Initiation of new ice sheet growth is of great concern because the strong positive feedback of enhanced albedo and heavier cloud cover, much like the effectiveness of cloudiness over the Greenland Ice Sheet today, might lock in the ice-age growth mode despite CO 2 warming. The ultimate consequence might be a combination of two extremes. The diversion of North Atlantic Drift water as a function of the Mediterranean outflow is difficult to measure accurately because of the complex and fluctuating currents within the northern gyre. Quantitative verification of the fluidic switch model is therefore difficult. The counterflow exchange of salt is greatly minimized by separating most of the surface inflow from the deeper Mediterranean outflow water entering the Atlantic.
Bathymetry is in meters.
A bridge over the central outflow opening would complete the link between Spain and Africa. For a few hundred years after completion of the Gibraltar dam and before Mediterranean salinity reaches a new approximate steady state, this source of salt would be greatly reduced. This would tend to maintain sea-ice coverage as CO 2 warming progresses, and prevent or delay melting of the West Antarctic Ice Sheet and world coastal flooding. The construction of the Gibraltar Dam may be both politically and technically feasible, but the scale of the dam is large, and construction would require an unprecedented effort probably over many decades. The profile of a suggested dam configuration is shown in Figure 3b.