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 First research results on the "spectacular meteorite fall" of Flensburg
18.02.2020 | Westfälische Wilhelms-Universität Münster

nachricht The Antarctica Factor: model uncertainties reveal upcoming sea-level risk
14.02.2020 | Potsdam-Institut für Klimafolgenforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

Im Focus: New synthesis methods enhance 3D chemical space for drug discovery

After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.

"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

"Make two out of one" - Division of Artificial Cells

19.02.2020 | Life Sciences

High-Performance Computing Center of the University of Stuttgart Receives new Supercomuter "Hawk"

19.02.2020 | Information Technology

A step towards controlling spin-dependent petahertz electronics by material defects

19.02.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>