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Title: Biophysical coupling in the ocean mixed layer
Author: Robertson, Edward
ISNI:       0000 0004 2743 0000
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2011
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Sea surface temperature (SST) controls surface fluxes of heat and moisture and so helps determine the state of the atmosphere, particularly in the tropics. Chlorophyll modulates the absorption of shortwave radiation and modelling studies have shown that chlorophyll concentration affects SST. A hierarchy of 1-dimensional mixed layer models is used to identify and quantify the mechanisms by which chlorophyll concentration affects SST. Idealised simulations show that changes in chlorophyll concentration affect the stability of the water column, and so the depth of the mixed layer. The mixed layer depth affects entrainment, the radiative heating of the mixed layer and the heat capacity of the mixed layer. Seasonal timescale simulations of the Arabian Sea and west Pacific warm pool are made using the K-Profile Parameterization (KPP) model. Air-sea interactions are important in these locations and together the regions cover a wide range of biological and physical conditions. The mixed layer response to observed and interactively simulated chlorophyll concentrations is studied. The response of the mixed layer depth to chlorophyll variability causes a negative feedback on the heating response to chlorophyll variability through changes in radiative heating and in the heat capacity of the mixed layer. Seasonal chlorophyll variability is found to have an important affect on SST. Variability on shorter timescales has little impact because, several weeks are required for an SST anomaly to accumulate and, SST anomalies do not persist through deep mixing events. It is concluded that satellite observations of the seasonal cycle of chlorophyll should be applied to global ocean models to improve their simulation of SST. Further investigation is needed to understand the roles of nutrient advection and air- sea interactions in controlling the SST response to chlorophyll variability. To do this a 3-dimensional biophysical ocean-atmosphere model with high vertical resolution in the mixed layer should be used.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available