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.