New research presented at this week's annual meeting of the Geological Society of America shows that rising sea levels of as little as a half-meter per century have been sufficient to dramatically change the shoreline of the U.S. Gulf Coast within the past 10,000 years. The findings are significant because half-meter increases are within the moderate range of predictions for the Gulf Coast during this century.

"About 5,000 years ago, when sea level was rising approximately 50 centimeters per century, the upper part of Corpus Christi Bay increased by about one third over the span of about 200 years," said John Anderson, the W. Maurice Ewing Chair in Oceanography and professor of earth science at Rice University in Houston. "Even without factoring in any effects from global warming, that's only about 20 percent slower than the projected sea level increases along the Texas and Louisiana coasts this century."

Scientists know from oceanographic records that sea level has been rising worldwide for at least 10,000 years. The exact cause is unknown, but the rates of rise for specific eras have been well documented from marine sedimentary records worldwide. Scientists know, for example, that rates of sea level rise have gradually fallen from more than 100 centimeters per century 10,000 years ago to about 20 centimeters per century today -- a rate that's been confirmed using global tide gauge records from the past 100 years.

But the trend toward slowing rates of sea level rise is expected to reverse this century, as global warming pushes rates back up. According to estimates by the International Panel for Climate Change, rising ocean temperatures this century will add about 30 centimeters to sea level, and glacial runoff from Antarctica -- the least understood of all the phenomena involved -- could add another 40 centimeters. Thus, the worst-case scenario could translate into a 90-centimeter boost in sea level by 2100-- a rate of increase that global c
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Contact: Jade Boyd
jadeboyd@rice.edu
713-348-6778
Rice University
8-Nov-2004

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