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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L11609, doi:10.1029/2007GL030100, 2007

Impact of ocean color on the maintenance of the Pacific Cold Tongue

W. G. Anderson

Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, New Jersey, USA
NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA


A. Gnanadesikan

NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA


R. Hallberg

NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA


J. Dunne

NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA


B. L. Samuels

NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA


Abstract

The impact of the penetration length scale of shortwave radiation into the surface ocean is investigated with a fully coupled ocean, atmosphere, land and ice model. Oceanic shortwave radiation penetration is assumed to depend on the chlorophyll concentration. As chlorophyll concentrations increase the distribution of shortwave heating becomes shallower. This change in heat distribution impacts mixed-layer depth. This study shows that removing all chlorophyll from the ocean results in a system that tends strongly towards an El Niño state—suggesting that chlorophyll is implicated in maintenance of the Pacific cold tongue. The regions most responsible for this response are located off-equator and correspond to the oligotrophic gyres. Results from a suite of surface chlorophyll perturbation experiments suggest a potential positive feedback between chlorophyll concentration and a non-local coupled response in the fully coupled ocean-atmosphere system.

Received 21 March 2007; accepted 11 May 2007; published 12 June 2007.

Keywords: ocean modeling; climate; chlorophyll.

Index Terms: 3339 Atmospheric Processes: Ocean/atmosphere interactions (0312, 4504); 4255 Oceanography: General: Numerical modeling (0545, 0560); 4263 Oceanography: General: Ocean predictability and prediction (3238); 4264 Oceanography: General: Ocean optics (0649); 4922 Paleoceanography: El Nino (4522).

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Citation: Anderson, W. G., A. Gnanadesikan, R. Hallberg, J. Dunne, and B. L. Samuels (2007), Impact of ocean color on the maintenance of the Pacific Cold Tongue, Geophys. Res. Lett., 34, L11609, doi:10.1029/2007GL030100.