A highly simplified coastal ocean model is constructed for central California during the middle to late Miocene (13--6 million years ago). Central California was a semienclosed shallow basin during that time, communicating with the open North Pacific Ocean. Surface temperatures for the basin have been derived using Tertiary fossil mollusks and siliceous deposits. The model provides qualitative information for reconstructing paleoclimatic and paleoceanic conditions. It is based on spatially two-dimensional equations for the velocity and temperature in a single layer of shallow fluid. The model domain consists of a rectangular coastal basin partially connected to a portion of the Pacific Ocean. The wind stress is assumed to be spatially constant from a given direction. The flow in and out of the basin is driven by the bottom topography torque due to depth variation between basin and ocean. The temperature of the open ocean is prescribed. The temperature of the basin is governed by the relative influence of this oceanic temperature and the atmospheric reference temperature, to which vertical fluxes drive the basin in the absence of dynamical influences. Two different boundaries are used: fully open or semiopen, with a partial barrier between the basin and the ocean. We examine scenarios with different barrier extents, with openings to the ocean at one or both ends of the basin, and with different assumptions about the wind direction and currents. The effect of adding a second model layer is also investigated. We found that the results are quite insensitive to assumptions about the paleowind stress. The semiopen model appears closest to the paleocean data. This argues for the presence of a barrier during the late Miocene between the central California basin and the open ocean, at least in the basin's northern part. ¿ American Geophysical Union 1993