Swarm satellite mission to try to sense ocean magnetism

European scientists are going to try to measure the movement of the oceans by tracing their magnetism alone.

The effort will be achieved using three super-sensitive spacecraft called Swarm, which should launch in 2012.

The magnetic signal of the tides sweeping around the globe has been seen before, but the new mission would aim to observe far more detail.

It should provide additional data on how the oceans transfer heat around the Earth, a key feature of the climate.

"When salty ocean water flows through the magnetic field of the Earth, an electric field is generated and this electric field again makes a magnetic field," explained Dr Hermann Lühr, from the German Research Centre for Geosciences (GFZ) and a leading investigator on Swarm.

"We hope to have the possibility to measure the ocean currents which are so important for climate dynamics, because oceans are transporting a lot of heat. The German Champ mission was the first to see at least the tidal signal, but with Swarm we want to be able to monitor the currents themselves."

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The Champ spacecraft came out of orbit just a few weeks ago, burning up in the Earth’s atmosphere.

Scientists reported first in 2003 that this satellite could sense the subtle magnetic field generated as the waters of the Earth moved under the gravitational tug of the Moon. This signal was apparent because of its very regular pattern.

Sensing the more complex signal from general ocean currents will be much more difficult, however.

Currently, researchers use a range of methods to track the currents, including altimetry - the measurement of ocean surface height. Data of magnetism in Earth’s rocks (GFZ) The global field is made up of several components, including the magnetism retained in crustal rocks

"All these different forms of measurement give you a different answer," said Dr Lühr.

"If you consider altimetry, this relies on seeing how the surface of the water is deformed by the current. But this can also be deformed by other effects like warming up, or having less salt in the water.

"However, if you look into the magnetic field this is just the integral motion from top to bottom of the water, and it will give you a really independent answer about the net transport of that water."

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