arming temperatures contribute to sea level rise by: expanding ocean water; melting mountain glaciers and ice caps; and causing portions of the Greenland and Antarctic ice sheets to melt or flow into the ocean.[3]
Since 1870, global sea level has risen by about 7.5 inches.[2] Estimates of future sea level rise vary for different regions, but global sea level for the next century is expected to rise at a greater rate than during the past 50 years.[2] Studies project global sea level to rise by another 1 to 4 feet by 2100, with an uncertainty range of 0.66 to 6.6 feet.[1]
The contribution of thermal expansion, ice caps, and small glaciers to sea level rise is relatively well studied, but the impacts of climate change on ice sheets in Greenland and Antarctica are less understood and represent an active area of research. Changes in ice sheets are currently expected to account for 1.2 to 8 inches of sea level rise by the end of this century.[3]
Graph displaying past and projected changes in global sea level. Proxy records from 1800-1875 show -0.5ft; tide gauge data increase from -0.5ft in 1875 to 0.2 in 1980, satellite data show an increase to 0.3ft in 2005, and projections range 1-4ft by 2100.
Past and projected sea level rise from 1800 to 2100. The orange line at right shows the currently projected range of sea level rise of 1 to 4 feet by 2100; the wider range (0.66 feet to 6.6 feet) reflects uncertainty about how glaciers and ice sheets will react to climate change. Source: NCA, 2014.
Click the image to view a larger version.
Regional and local factors will influence future relative sea level rise for specific coastlines around the world. For example, relative sea level rise depends on land elevation changes that occur as a result of subsidence (sinking) or uplift (rising). Assuming that these historical geological forces continue, a 2-foot rise in global sea level by 2100 would result in the following relative sea level rise:[4]
2.3 feet at New York City
2.9 feet at Hampton Roads, Virginia
3.5 feet at Galveston, Texas
1 foot at Neah Bay in Washington state
Relative sea level rise also depends on local changes in currents, winds, salinity, and water temperatures, as well as proximity to thinning ice sheets.[2]