A process-oriented modelling study of the coastal Canary and Iberian Current system

In a hierarchy of increasing complexity of physical forcing mechanisms, we conduct a process-oriented study of the Northern Canary Current System (NCCS) with a terrain-following numerical ocean model (in this case the Princeton Ocean Model, POM) to investigate the forcing mechanisms for the classical as well as unique features of the NCCS. While most of the NCCS features are realistically simulated, a key comparison of the results shows that unexpectedly a realistic subsurface mesoscale feature is simulated in a flat bottom NCCS model but not in the same model with bottom topography. We then show that this is a consequence of a numerical choice, which leads to the use of an improved technique to smooth the bottom topography, which better preserves the raw topography and subsequently is shown to produce the subsurface feature. This choice is then used in the final and most realistic of the NCCS experiments, in which a high temporal resolution study is conducted from March to September 1996 for the NCCS coastal ocean domain using daily winds and thermohaline forcing initialized on 2 March 1996 from a one-way coupled North Atlantic Parallel Ocean Program (POP) model updated at the lateral boundaries of the POM model every three days. A key physical result is that a dynamic flow consistent with the Azores Current is produced in this experiment, a feature not produced in the other experiments which used climatological data at the open boundaries. The results of these process-oriented experiments emphasize that numerical models of ocean circulation require important choices, which are both numerical and physical.