Articles | Volume 18, issue 14
Atmos. Chem. Phys., 18, 10333–10345, 2018

Special issue: The 10th International Carbon Dioxide Conference (ICDC10)...

Atmos. Chem. Phys., 18, 10333–10345, 2018

Research article 19 Jul 2018

Research article | 19 Jul 2018

Contrasting interannual atmospheric CO2 variabilities and their terrestrial mechanisms for two types of El Niños

Jun Wang1,2, Ning Zeng2,3, Meirong Wang4, Fei Jiang1, Jingming Chen1,5, Pierre Friedlingstein6, Atul K. Jain7, Ziqiang Jiang1, Weimin Ju1, Sebastian Lienert8,9, Julia Nabel10, Stephen Sitch11, Nicolas Viovy12, Hengmao Wang1, and Andrew J. Wiltshire13 Jun Wang et al.
  • 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, Maryland, 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
  • 5Department of Geography, University of Toronto, Toronto, Ontario M5S3G3, Canada
  • 6College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK
  • 7Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
  • 8Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
  • 9Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 10Land in the Earth System, Max Planck Institute for Meteorology, 20146 Hamburg, Germany
  • 11College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UK
  • 12Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL-CEA-CNRS-UVQS, 91191, Gif-sur-Yvette, France
  • 13Met office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB, UK

Abstract. El Niño has two different flavors, eastern Pacific (EP) and central Pacific (CP) El Niños, with different global teleconnections. However, their different impacts on the interannual carbon cycle variability remain unclear. Here we compared the behaviors of interannual atmospheric CO2 variability and analyzed their terrestrial mechanisms during these two types of El Niños, based on the Mauna Loa (MLO) CO2 growth rate (CGR) and the Dynamic Global Vegetation Model's (DGVM) historical simulations. The composite analysis showed that evolution of the MLO CGR anomaly during EP and CP El Niños had three clear differences: (1) negative or neutral precursors in the boreal spring during an El Niño developing year (denoted as yr0), (2) strong or weak amplitudes, and (3) durations of the peak from December (yr0) to April during an El Niño decaying year (denoted as yr1) compared to October (yr0) to January (yr1) for a CP El Niño, respectively. The global land–atmosphere carbon flux (FTA) simulated by multi-models was able to capture the essentials of these characteristics. We further found that the gross primary productivity (GPP) over the tropics and the extratropical Southern Hemisphere (Trop + SH) generally dominated the global FTA variations during both El Niño types. Regional analysis showed that during EP El Niño events significant anomalous carbon uptake caused by increased precipitation and colder temperatures, corresponding to the negative precursor, occurred between 30° S and 20° N from January (yr0) to June (yr0). The strongest anomalous carbon releases, largely due to the reduced GPP induced by low precipitation and warm temperatures, occurred between the equator and 20° N from February (yr1) to August (yr1). In contrast, during CP El Niño events, clear carbon releases existed between 10° N and 20° S from September (yr0) to September (yr1), resulting from the widespread dry and warm climate conditions. Different spatial patterns of land temperatures and precipitation in different seasons associated with EP and CP El Niños accounted for the evolutionary characteristics of GPP, terrestrial ecosystem respiration (TER), and the resultant FTA. Understanding these different behaviors of interannual atmospheric CO2 variability, along with their terrestrial mechanisms during EP and CP El Niños, is important because the CP El Niño occurrence rate might increase under global warming.

Short summary
Based on the Mauna Loa CO2 records and TRENDY multi-model historical simulations, we investigate the different impacts of EP and CP El Niños on interannual carbon cycle variability. Composite analysis indicates that the evolutions of CO2 growth rate anomalies have three clear differences in terms of precursors (negative and neutral), amplitudes (strong and weak), and durations of peak (Dec–Apr and Oct–Jan) during EP and CP El Niños, respectively. We further discuss their terrestrial mechanisms.
Final-revised paper