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Water Mass Variability, Nutrients, Sediments, and Phytoplankton Pigment
Concentrations in the Santa Barbara Channel

Michael J. Neumann, D.A. Toole, N.L. Cohn, L. Washburn, and D.A. Siegel
Institute for Computational Earth System Science, University of California, Santa Barbara

The Plumes and Blooms project is a coordinated time series project of field observations and satellite imagery analysis with the goal of understanding the driving mechanisms and impacts of sediment plumes and phytoplankton blooms in the Santa Barbara Channel. Beginning in August of 1996, optical measurements, with corresponding physical, chemical, and biological sampling, have been made twice monthly along a seven station transect across the Santa Barbara Channel. A large range of environmental conditions have been sampled in the first two years of the project. Utilizing principle component analysis, we investigate the covariance among water mass, nutrient concentration, and response of phytoplankton populations to varying environmental regimes. The first four modes of variability account for 81% of the total variance and represent conditions consistent with upwelled waters (40%), bloom conditions (18%), plume waters (12%), and high salinity waters (11%). This work provides a context from which to interpret our ocean-color modeling and analysis efforts.

Analysis

Goal: Asess covariance among water mass properties, nutrients, sediments, and biomass indicators to characterize plume versus bloom water.

• Use principle components to identify and quantify modes of variability.

• Correlate modes with parameters to asses the discrete composition of each mode.

Values above bars represent r^2 between parameter and mode.

Interpretation of Analysis

The first four modes explain 81% of the variance.

• Mode 1 - "Upwelling Mode"

  Explains 40% of variance.
  Highly correlated with temperature, nutirents, and biomass indicators.
  Inverse correlation between temperature and nutrients.
  Positive correlation between nutrients and biomass indicators.
  

• Mode 2 - "Bloom Mode"

  Explains 18% of variance.
  Predominantly correlated with nutrients and biomass indicators.
  Inverse relationship between biomass indicators and nutrients.
  Low nutrient, high biomass relationship suggests bloom conditions.
  

• Mode 3 - "Plume Mode"

  Explains 12% of variance.
  Highly correlated with lithogenic silica and total suspended materila concentrations.
  High lithogenic silica and total suspended material relationship suggests plume conditions.
  

• Mode 4 - "Salinity Mode"

  Explains 11% of variance.
  Highly correlated with salinity.
  May represent influence of water of more subtropical origin (i.e. water from San Pedro Basin) or signal from 1998 El Nino.

Conclusions

Developed principle component modes for identifying major sources of variability in water properties of the Santa Barbara Channel.

• Modes are identified as: Upwelling (40%), Bloom (18%), Plume (12%), and Salinity (11%).

• Analysis provides a context from which to interpret ocean-color modeling and analysis efforts.