A simple model of a northern ocean with eastern boundary slope current (Q2732516)

A simple model is constructed to describe how an eastern boundary slope current interacts with a large-scale ocean circulation. The model assumes that the main variation in surface temperature occurs in the latitudinal direction with only weak variation in zonal direction. The assumed surface temperature distribution is in reasonable agreement with observations in North Atlantic or North Pacific. The influence of this weak zonal variation on the surface temperature is identified by comparison with the solution without zonal variation in surface temperature. A simple steady model of ocean circulation in the northern hemisphere (based on the thermocline equations) is used with an appropriate condition at the eastern boundary of the ocean to represent the influence of the slope current on the ocean circulation. The detailed dynamics of the slope current is not resolved, but the influence of ocean circulation on the slope current is taken into account. The influence of the eastern slope current on the ocean circulation is simulated by assigning a non-zero value to the integrated mass transport at the eastern boundary of the ocean. The solution is obtained for a tropical region extending from the equator to a subtropical region, and for a subpolar region. The authors show that the value of vertical thermal diffusion coefficient is critically important in determining a realistic distribution of temperature in the ocean, and in determining the mass transported across the eastern boundary of the ocean. It is shown that the longitudinal variation in surface temperature is necessary for the determination of the temperature field in the interior of ocean to display the observed upward bowing of isotherms towards the east in tropical-subtropical ocean, and the downward bowing of isotherms towards the east in subpolar ocean. However, the authors demonstrate that only in the tropical region the velocity field is significantly affected by the longitudinal variation in temperature, and that in the subtropical-subpolar ocean acceptably good approximations to the velocity field result from using a zonally averaged temperature field.