| The effects of phytoplankton-induced changes in the attenuation of solar radiation in the ocean on the evolution of the surface, mixed layer and the heat exchange across the sea surface are examined in this study. A sensitivity analysis of the bulk (depth-integrated) class of mixed-layer models is used to explain the pathways through which the phytoplankton variability can influence the depth and temperature of the mixed layer. Conditions under which this influence can be expected to be significant are identified. The model equation for mixed-layer depth, common to all bulk models, is extended to take into account the spectral dependence of light transmission in the ocean as a function of phytoplankton biomass.;Changes in the potential energy of the upper ocean associated with vertical mixing are balanced against the TKE input to develop a general, bulk model of the oceanic mixed layer. The Kraus-Turner-type, bulk, mixed-layer models can be derived as special cases of this model. Moreover, the essential requirements, common to models of the Kraus-Turner-type, of a temperature discontinuity at the base of the mixed layer and the a priori existence of an initial mixed layer, are eliminated in the present formulation. A non-dimensional form of the general, bulk model is used to identify limitations inherent to conventional, bulk, mixed-layer models.;A coupled model of physical-biological interactions in the mixed layer, in the presence of air-sea heat exchange, is developed by combining the general, bulk model of the oceanic mixed layer with an energy-balance model of the atmosphere and a nitrogen-conserving model of net primary production in the mixed layer. This coupled model is used to examine the contributions from seasonal modulations in phytoplankton biomass to the evolution of mixed-layer depth, mixed-layer temperature, air temperature, and heat exchange across the sea surface for a hypothetical station at 50... |
