The Gulf Stream and the Past, Present and Future of Ocean Models

The Gulf Stream provides a continuing research challenge and is the ultimate test bed for ocean climate models. The Gulf Stream and its extension the North Atlantic Current inspired the first attempts to formulated mathematical models of the ocean circulation. The evolution of models since the beginning of modern oceanography can be traced through attempts to improve simulations and scientific understanding of this magnificent phenomenon. The earliest numerical models were merely extensions of analytic studies and contained a minimum of physics. Over time methods borrowed from numerical weather forecasting allowed more ambitious models that included more three-dimensional structure, but were still limited in horizontal resolution. At the same time measurements produced a much more complex picture of the Gulf Stream. The discovery of mesoscale eddies indicated that the Gulf Stream was a true analogue of the atmospheric jet stream, but much more difficult to observe. The Gulf Stream is the upper branch of the meridional overturning of the North Atlantic, a major mechanism for poleward heat transfer. There has been a growing realization in the last decade that variations in the meridional overturning in the North Atlantic plays a major role global climate variations on a multi-decadal time-scale. The community is now engaged in ocean data assimilation and making decadal forecasts of the coupled models of the World Ocean. Increased horizontal resolution of ocean models, coupled with a better understanding of the the interaction of currents with bathymetry and polar water mass formation, are a key to future progress in modeling the Gulf Stream system and making decadal climate projections in the North Hemisphere climate.