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SCIENTISTS' SHOWDOWN WITH SOIL MOISTURE AT THE O.K CORAL 

by Gretchen Cook-Anderson and Sandy Miller Hays

Tombstone, Ariz., is a dusty place known for Wyatt Earp's famous 1881 "Shootout at the O.K. Corral." This year, from August 2 to 27, it will be known as the place where scientists from NASA, the U.S. Department of Agriculture (USDA), the National Oceanic and Atmospheric Administration (NOAA), and other institutions gather and study soil moisture to improve weather forecasts and the ability to interpret satellite data.

By identifying how much moisture is retained in soils, hydrologists will be able to determine how much more water can be absorbed, and thus better estimate the potential for flooding or how much water sinks into the water table. During July and August, the U.S. Southwestern monsoon season is characterized by a wind pattern shift that exerts a strong influence on precipitation and temperatures across the Western United States, Mexico and adjacent ocean areas. This change in winds over the region creates many rainy days and heavy rainfall, which are ideal conditions for studying soil moisture.

The study, called the Soil Moisture Experiment 2004, or SMEX04, will use ground teams, airplanes and NASA satellites and instruments to measure soil moisture in Tombstone, Ariz., and Sonora, Mexico, where water supplies are critical.

Researchers from NASA, USDA, NOAA, Sonora Research Institute and more than a dozen universities will be on the ground and in the air with advanced technology to get a better read on soil moisture. SMEX scientists also want to know what atmospheric conditions create long-lasting rainfalls over a large area. By knowing which factors create large or small rainfall, hydrologists can provide better forecasts and know how much water will be available to people.

"The Western U.S. relies on water from the Southwestern monsoon system to fill its aquifers. Accurate measurements of soil moisture will assist in better water supply forecasts associated with the monsoon in the water-scarce western U.S," said Tom Jackson, USDA Agricultural Research Service hydrologist and lead for SMEX.

From space, NASA's Aqua, Terra and QuikScat satellites will provide various measurements. Aqua's Advanced Microwave Scanning Radiometer (AMSR-E) instrument will measure soil moisture; Terra's Moderate Resolution Spectroradiometer (MODIS) will provide vegetation status; and Terra's Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) will measure the surface temperature. The SeaWinds instrument on the QuikScat satellite will observe the monsoon winds that bring in the moisture from the Pacific Ocean to the U.S. Southwest.

Closer to Earth, microwave radiometers on the Naval Research Laboratory P-3 aircraft and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) on NASA's ER-2 high-altitude aircraft will fly over the areas to measure soil moisture. AVIRIS will also help test new methods for remotely sensing water content in plants. Meanwhile, ground instruments will measure the temperature and percentage of moisture in soils from 2 to 40 inches deep. The satellite, airplane and ground data will be compared.

The SMEX04 mission adds to two prior SMEX experiments in 2002 and 2003, and is part of the larger North American Monsoon Experiment (NAME), led by NOAA, which is dedicated to understanding how the Southwestern U.S. monsoon season works. Monsoons need to be accurately understood and predicted by weather and climate models, because their influence on seasonal weather, including floods and droughts, can significantly disrupt regional economies and populations.

NASA's Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.  
End

   

photos>
Soil showdown
Soil showdown 1
 
Soil showdown 2
 
Soil showdown 3
 
Soil showdown 4
 
Soil showdown 5
 
http://www.gsfc.nasa.gov
Gretchen Cook-Anderson
Headquarters, Washington
(Phone: 202/358-0836)

Sandy Miller Hays
USDA Agricultural Research Service, Washington
(Phone: 301/504-1638)                                          
RELEASE : 04-250

RETREATING GLACIERS SPUR ALASKAN EARTHQUAKES

by Gretchen Cook-Anderson and Krishna Ramanujan  

In a new study, NASA and United States Geological Survey (USGS) scientists found that retreating glaciers in southern Alaska may be opening the way for future earthquakes.

The study examined the likelihood of increased earthquake activity in southern Alaska as a result of rapidly melting glaciers. As glaciers melt they lighten the load on the Earth's crust. Tectonic plates, that are mobile pieces of the Earth's crust, can then move more freely. The study appears in the July issue of the Journal of Global and Planetary Change.

Jeanne Sauber of NASA's Goddard Space Flight Center, Greenbelt, Md., and Bruce Molnia, a research geologist at USGS, Reston, Va., used NASA satellite and global positioning system receivers, as well as computer models, to study movements of Earth's plates and shrinking glaciers in the area.

"Historically, when big ice masses started to retreat, the number of earthquakes increased," Sauber said. "More than 10,000 years ago, at the end of the great ice age, big earthquakes occurred in Scandinavia as the large glaciers began to melt. In Canada, many more moderate earthquakes occurred as ice sheets melted there," she added.

Southern Alaskan glaciers are very sensitive to climate change, Sauber added. Many glaciers have shrunk or disappeared over the last 100 years. The trend, which appears to be accelerating, seems to be caused by higher temperatures and changes in precipitation.

In southern Alaska, a tectonic plate under the Pacific Ocean is pushing into the coast, which creates very steep mountains. The high mountains and heavy precipitation are critical for glacier formation. The colliding plates create a great deal of pressure that builds up, and eventually is relieved by earthquakes.

The weight of a large glacier on top of these active earthquake areas can help keep things stable. But, as the glaciers melt and their load on the plate lessens, there is a greater likelihood of an earthquake happening to relieve the large strain underneath.

Even though shrinking glaciers make it easier for earthquakes to occur, the forcing together of tectonic plates is the main reason behind major earthquakes.

The researchers believe that a 1979 earthquake in southern Alaska, called the St. Elias earthquake, was promoted by wasting glaciers in the area. The earthquake had a magnitude of 7.2 on the Richter scale.

Along the fault zone, in the region of the St. Elias earthquake, pressure from the Pacific plate sliding under the continental plate had built up since 1899 when previous earthquakes occurred. Between 1899 and 1979, many glaciers near the fault zone thinned by hundreds of meters and some completely disappeared. Photographs of these glaciers, many taken by Molnia during the last 30 years, were used to identify details within areas of greatest ice loss.

Field measurements were also used to determine how much the glacier's ice thickness changed since the late 19th century. The researchers estimated the volume of ice that melted and then calculated how much instability the loss of ice may have caused. They found the loss of ice would have been enough to stimulate the 1979 earthquake.

Along with global positioning system measurements made by Sauber and Molnia a number of NASA satellites were used to document glacier variability. Data from Landsat-7 and the Shuttle Radar Topography Mission (SRTM) were used to study glacier extent and topography. Currently, NASA's ICESat satellite is being used to measure how the glacier thicknesses are changing.

"In the future, in areas like Alaska where earthquakes occur and glaciers are changing, their relationship must be considered to better assess earthquake hazard, and our satellite assets are allowing us to do this by tracking the changes in extent and volume of the ice, and movement of the Earth," Sauber said.  End

photos and movies>
Glaciers Earthquakes
Glaciers Earthquakes 1
Click for animation showing a cumulative view of earthquake activity for the whole world from 1960 through 1995.
Glaciers Earthquakes 2
Click for animation of a flying tour through Glacier Bay National Park and Preserve in southern Alaska featuring Landsat imagery draped over elevation data
http://www.gsfc.nasa.gov

Gretchen Cook-Anderson                                  Headquarters, Washington                      (Phone: 202/358-0836)

Krishna Ramanujan                                            Goddard Space Flight Center, Greenbelt, Md. (Phone: 607/273-2561)                             RELEASE: 04-252

 
 
 
 
 
 
 

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