Sunday, December 3, 2017

Copernicus ocean currents

Major Global Ocean Currents at the surface (red) and bottom of the ocean (blue)
Our ocean currents are part of the most powerful machine on Earth.
Did you know?: 
Sea water is 832 times as dense as air,
providing a 5 knot ocean current with more kinetic energy than a 350 km/h wind. 
To learn more visit the CMEMS website

 Map of the Gulf Stream and Drift (Maury, 1858)

The Sea Level Thematic Center (SL TAC), part of the Copernicus Marine Service is in charge of providing satellite sea surface height and wave observation data.
“We then went with the current of the sea's greatest river, which has its own banks, fish, and temperature. I mean the Gulf Stream. It is indeed a river that runs independently through the middle of the Atlantic, its waters never mixing with the ocean's waters. It's a salty river, saltier than the sea surrounding it. Its average depth is 3,000 feet, its average width sixty miles. In certain localities its current moves at a speed of four kilometers per hour. The unchanging volume of its waters is greater than that of all the world's rivers combined.” (Jules Verne, 20,000 leagues under the sea)
Our vision of ocean currents is slightly more complex now than in 1869 when Jules Verne published his novel, but some of the above statement still remain true (it was mostly coming from the oceanographer Matthew Maury, who wrote « The Physical Oceanography of the Sea », published 1855).
The complexity lies in the turbulence: the ocean currents are not “straight” rivers crossing the seas as might be interpreted from the citation above, but turbulent flows shedding eddies all along their paths.
Their observation now is done not only at sea, but also from above: satellites enable to measure the reliefs of the sea surface.
These in turn can be used to compute the currents which are turning around the “hills” and “valleys” of this surface.
The steeper the slope of the relief, the faster the currents, so that we can map ocean currents any day of the last 25 years over the whole world from observations.
Over those 25 years, no less than 12 satellites has been used, with currently 6 of them measuring, enabling to make the most detailed daily maps of ocean surface ever.
Copernicus Marine Service is providing such measurements for use in science, forecasts and practical applications.

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