NPG Nonlinear Processes in Geophysics NPG Nonlin. Processes Geophys. 1607-7946 Copernicus Publications Göttingen, Germany 10.5194/npg-18-29-2011 Interactions between marine biota and ENSO: a conceptual model analysis Heinemann M. 1 Timmermann A. 2 Feudel U. 3 Max Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg, Germany IPRC and Dept. of Oceanography, SOEST, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA ICBM, C. v. O. University of Oldenburg, Carl von Ossietzky Strasse 9–11, 26111 Oldenburg, Germany 21 01 2011 18 1 29 40 Copyright: © 2011 M. Heinemann et al. 2011 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://npg.copernicus.org/articles/18/29/2011/npg-18-29-2011.html The full text article is available as a PDF file from https://npg.copernicus.org/articles/18/29/2011/npg-18-29-2011.pdf

We develop a conceptual coupled atmosphere-ocean-ecosystem model for the tropical Pacific to investigate the interaction between marine biota and the El Niño-Southern Oscillation (ENSO). Ocean and atmosphere are represented by a two-box model for the equatorial Pacific cold tongue and the warm pool, including a simplified mixed layer scheme. Marine biota are represented by a three-component (nutrient, phytoplankton, and zooplankton) ecosystem model. <br><br> The atmosphere-ocean model exhibits an oscillatory state which qualitatively captures the main physics of ENSO. During an ENSO cycle, the variation of nutrient upwelling, and, to a small extent, the variation of photosynthetically available radiation force an ecosystem oscillation. The simplified ecosystem in turn, due to the effect of phytoplankton on the absorption of shortwave radiation in the water column, leads to (1) a warming of the tropical Pacific, (2) a reduction of the ENSO amplitude, and (3) a prolongation of the ENSO period. We qualitatively investigate these bio-physical coupling mechanisms using continuation methods. It is demonstrated that bio-physical coupling may play a considerable role in modulating ENSO variability.

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