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Dec. 7, 2001

John Bluck

NASA Ames Research Center, Moffett Field, Calif.

(Phone: 650/604-5026 or 604-9000)

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AGU Moscone Center press room, rm. 111, San Francisco, Calif.

(Phone: 415/905-1007, general AGU information during meetings)



Earthquake studies and how much carbon North America absorbs annually into its ecosystems are just two of many subjects that Earth scientists from NASA Ames Research Center will present during the annual fall meeting of the American Geophysical Union (AGU) Dec. 10 -14 at San Francisco's Moscone Convention Center.

At least 40 scientists from NASA Ames, located in California's Silicon Valley, will take part in a wide range of Earth science presentations. In addition, an Ames researcher will receive the James B. Macelwane Medal that recognizes significant contributions to geophysical sciences by an outstanding young scientist.

"Our research using satellite data at NASA Ames shows that ecosystems in North America have been fairly consistent carbon sinks over the past 15 years, absorbing approximately one-fourth of the carbon dioxide emitted annually from burning fossil fuels in the United States," said Christopher Potter, a research scientist at NASA Ames. A carbon sink is an area where the rate of carbon uptake by living organisms exceeds the rate of carbon release, so that carbon is sequestered for longer than one year. "The exceptions to a North American sink have been years when climate warming was minimal, and we had a relatively cool year on the continent," he added.

Potter is one of four researchers who will discuss variations in the amount of carbon absorbed periodically by North American ecosystems. Together with his colleagues he will present comments about carbon sinks during a news conference on Thursday, Dec. 13 at 2 p.m. PST in room 112, Moscone Center. The scientists also will cover the uncertainties in measuring carbon sinks.

Potter also will co-chair a session, 'The North American Carbon Sink as a Case Study,' on Friday, Dec. 14 at 3:30 p.m. PST in Moscone Center room 122. He and colleagues will make an oral presentation in the same room at 4 p.m., "The North America Carbon Sink from 1982-1998 using Moderate-Resolution Imaging Spectrometer (MODIS) Algorithm Products." MODIS is on the Terra satellite, which was launched in 1999 (see MODIS images are used to produce maps of the state and activity of terrestrial vegetation. Potter's co-presenters include Steven Klooster of California State University Monterey Bay, Seaside, Calif.; and R. Myneni, Boston University, Boston.

In addition, Potter, Myneni, Klooster and NASA Ames scientist David Bubenheim will display a poster presentation with first-time estimates of the supply of acetone to the atmosphere from terrestrial sources that include living plant canopies, oxidation of dead plant matter, and harvesting of cultivated plants. Acetone is a volatile carbon compound that can act to 'cleanse' air in the lower atmosphere from a high level of polluting reactions. The session is slated for Friday, Dec. 14 at 8:30 a.m. PST in Hall D of the Moscone Center.

Ames scientist Azadeh Tabazadeh will receive the Macelwane medal, which recognizes significant contributions to geophysics by an outstanding young scientist. The AGU ceremony during which Tabazadeh will be honored begins at 5:30 p.m. PST on Dec. 12 in the San Francisco Marriott Hotel's Yerba Buena Ballroom, Salon 7. The Macelwane Medal, when awarded to a member, carries with it automatic designation as an AGU Fellow. Selection as a Fellow of AGU is an honor bestowed on only one tenth of 1 percent of the membership in any given year.

"Azadeh Tabazadeh is noted for her many applications of physical chemistry to problems of importance in atmospheric science," said Brain Toon of the University of Colorado, Boulder. "She initially explored the role of volcanic eruptions in injecting chlorine compounds into the stratosphere. . . Azadeh showed that the chlorine would be removed by precipitation in the moist rising volcanic column before it could enter the stratosphere. This paper ended 20 years of debate about this subject through its thorough analysis and plausibility," Toon explained.

Large volcanoes emit much more chlorine than all human-made chlorine emissions, but because volcanic chlorine compounds are precipitated, they do not deplete the ozone layer substantially, according to Tabazadeh. She also made significant contributions in the study of polar stratospheric clouds that are responsible for the formation of the Antarctic ozone hole, according to Toon.

A few days' of warning before some large earthquakes may someday be possible because the Earth emits signals before the ground shakes, according to Friedemann Freund, a scientist who works at NASA Ames. He will present his discoveries and theory on Wednesday, Dec. 12 at 1:30 p.m. PST in the seismology session to be held in Hall D, Moscone Center.

Freund has been investigating how rocks respond to stress. "If the stress level is high, electronic charges appear that momentarily turn the insulating rock into a semiconductor," he said. Semiconductors are materials that have a level of electrical conductivity between that of a metal and an insulator. When charges flow, they constitute an electric current. When there is an electric current, there also is a magnetic field. If current varies with time, electromagnetic waves will be emitted.

"The frequency of these electromagnetic waves will probably be very low, much lower than radio waves, but basically of the same nature," said Freund. "Scientists can pick them at the Earth’s surface with suitable antennas or by measuring the magnetic field pulses that go with them."

"It is much too early and, in fact, unwise to expect that earthquakes would soon become predictable beyond the statistical probability that is currently the state-of-the-art." Freund said. "But one day, we’ll learn to read the signals that the restless Earth emits before the rocks rupture with deadly force."

Ames scientist Jennifer L. Dungan will present a poster in a session highlighting analysis of results from NASA's MODIS instrument on the Terra satellite. Dungan's work is to test the accuracy of a computer model that predicts how much carbon ecosystems absorb. The study covers forests at several sites in North America, including central Massachusetts, eastern Wisconsin and central Tennessee for the 2001 growing season. Dungan's collaborator is Barry Ganapol, University of Arizona, Tucson, Ariz.

AGU fall meeting details are on the Internet at:

Journalists may search the AGU website ( ) for more details about Ames' AGU participation. Use the keyword '' or the researcher's e-mail address to locate abstracts and session information. To arrange interviews at AGU, reporters may contact Harvey Leifert in the AGU Press Room, MC 111, 415/905-1007. Journalists also can arrange interviews at AGU by using the message board located outside Moscone’s main exhibition hall.



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