A new study says sea level may rise faster than scientists currently project. That's because dams built in the 20th century have captured and stored a great deal of water on land. That has slowed the rate of sea level rise and masked the effect of expanding seawater and melting ice. The study suggests that ice has actually been melting faster than we've realized. Current estimates, of a foot or two of sea level rise by the end of the century, could be low by several feet.