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Sea Level Rise

storm surgesicon-caption
With a three- to four-foot increase in sea level, houses on the beach won't be the only ones vulnerable to severe damage. Higher seas will cause storm surges to travel farther inland, threatening buildings that once would have been a safe distance from the shore. (Photo courtesy of NOAA)

Sea level rise is an increase in the height of the ocean surface relative to land. Several factors can affect the height of the ocean surface: the amount of water in the ocean basins in the form of liquid water and ice; the temperature, and therefore the density and volume, of ocean water; and tectonic factors that affect the shape of ocean basins.

Other factors affect sea levels locally over short time scales, such as tides, storms, floods, and tsunamis. What is of most concern today is sea level rise driven by climate change, which affects both the amount and density of ocean water.

As air and water temperatures rise around the world, scientists are seeing more ice and meltwater moving from land-based sources on Antarctica and Greenland into the ocean. This adds to or displaces water in the ocean, raising the level of the entire ocean. In addition, as water temperatures rise, seawater expands.

These two factors have combined to produce a rise in sea level of 2 millimeters per year over the past century. The Intergovernmental Panel on Climate Change (IPCC) estimates that sea level may continue to rise as much as two feet over the next century.