during the 2015/16 than during the 1997/98 El Niño.

Citation: Wang, J., Zeng, N., Wang, M., Jiang, F., Wang, H., and Jiang, Z.: Contrasting terrestrial carbon cycle responses to the 1997/98 and 2015/16 extreme El Niño events, Earth Syst. Dynam., 9, 1-14,, 2018.
Publications Copernicus
Short summary
Behaviors of terrestrial ecosystems differ in different El Niños. We analyze terrestrial carbon cycle responses to two extreme El Niños (2015/16 and 1997/98), and find large differences. We find that global land–atmosphere carbon flux anomaly was about 2 times smaller in 2015/16 than in 1997/98 event, without the obvious lagged response. Then we illustrate the climatic and biological mechanisms of the different terrestrial carbon cycle responses in 2015/16 and 1997/98 El Niños regionally.
Behaviors of terrestrial ecosystems differ in different El Niños. We analyze terrestrial carbon...