Sea-Level Rise: Causes, Impacts, and Scenarios for Change

Studies of sea-level changes (SLCs) are well established, as is reflected in an extensive research and wider publication literature. People globally have long recognized that ancient marine shorelines and beach sediments occur inland, well away from present day coasts. The causes of SLC center upon a series of primary controls resulting from the operation of an integrated atmosphere-ocean system. These include changes in the total water volume of the oceans over time, temperature effects on ocean water expansion, alterations in the shape of the ocean basins from Earth crustal movements, and changes in their accommodation space through sediment accumulation. Satellite surveys also show that the topography of the oceans and shelf seas is influenced by gravitational controls, which define the Earth geoid, with an up to 180. m difference in interregional sea surface heights. In the Quaternary, past glaciations have driven sea levels to approximately -120. m global mean sea level (gmsl). The significance of SLC today lies in establishing an understanding and projections of how sea levels will change in the future. Climate warming during the twenty-first century will result in the melting of the Earth's remaining ice masses, with gmsls likely to rise at rates of 4-5. mm/year by 2050, reaching levels of 0.5-0.9. m by 2100 under differing Intergovernmental Panel on Climate Change (IPCC) global warming scenarios. The impacts of these movements will potentially result in initial losses of up to 30% of coastal wetlands and an increasing "squeeze" of people and biological systems into the reorganizing coastal zone.