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Sea levels will continue to rise, warn scientists

Sea levels will continue to rise, warn scientists - Ocean levels on Earth have risen an average of 3 inches in the last 23 years, and could rise an additional 3 feet in the next century, according to NASA scientists charged with measuring changing sea levels.

According to Steve Nerem, a scientist at the University of Colorado, Boulder, about one-third of the rising sea level is a result of the ocean expanding as it absorbs heat trapped by greenhouse gases and becomes warmer. Another third comes from melting glaciers, and the rest comes from the melting of massive ice sheets in Antarctica and Greenland.

During the last decade, Antarctica's ice sheet lost about 118 gigatons annually on average, while Greenland's ice sheet lost about 303 gigatons of ice on average each year.

However, waters off the coast of western U.S. have had lower surface temperatures, mainly because of the Pacific Decadal Oscillation (PDO). This pattern of ocean current, wind and temperature variations can bring cold or warm phases for many years. Since 1998, some scientists said we have experienced a cold phase that has undermined the effects of climate change and prevented sea levels from rising.

Scientists have said that a reversal in the PDO could cause sea levels to increase seen elsewhere. Current measurements point that a switch in the PDO already occurred, according to JPL's Willis.

Some scientists think of El Nino as a short-term phenomenon that lies on top of the more long-term temperature fluctuations linked with the PDO. Warmer PDOs are more conducive to El Ninos.

Tom Wagner, who is a cryosphere program manager for NASA, said communities along coastal areas should factor in the increase in sea levels when considering infrastructure projects such as a power plant or water treatment plant.