Twin-satellites GRACE with the earth’s gravity field. By GFZ, Astrium.

Gravity is climate – 10 years of climate research with GRACE twin satellites

By greenland today

01 APR 2012

The melting of glaciers in Greenland has now for ten years been measured with high accuracy from space, by the twin satellites GRACE (Gravity Recovery and Climate Experiment).
Gravity field measurements with satellite
The primary scientific goal of the GRACE satellite mission is to measure the gravitational field of the earth and its changes over time on a global scale with unprecedented accuracy. From the varying distance between the two satellites, scientists can determine the gravitational field of the earth. Approximately every 30 days, the satellite pair has collected enough data for a complete global map.
GRACE is a joint mission with the German Aerospace Center (DLR) and the German Research Center for Geosciences (GFZ), in partnership with the University of Texas at Austin.
Click <here> for more information on GRACE
Newton’s Laws
One of Newton’s laws states that the gravity of an object depends directly on its mass. So when the mass of the Greenland ice sheet changes, so does the gravity, and the GRACE gravity field measurements therefore give information on mass changes, including climate-related ones like snow and ice masses.
The potato planet
The uneven distribution of mass causes the earth to have an irregular shape, which deviates significantly from sphericity. This potato shape is equally subject to temporal changes. With GRACE, this adjustment can for the first time be accurately detected globally.
Measuring Greenland’s Changing Ice Mass
The Greenland ice shield had to cope with up to 240 gigatons of mass loss between 2002 and 2011. These statements were made possible by the high-precision measurements of the GRACE mission, whose data records result in a hitherto unequaled accurate picture of the earth’s gravity.
The Russel Glacier in Greenland. Photo Jason Box.
Anniversary in space
On 17 March 2012, the two GRACE twin satellites had been in orbit for exactly 10 years. GRACE twin satellites have circled the Earth more than 55 000 times on a near polar orbit at about 450 to 500 km altitude and a distance of 220 km, and continuously collected data.
Climate Models
This enabled the observation and analysis of climate-related processes from the monthly gravity field models over the last 10 years.
Some of the measurements with effect for Greenland
– The increase or decrease of the ice and snow masses
– The observation of surface
In the years 2003 to 2011, Greenland has been losing large amounts of water into the ocean as ice melts from its surface and glaciers discharge more and more ice into the sea.
Image credit: NASA/JPL-Caltech/University of Texas Center for Space
See animation <here>
Future measuring
GRACE are now running for twice as long as originally planned. An end of the mission is, still in sight. Theres already initiated a follow-up mission and from 2017 two GRACE-FO (follow-on) satellites will orbit around the Earth, provide reliable information on global trends in climate.
Sources : Helmholtz Association of German Research Centres, NASA, the German Research Center for Geosciences (GFZ), Wikipedia, Jet Propulsion Laboratory, California Institute of Technology,, German Aerospace Center (DLR), University of Texas at Austin.