Offshore Wind Turbines Make Sediment Plumes in North Sea

offshore-wind-turbines-making-wakes

Offshore wind turbines installed in the North Sea have been giving rise to sediment plumes, satellite images taken by NASA’s Operational Land Imager (OLI) show.

For at least the past decade, satellites have spotted white dots cropping up in the North Sea. If viewed from Earth’s surface, you would see that these dots are actually wind turbines—huge arrays of towers rising from the sea and topped with electricity-generating rotors. But they’re doing more than harvesting the wind, NASA said.

Some of the North Sea’s most expansive arrays are visible in these images, acquired on 30 Jun, 2015, with the OLI on the Landsat 8 satellite.

When these images were acquired, there were 84 offshore wind farms in Europe, including some under construction. The North Sea accounts for the most offshore wind capacity—69 percent—in European seas, followed by the Irish Sea and Baltic Sea.

The turbines were built to take advantage of high winds blowing over the North Sea’s surface.

offshore-wind-turbines-making-wakes1
London Array OWF.

The 630MW London Array, visible in the first detailed image, spans 100 square kilometers. The wind farm, which first became operational in 2013, sits on two natural sandbanks in water as deep as 25 meters. The site was chosen because of its proximity to onshore electric power infrastructure and because it is beyond the main shipping lanes through the area.

Other significant wind farms, Thanet and the northern half of Greater Gabbard, are shown in the second and third detailed images.

Thanet OWF
Thanet OWF

Thanet spans 35 square kilometers and sits in water measuring 20 to 25 meters deep.

The entirety of Greater Gabbard spans 147 square kilometers and sits in water 24 to 34 meters deep.

Greater Gabbard OWF
Greater Gabbard OWF

The detailed views reveal light-brown plumes of suspended sediments extending from each tower. In a 2014 paper, researchers analyzed satellite imagery and found that the wakes, and plumes, can measure anywhere from 30 to 150 meters wide and up to several kilometers long. They are generally aligned with the direction of the tidal current.

It is not yet clear how this increased amount of suspended sediment could affect the relatively shallow underwater environment, which is known to be an important fish nursery, NASA said.

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