Ocean Circulation Studies and Global Warming

Radioactive dating of the oceans by AMS is helping researchers understand ocean circulation patterns. Carbon-14 atoms, produced in the upper atmosphere when cosmic rays strike nitrogen nuclei, join with oxygen atoms to form carbon dioxide (CO₂). The atmosphere exchanges CO₂ with the ocean, which tends to inhale CO₂ near the poles and to exhale it near the equator. As seawater ages, the carbon-14 content of its CO₂ decreases. Researchers are creating a 3-dimensional map of the age of the oceans based on AMS studies of seawater samples taken at various depths, latitudes, and longitudes. These studies are helping researchers to understand the oceans' large-scale circulation patters and the earth's weather patterns.

Many people are concerned that man-made CO2 contributes to global warming. Since the atmosphere exchanges CO2 with the ocean, the 3-dimensional map of oceanic carbon-14 is also helping researchers learn about the natural fluctuations of the earth's CO2 cycle -- an essential step toward understanding the significance of man-made CO2 in the atmosphere Water Resources The National Park Service asked hydrologists to evaluate water supply alternatives in the Wawona area of Yosemite National Park. In cooperation with physicists and nuclear geochemists, the hydrologists found that the ground water in Wawona's fractured granitic rocks is vertically segregated.

Sampling Seawater Woods Hole Oceanographic Institute

Wawona Basin Yosemite National Park

AMS measurements of carbon-14 showed that rainfall recently recharged the shallow ground water. But the deeper zone of the aquifer contains a mixture of water from a deep saline source and water from ancient rainfall; it was last recharged about 6,000 years ago. The deep and shallow zones are not hydraulically connected. Since the deep zone recharges slowly, the scientists recommended high altitude springs as a more reliable source of water for Wawona than deep wells.

Air Quality

Since wood contains carbon-14 and fossil fuels do not, AMS studies of particulates in smog can identify the relative contributions of wood burning and fossil fuel burning. These studies have shown that wood burning is the major source of air pollution during winters in Albuquerque and Las Vegas.

Nuclear physicists are studying air pollution in the National Parks by proton-induced X-ray emission (PIXE). Since PIXE can detect constituents of the haze in concentrations below 1 part per trillion, the physicists can often identify the source of the pollution. They identified the Navajo Generating Station, a coal-fired power plant, as the main source of air pollution in the Grand Canyon. Their data convinced plant operators to install scrubbing equipment to reduce emissions by 90%.

Grand Canyon with Poor Air Quality
U.C. Davis

Grand Canyon, Same Spot with Good Air Quality
Aaron Glass Studios

Stratospheric Ozone Depletion

 

Man-made chlorofluorocarbons in the atmosphere have depleted the ozone layer over Antarctica. In the spring, half the ozone over the South Pole disappears, including nearly 100% of the ozone at altitudes between 10 and 20 kilometers. Since ozone screens the sun's ultraviolet rays, its depletion over populated areas could increase cancer rates. AMS studies of radioisotopes such as beryllium-7 and beryllium-10 are contributing to an understanding of ozone depletion. These beryllium isotopes are created in the stratosphere when cosmic rays strike nitrogen atoms. AMS researchers are studying the concentration of these isotopes in falling snow and in air samples collected by high-altitude aircraft. Since beryllium isotopes attach readily to aerosols, they are helping scientists to understand aerosol movement in the upper atmosphere. Aerosol particles serve as host sites for chemical reactions which create the forms of chlorine that destroy ozone.

Information provided by: http://www.phy.anl.gov