Scientists find drop in global sea level

The Washington Post | August 27, 2011
By Juliet Eilperin

The global sea level this summer is a quarter of an inch lower than last summer, according to NASA scientists, in sharp contrast to the gradual rise the ocean has experienced in recent years.

The change stems from two strong weather cycles over the Pacific Ocean — El Niño and La Niña — which shifted precipitation patterns, according to scientists at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. The two cycles brought heavy rains to Brazil and Amazon, along with drought to the southern United States.

Researchers monitored the ocean’s width, height, temperature and salinity through satellites and robot-operated floats, and presented their findings Aug. 8 and 9 at the annual Gravity Recovery and Climate Experiment (GRACE) Science Team Meeting in Austin, Tex.

“This year the continents got an extra dose of rain, so much so that global sea levels actually fell over most of the last year,” said Carmen Boening, an oceanographer and climate scientist at the lab.

Josh Willis, who also works at NASA’s Jet Propulsion Laboratory, warned that this water will eventually return to the ocean, and the long-term trend of rising sea levels will continue.

“What this show is the impact La Nina and El Niño can have on global rainfall,” he said, adding scientists need to get a better sense of ice sheet dynamics before they can offer a more precise estimate of future sea level rise. “We really have a lot left to understand before we can do better.”

According to computer climate models, sea levels are expected to rise because water expands as it warms, and the melting of glaciers and ice sheets in Greenland and Antarctica will contribute to global sea levels. The U.N. Intergovernmental Panel on Climate Change gave what it called a conservative estimate in 2007 that the ocean could rise between 7 and 23 inches by 2100.