Proceedings PaperCharacteristic Vertical Patterns Of Particles, Oxygen, And Chlorophyll Pigments In The North Pacific Gyre
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Characteristic vertical patterns of suspended particles, dissolved oxygen, and chlorophyll pigments in the North Pacific Gyre indicate that particle and oxygen maxima are found together in the upper part of the seasonal thermocline. The chlorophyll maximum is typically found 30 to 50 m below the particle maximum. The depth of the particle and oxygen maxima respond closely to changes in the mixed layer depth, but the chlorophyll maximum does not. The chlorophyll maximum is not only separated from the oxygen and particle maxima, but it is also little affected by changes in the surface mixed layer, suggesting that the chlorophyll maximum has its own origin different from that of the particle and oxygen maxima. Profiles of dissolved oxygen show that the high oxygen concentration layer extends to approximately 400 m, well below the euphotic zone, which points out that the primary source of the oxygen in this layer is the surface waters sunk in the high latitude Pacific and spread out in the gyre. Photosynthetical production of oxygen would be added on to the already oxygen rich water, but its net contribution appears relatively small since the oxygen concentration in the euphotic zone is not significantly higher than in the water below. Such a secondary role of the photosynthetic production of oxygen is also supported by the nutrient profiles; nutrient concentrations are uniformly low in the surface water down to the nutracline at approximately 120 m allowing only a low photosynthesis rate. The most significant change in the vertical pattern of beam attenuation coefficients is expected from the seasonal progress in the mixed layer since the attenuation maximum and the mixed layer are related.