PARAMETER SENSITIVITY STUDY OF THE SALINE CIRCULATION

Saline circulation forced by fresh water alone is studied for a broad region of parameter space by varying the amplitude and profile of evap oration minus precipitation, the vertical and horizontal mixing of sal t, vertical and horizontal dissipation of momentum, and the horizontal resolution. The model is a modified Bryan-Cox model with a freshwater flux as the natural boundary condition for the salinity balance. For a model forced by a linear freshwater flux profile, as the amplitude o f freshwater flux is increased from 0.01 m year-1 to 1 m year-1 with o ther parameters fixed, the system evolves from a steady state of no os cillation to a state of periodic oscillation whose frequency increases almost linearly with the amplitude of freshwater flux. When the fresh water flux is fixed and the vertical mixing coefficient is increased f rom 0.5 to 2.5 cm2s-1, the system evolves from a steady state to a sta te of single-period oscillation, chaotic, a single period, and finally to a chaotic state when the vertical mixing coefficient is larger tha n 2 cm2s-1. One set of numerical experiments forced by a cosine shape of freshwater flux clearly reveals the transition from a state of sing le period oscillation to period doubling, period quadrupling, and a st ate of chaotic oscillation. Simple scaling analysis and numerical expe riments indicate that the strength of the meridional overturning incre ases with the square-root of the vertical mixing and the 1/4 power of the freshwater flux. The mean sea surface salinity (deviation from 35 psu) increases with the 3/4 power of the freshwater flux and decreases with the 1/2 power of the vertical salt mixing.