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Inter Annual Variability of the California Current System and Associated Biochemical Characteristics from Prolonged Data Series

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Naval Postgraduate School Monterey United States

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This research investigates the California Current System CCS utilizing Synoptic Monthly Gridded World Ocean database SMG-WOD for temperature and salinity profiles, MODIS-A for surfacechlorophyll-a Chl-a concentration, and climatological indices El Nino Modoki Index EMI and Multivariate El Nino Southern Oscillation Index MEI, to compare inter-annual variations. The SMGWOD produces 3D gridded fields with 11 horizontal resolution and 28 vertical layers. The area of interest was 0 deg54N, 165W105W from January 1945December 2014. Because processes within 50km of the coast are not well resolved by SMG-WOD, Chl-a data from MODIS-A with a 4.6 km resolution was used from July 2002December 2014. Acceleration potential at the isopycnal surface of theta 26.9 kgm3 relative to the 1000 dbar was calculated from the SMG-WOD. Composite and Empirical Orthogonal Function EOF analysis was conducted to identify patterns of maximum variance. Correlation coefficients were calculated to determine connections between inter-annual variability and EMIMEI. Acceleration potential had small seasonal variability, while Chl-a concentration demonstrated large seasonal variability. When Principal Component PC 1 is positive, EMI index will be negative, resulting in an increased geostrophic flow in the CCS. For positive PC2, MEI is negative resulting in an offshore flow and thus enhanced coastal upwelling in the CCS. Positive PC1 correspond to negative EMIMEI and elevated surface Chl-a concentration in the CCS.

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Approved For Public Release;

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