american geophysical union

Study Finds Space Shuttle Exhaust Creates Night-shining Clouds

Exhaust from the main engines of NASA’s space shuttle, which is about 97 percent water vapor, can travel to the Arctic in Earth’s thermosphere, the highest part of the atmosphere, where it forms ice to create clouds that shine at night, according to a new study. The thermosphere is above 88 kilometers [55 miles] altitude. The clouds settle to around 82 kilometers [51 miles] altitude in the layer directly below, called the mesosphere. The stratosphere and the troposphere lie in that order below the mesosphere.

Atmospheric Mercury Has Declined — But Why?

The amount of gaseous mercury in the atmosphere has dropped sharply from its peak in the 1980s and has remained relatively constant since the mid 1990s. This welcome decline may result from control measures undertaken in western Europe and North America, but scientists who have just concluded a study of atmospheric mercury say they cannot reconcile the amounts actually found with current understanding of natural and manmade sources of the element.

New Climate Model Predicts Greater 21st Century Warming

For the first time, scientists have incorporated multiple human and natural factors into a climate projection model. They predict that increased carbon dioxide in the atmosphere, due to changes in the carbon cycle, combined with a decrease in human-produced sulphates, may cause accelerated global warming during the 21st century, as compared with simulations without these feedback effects.

Should Memphis Build for California Style Earthquakes?

The federal government is urging Memphis and other parts of the Midwest to adopt a new building code that would make buildings as earthquake resistant as those in southern California, where shaking is much more likely to seriously damage a building. A new study by researchers at Northwestern University, the Reaves Firm in Memphis, and Los Alamos National Laboratory finds that the prescribed measures for the Midwest’s New Madrid seismic zone (NMSZ) would cost far more than the damage prevented. The New Madrid seismic zone includes parts of Tennessee, Kentucky, Missouri, Arkansas, Illinois, Indiana, and Mississippi.

Chinese Dust Found Atop French Alps

Dust from China’s Takla-Makan desert traveled more than 20,000 kilometers [12,000 miles] in about two weeks, crossing the Pacific Ocean, North America, and the Atlantic Ocean, before settling atop the French Alps. Chinese dust plumes had been known to reach North America and even Greenland, but had never before been reported in Europe.

Black Water Turns the Tide on Florida Coral

A patch of “black water”spanning over 100 kilometers [60 miles] in diameter formed off southwestern Florida in early 2002 and contributed to severe coral reef stress and death in the Florida Keys. The “black water” contained a high abundance of toxic and non-toxic microscopic plants. When scientists examined the data collected by divers from the dark water area in the Florida Keys, they discovered a 70 percent decrease in stony coral cover, a 40 percent reduction of coral species, and a near-elimination of sponge colonies at two reef sites after the dark water passed. By examining satellite images and field survey data, they concluded that the coral reef ecosystem was stressed by microscopic organisms and toxins contained in the dark water.

Job Market Remains Strong for Geoscience Graduates

Students who completed doctoral degrees in Earth and space sciences in 2001 entered a relatively strong job market, with most finding employment quickly with higher salaries, while remaining within their respective fields, according to a new report from the American Geophysical Union (AGU), American Geological Institute (AGI), and American Institute of Physics (AIP).

Scientists Find Geochemical Fingerprint of World Trade Center Collapse

Dust and debris deposits associated with the September 11, 2001, terrorist attack on the World Trade Center have left a distinct fingerprint on the sedimentary record in New York Harbor, scientists have found. Their results appear in the January 21, 2003, issue of the journal EOS, a publication of the American Geophysical Union. This geochemical fingerprint, the researchers believe, may facilitate a better understanding of the short-to-medium term processes that affect the input, dispersal, and fate of particles and contaminants in the lower Hudson River.

Surprises from Past Could Spell Longer Droughts, Rising Sea Levels

Abrupt climate changes could lead to decade-long droughts and massive sea-level rise, according to a University of Arizona geoscientist who studies the climate of the distant past. Factors that influence the climate system, such as natural changes in the Earth’s orbit or rising carbon dioxide emissions from cars and power plants, can result in dramatic climate shifts, says Jonathan Overpeck, a professor of geosciences and director of the UA Institute for the Study of Planet Earth. Scientists studying natural climate records, such as the variations in tree rings and gas bubbles trapped in the polar ice caps, find ample evidence of these types of rapid changes in the past — sometimes occurring in a decade or less.