A sea surface height control dam at the Strait of Gibraltar

Global sea-level rise is now seen as one of the most significant impacts of human-induced climate change and is expected to seriously affect most coastal areas in the next 10–100 years. However, for the coasts of the Mediterranean Sea and Black Sea, a dam on the Strait of Gibraltar would provide long-term protection for at least the next few millennia. The dam would be designed to initially cause a height difference between its two sides of about a metre and allow inflow of Atlantic water to balance net evaporation. In addition to coastal protection, benefits of the dam include providing a land link between Europe and Africa, and power generation. Negative effects include possible large-scale changes in Atlantic Ocean flow, and perhaps climate, a long-term rise in Mediterranean salinity with eventual impacts on fisheries, and the need for shipping to pass through locks both at Gibraltar and Suez. The Mediterranean salinity rise would be slow, causing serious effects only after several centuries. Mitigation, when needed, would require pumping out large volumes of Mediterranean deep water, over or through the dam. The dam would be a major project, requiring international agreements and resources. It will probably not be built soon, but rising sea levels will make a dam ever more necessary, and discussions need to start to quantify costs, benefits and impacts. Copyright Her Majesty the Queen in Right of Canada as represented by: Fisheries and Oceans Canada 2015