Articles | Volume 22, issue 5
https://doi.org/10.5194/os-22-2973-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-22-2973-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Chlorophyll a concentration effects on equatorial Atlantic Ocean mean-state and interannual variability
Arthur Prigent
CORRESPONDING AUTHOR
The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy
now at: Univ Brest, CNRS, Ifremer, IRD, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM, 29280 Plouzané, France
Riccardo Farneti
The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy
Manfredi Manizza
Oceanography Section, National Institute of Oceanography and Applied Geophysics – OGS, Trieste, Italy
Rodrigue Anicet Imbol Koungue
Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
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Geosci. Model Dev., 19, 867–885, https://doi.org/10.5194/gmd-19-867-2026, https://doi.org/10.5194/gmd-19-867-2026, 2026
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Revised manuscript under review for ESSD
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Editorial statement
While it is normally understood that marine biogeochemical processes strongly depend on the physical drivers, but less so in the converse, here the authors demonstrate that nonlinear responses are present in a series of experiments that modify the absorption rate of light based on chlorophyll concentrations. While the leading order mechanism is clear (more absorption, less radiative forcing on the ocean), the more detailed governing mechanisms for the oceanic response are less obvious, and the authors provide some investigations towards that end with a focus on tropical regions. They also suggest that the ongoing observed decrease in tropical Atlantic chlorophyll-a concentration may weaken the interannual variability of sea surface temperature.
While it is normally understood that marine biogeochemical processes strongly depend on the...
Short summary
Ocean model simulations with chlorophyll-a scaled from 0.01–2× climatology show that low chlorophyll (“clear ocean”) warms the eastern equatorial Atlantic by 0.15 °C, weakens vertical temperature gradients, deepens the mixed layer, and reduces equatorial upwelling. These changes reduce the sea surface temperature (SST) seasonal cycle by 14% and interannual variability by 12.9%, suggesting that a decline in tropical Atlantic chlorophyll may weaken SST variability.
Ocean model simulations with chlorophyll-a scaled from 0.01–2× climatology show that low...