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Studies of Chlorophyll Dynamics using Moored Irradiance Sensors

  • Author(s): Wilson, Samuel Johnson
  • Advisor(s): Send, Uwe
  • et al.
Abstract

Understanding oceanic chlorophyll dynamics requires new measurement methods and novel analyses. Moored irradiance sensors provide long time series of diffuse attenuation, and through a technique developed here, can provide estimates of average chlorophyll concentration between the sensors. This technique is applied to the California Current Ecosystem moorings, where simultaneous current measurements coupled with the chlorophyll time series describe chlorophyll transport. Cross-shore transport events occur on timescales longer than 25 days in the offshore site, and account for offshore chlorophyll transport of 31.20 g/(day) per meter of coastline. In the near shore site, successive upwelling events transport large amounts of chlorophyll offshore, while single upwelling events do not. In total, events account for 94.80 g/(day) offshore chlorophyll transport per meter of coastline at this site. The method is then applied to recover 9 years of 0-9m chlorophyll concentration estimates in the Northwestern Mediterranean Sea. This region is dominated by a spring chlorophyll bloom, and the chlorophyll model used describes interannual variability in the initiation of this event by 25 days or more. During the bloom, hiatuses can occur where the 0-9m chlorophyll concentration decreases due to mixing, and they are often associated with Spring cooling events. The date of the last cooling event in January to April is a significant determinant of the delay in the 0-9m signature of the Spring Chlorophyll Bloom.

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