Daniel C Jones

The Geoid: New Gravity Map of the Earth Helps Us Understand the World's Climate

by , 04/04/11

ESA GOCE Satellite

When we’re told about newly released satellite images of our Earth, we imagine beautiful swathes of green and blue with the occasional white of swirling storm clouds or snow-topped mountain ranges. But rarely do we picture a multi-colored root vegetable. ‘Potato Earth’ is the name being given to the new images of the globe as created by the European Space Agency’s (ESA) incredibly sleek GOCE satellite. The new map, known as a ‘geoid,’ traces the varying degrees of influence that the pull of gravity from the mass of rock under our feet has on the earth’s surface with unrivaled precision.

GOCE Satellite ocean currents

After two years of low-flying orbit the GOCE satellite has returned images that give scientists access to the most accurate model of the geoid ever produced. Gravity is strongest in yellow areas and is weakest in blue areas.

According to the ESA the geoid represents the surface of “an ideal global ocean in the absence of tides and currents, shaped only by gravity.” It is a crucial reference for measuring ocean circulation, sea-level change and ice dynamics – all affected by climate change.

Gravity does so much more than simply keep our feet on the ground. It is fundamental to how the oceans distribute the heat from the sun around the globe and it plays an important role in the tectonic movements of the Earth’s crust. The GOCE images can help us better understand what’s going on deep within the Earth when huge earthquakes – like the one that hit Japan last month – strike by giving us a 3D view of the forces at work beneath our feet.

The differences in the Earth’s gravitational signals are incredibly weak so in the GOCE geoid they have been magnified 10,000 times. But this does nothing to lessen the scale of the impact this can have on us in day-to-day life. For example, a boat off the coast of Europe (shown in bright yellow) can sit 180m “higher” than a boat in the middle of the Indian Ocean (show in deep blue) and still be on the same level plane.

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