Sea Level Rise Found to be Accelerating
- View SourceJuly 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 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
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 fifty years sea level has risen at an estimated rate of .07
of an inch per year, but in the last 12 years that rate appears to be .12
of an inch 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 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 (NOAA)
Laboratory for Satellite Altimetry, Washington.
NASA works with agency partners such as NOAA 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:
Ocean TOPography Experiment (TOPEX/Poseidon), which uses radar to map the
precise features of the oceans� surface;
Jason, which measures ocean height and monitors 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), 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:
Dolores Beasley/Marta Metelko
Goddard Space Flight Center, Greenbelt, Md.