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From: NASA Jet Propulsion Laboratory <info@jpl.nasa.gov>_______________________________________________
Date: July 7, 2005 7:59:49 PM EDT
To: Aaron Titus <titus@mailaps.org>
Subject: NASA Satellites Measure And Monitor Sea Level
Reply-To: info@jpl.nasa.gov
Alan Buis (818) 354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Dolores Beasley/Marta Metelko (202) 358-1753/1642
NASA Headquarters, Washington, D.C.
News Release: 2005-111 July 7, 2005
NASA Satellites Measure And Monitor Sea Level
For the first time, NASA has the tools and expertise to understand
the rate at which sea level is
changing, some of the mechanisms that drive those changes and the
effects that sea level change may
have worldwide.
"It's estimated that more than 100 million lives are potentially
impacted by a one-meter (3.3-foot)
increase in sea level," said Dr. Waleed Abdalati, head of the
Cryospheric Sciences Branch at NASA's
Goddard Space Flight Center, Greenbelt, Md. "When you consider
this information, the importance
of learning how and why these changes are occurring becomes clear,"
he added.
Although scientists have directly measured sea level since the
early part of the 20th century, it was not
known how many of the observed changes in sea level were real and
how many were related to
upward or downward movement of the land. Now satellites have
changed that by providing a
reference by which changes in ocean height can be determined
regardless of what the nearby land is
doing. With new satellite measurements, scientists are able to
better predict the rate at which sea
level is rising and the cause of that rise.
"In the last 50 years sea level has risen at an estimated rate of .
18 centimeters (.07 inches) per year,
but in the last 12 years that rate appears to be 3 centimeters (.12
inches) per year. Roughly half of
that is attributed to the expansion of ocean water as it has
increased in temperature, with the rest
coming from other sources," said Dr. Steve Nerem, associate
professor, Colorado Center for
Astrodynamics Research, University of Colorado, Boulder.
Another source of sea level rise is the increase in ice melting.
Evidence shows that sea levels rise and
fall as ice on land grows and shrinks. With the new measurements
now available, it's possible to
determine the rate at which ice is growing and shrinking.
"We've found the largest likely factor for sea level rise is
changes in the amount of ice that covers the
Earth. Three-fourths of the planet's freshwater is stored in
glaciers and ice sheets or the equivalent of
about 67 meters (220 feet) of sea level," said Dr. Eric Rignot,
principal scientist for the Radar Science
and Engineering Section at NASA's Jet Propulsion Laboratory,
Pasadena, Calif. "Ice cover is
shrinking much faster than we thought, with over half of recent sea
level rise due to the melting of ice
from Greenland, West Antarctica's Amundsen Sea and mountain
glaciers," he said.
Additionally, NASA scientists and partner researchers now are able
to measure and monitor the
world's waters globally in a sustained and comprehensive way using
a combination of satellite
observations and sensors in the ocean. By integrating the newly
available satellite and surface data,
scientists are better able to determine the causes and significance
of current sea level changes.
"Now the challenge is to develop an even deeper understanding of
what is responsible for sea level
rise and to monitor for possible future changes. That's where
NASA's satellites come in, with global
coverage and ability to examine the many factors involved," said
Dr. Laury Miller, chief of the
National Oceanic and Atmospheric Administration Laboratory for
Satellite Altimetry, Washington,
D.C.
NASA works with agency partners such as the National Oceanic and
Atmospheric Administration
and the National Science Foundation to explore and understand sea
level change. Critical resources
that NASA brings to bear on this issue include such satellites as:
-- Topex/Poseidon and Jason, the U.S. portions of which are managed
by JPL, which use radar to
map the precise features of the oceans' surface, measuring
ocean height and monitoring ocean
circulation;
-- Ice, Cloud and Land Elevation Satellite (IceSat), which studies
the mass of polar ice
sheets and their contributions to global sea level change;
-- Gravity Recovery And Climate Experiment (Grace), also managed by
JPL, which maps Earth's
gravitational field, allowing us to better understand movement
of water throughout the Earth.
For more information about sea level change on the Internet, visit:
http://www.nasa.gov/vision/earth/environment/
sealevel_scienceupdate.html .
For information about Topex/Poseidon and Jason on the Internet, visit:
http://sealevel.jpl.nasa.gov/ .
For information about Grace on the Internet, visit:
http://www.csr.utexas.edu/grace/ .
For information about NASA and agency programs on the Internet, visit:
http://www.nasa.gov/home/index.html .
JPL is managed for NASA by the California Institute of Technology
in Pasadena.
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