EGU2020-11256, updated on 19 Apr 2021
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Inter-annual predictability of net primary productivity in the central equatorial Pacific

Sebastian Brune1, Maria Caballero Espejo1,2, Hongmei Li3, Tatiana Ilyina3, and Johanna Baehr1
Sebastian Brune et al.
  • 1Institute of Oceanography, Universität Hamburg, Hamburg, Germany (
  • 2General Office of Climate Change and Desertification, Ministry of Environment of Peru, Magdalena del Mar, Peru
  • 3Max Planck Institute for Meteorology, Hamburg, Germany

We analyse central equatorial Pacific inter-annual prediction skill of sea surface temperature (SST) and net primary productivity (NPP) using initialized retrospective forecasts with the Max Planck Institute Earth system model over the time period 1998-2014. We find significant NPP predictability for up to 5 lead years, which is far beyond the SST predictability of less than 1 year in this area. While El-Nino-Southern-Oscillation (ENSO) limits SST predictability, we find the origin of the high NPP prediction skill to be in the tropical upwelling zones of the eastern Pacific, i.e., the Peru-Chile current system offshore South America. Off-equatorial Rossby waves are initiated off the coast of Chile and travel towards the central tropical Pacific on a time scale of 4 to 5 years. On their arrival, the Rossby waves modify the depth of the nutricline, which is fundamental to the availability of nutrients in the euphotic layer in the central tropical Pacific.

We further demonstrate that the seasonal upwelling in the central equatorial Pacific, which is mainly driven by ENSO, transports nutrients, i.e. nitrate and phosphate, from below the nutricline into the euphotic zone, effectively transferring the Rossby wave signal from depth to the near-surface ocean. A shallower than normal nutricline leads to larger primary production, and vice versa, a deeper than normal nutricline to smaller primary production. The Rossby waves also modulate the SST, however, these changes are damped on the daily to weekly time scale due to surface heat fluxes at the atmosphere-ocean boundary. Therefore, the off-equatorial Rossby waves maintain the high predictability of NPP but not the SST. We conclude that NPP predictions in the central equatorial Pacific benefit from the memory contained in properly simulated off-equatorial Rossby waves.

How to cite: Brune, S., Caballero Espejo, M., Li, H., Ilyina, T., and Baehr, J.: Inter-annual predictability of net primary productivity in the central equatorial Pacific, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11256,, 2020.


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