Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Satellites reveal a mystery of large change in earth’s gravity field

02.08.2002


Satellite data since 1998 indicates the bulge in the Earth’s gravity field at the equator is growing, and scientists think that the ocean may hold the answer to the mystery of how the changes in the trend of Earth’s gravity are occurring.



Before 1998, Earth’s equatorial bulge in the gravity field was getting smaller because of the post-glacial rebound, or PGR, that occurred as a result of the melting of the ice sheets after the last Ice Age. When the ice sheets melted, land that was underneath the ice started rising. As the ground rebounded in this fashion, the gravity field changed.

"The Earth behaved much like putting your finger into a sponge ball and watching it slowly bounce back," said Christopher Cox, a research scientist supporting the Space Geodesy Branch at NASA’s Goddard Space Flight Center, Greenbelt, Md.


Currently, the Earth has a significant upward bulge at the equator, and a downward bulge at the poles. "Observations of the Earth’s gravity field show that some phenomena are counteracting the gravitational effects of PGR. Whereas PGR has been decreasing the bulge in the Earth’s gravity field at the equator, this recent phenomena is causing the bulge to increase," Cox said. Such changes in the gravity field can be sensed using ultra precise laser tracking of satellites to observe tiny changes in the orbits of those satellites and by tracking changes in the length of day or rotation of the Earth.

Scientists believe movements of mass cause this recent change from the high latitudes to the equator. Such large changes may be caused by climate change, but could also be part of normal long-period climatic variation. "The three areas that can trigger large changes in the Earth’s gravitational field are oceans, polar and glacial ice, and atmosphere," Cox said.

Cox and colleague Dr. Benjamin Chao have ruled out the atmosphere as the cause. Instead, they suggest a significant amount of Ice or water must be moving from high latitude regions to the equator, and oceans could be the vehicles of this movement.

Estimates of today’s glacier and polar ice melting are too small to explain the recent changes in the gravity field. If melting ice were the cause of the recent changes in the gravitational field, it would require melting a block of ice 10 km (6.2 miles) on each side by 5 km (3.1 miles) high every year since 1997 and pouring it into the oceans.

"The recent reports of large icebergs calving in Antarctica can’t explain this, because they were already floating in the ocean," Cox said.

Further, radar altimeter observations of the average sea level rise provided by the TOPEX/POSEIDON satellite show no corresponding change in the rate of the global sea level increase.

Consequently mass must have been redistributed within the oceans. That’s where the ocean circulation theory comes in. Ocean currents can redistribute mass quickly, such as the 5-year time frame that these changes were first observed. The TOPEX/POSEIDON observations of sea level height do show an increase in the equatorial bulge of the oceans corresponding to the observed gravity changes, but the data are not yet conclusive. One critical factor is the temperature of the world’s oceans, and its salinity, for which detailed data are not yet available.

In 2002 NASA also launched the GRACE and JASON missions, missions that will help to more precisely track these sorts of changes in Earth’s geodesy, and will launch the ICESAT mission this winter.

Lynn Chandler | EurekAlert!
Further information:
http://www.gsfc.nasa.gov/topstory/20020801gravityfield.html
http://ilrs.gsfc.nasa.gov
http://sealevel.jpl.nasa.gov/mission/mission.html

More articles from Earth Sciences:

nachricht World’s oldest known oxygen oasis discovered
18.01.2018 | Eberhard Karls Universität Tübingen

nachricht A close-up look at an uncommon underwater eruption
11.01.2018 | Woods Hole Oceanographic Institution

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

Method uses DNA, nanoparticles and lithography to make optically active structures

19.01.2018 | Materials Sciences

More genes are active in high-performance maize

19.01.2018 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>