Ice Loss and Gravity Dips

GOCE orbit is so low that it experiences drag from the outer edges of Earth's atmosphere. The satellite's streamline structure and use of electric propulsion system counteract atmospheric drag to ensure that the data are of true gravity. Credit: ESA /AOES Medialab

GOCE orbit is so low that it experiences drag from the outer edges of Earth’s atmosphere. The satellite’s streamline structure and use of electric propulsion system counteract atmospheric drag to ensure that the data are of true gravity. Credit: ESA /AOES Medialab

Data from an Earth-observing satellite has provided unexpected evidence that ice loss in Antarctica has had a noticeable effect on Earth’s gravity.

The European Space Agency’s Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) launched in March of 2009 and was intended to orbit the Earth for 20 months. Instead, the spacecraft lasted 55 months, and completed its journey by re-entering Earth’s atmosphere in November 2013.

In 2001, GOCE delivered a model of the 'geoid' (Earth's gravity field) pictured here. At the time, it was the most accurate ever produced. The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue shades represent low values and the reds/yellows represent high values. Credit: ESA/HPF/DLR

In 2001, GOCE delivered a model of the ‘geoid’ (Earth’s gravity field) pictured here. At the time, it was the most accurate ever produced. The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue shades represent low values and the reds/yellows represent high values. Credit: ESA/HPF/DLR

The mission was designed to map Earth’s gravity field, and provided the most accurate gravity model of our planet to date. Gravity at the Earth’s surface varies slightly due to the planet’s rotation and the position of features like mountains and ocean trenches.

Models produced from GOCE data are used to study numerous aspects of our planet, including ocean circulation and changes in sea level. Using the models, scientists can also gain insights into the interior workings of our planet.

GOCE data is invaluable for Earth scientists who study changes in Earth’s climate; but it is also useful for astrobiologists studying the Earth system as a whole in order to understand how our planet became habitable for life, and how habitability might change in the future. This work forms the basis for understanding how and where habitable worlds could develop beyond our solar system.



ESA’s Gravity field and steady-state Ocean Circulation Explorer (GOCE). Credit: ESA
 

GOCE was not designed to study how gravity changes over time, but by working with data from the satellite, scientists have shown how the loss of mass from glaciers in West Antarctica has left a noticeable signature in our planet’s gravity field. The measurements from GOCE provide much greater detail than previous measurements from missions like the NASA-German Grace satellite.

The European Space Agency has a wealth of materials available for students and educators, including handouts like 'Earth Explorers' (above). Click <a href="http://esamultimedia.esa.int/multimedia/publications/BR-314/" target="_blank">here</a> to learn more. Image Credit: ESA

The European Space Agency has a wealth of materials available for students and educators, including handouts like ‘Earth Explorers’ (above). Click here to learn more. Image Credit: ESA

GOCE data could also be used to validate measurements from other missions, including ESA’s Cryosat satellite, which has been measuring ice loss in Antarctica.

“We are now working in an interdisciplinary team to extend the analysis of GOCE’s data to all of Antarctica,” said Johannes Bouman, of the German Geodetic Research Institute, in a press release from ESA. “This will help us gain further comparison with results from CryoSat for an even more reliable picture of actual changes in ice mass.”

Using 200 million measurements collected by ESA’s CryoSat mission between January 2011 and January 2014, researchers from the Alfred Wegener Institute in Germany have discovered that the Antarctic ice sheet is shrinking in volume by 125 cubic kilometres a year. The study, which was published in a paper published on 20 August 2014 in the European Geosciences Union’s Cryosphere journal, also showed that Greenland is losing about 375 cubic kilometres a year. Credit: Helm et al., The Cryosphere, 2014

Using 200 million measurements collected by ESA’s CryoSat mission between January 2011 and January 2014, researchers from the Alfred Wegener Institute in Germany have discovered that the Antarctic ice sheet is shrinking in volume by 125 cubic kilometres a year. The study, which was published in a paper published on 20 August 2014 in the European Geosciences Union’s Cryosphere journal, also showed that Greenland is losing about 375 cubic kilometres a year. Credit: Helm et al., The Cryosphere, 2014

GOCE may have ended its mission in 2013, but scientists will study the data returned by the satellite for years to come to provide a greater understanding of the Earth system and environmental changes that our planet may face in the future.



The animation, based on measurements from ESA’s GOCE satellite and the NASA–German Grace mission, shows that ice lost from West Antarctica has caused a dip in Earth’s gravity. Credit: ESA/DGFI/Planetary visions
 

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