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Equatorial upwelling in the eastern equatorial Pacific Ocean generates relatively cold temperatures and high iron concentrations in the surface ocean layer. The abundance of iron increases biological productivity in the eastern equatorial Pacific and leads to phytoplankton blooms, which in turn may affect the mixed-layer temperatures by an enhanced near-surface absorption of solar light. Here we use a simplified atmosphere-ocean model for the tropical Pacific to quantify the effect of ocean biology on tropical surface temperatures. It is shown that moderate phytoplankton blooms, occuring e.g. during La Nina conditions, lead to a vertical redistribution of heat in the surface layers of the eastern equatorial Pacific and an associated surface layer warming of about 20 W/m2. The positive air-sea coupling in the eastern equatorial Pacific plays an important role in amplifying this signal, thereby damping La Nina conditions. This temperature-regulating feedback acts as a biological thermostat within the surface ocean and influences also the amplitude and asymmetry of the El Nino-Southern Oscillation.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Axel Timmermann and Fei-Fei Jin "Biological feedback on El Nino and La Nina", Proc. SPIE 4899, Atmospheric and Oceanic Processes, Dynamics, and Climate Change, (14 April 2003);

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