Offshore Wind Power Could Alter Ocean Currents

Nov. 12, 2008 -- Generating wind power at sea may disturb ocean currents and marine ecosystems, according to a new study.

Offshore wind farms are common in Europe; Denmark, The Netherlands, and the United Kingdom all have several active installations. Wind power in the United States is currently confined to dry land, but three installations are planned off the coast of New Jersey, Rhode Island, and Delaware, totaling about 1,500 megawatts of generating capacity.

Extracting energy from wind changes regional air currents, which can in turn affect how the nearby ocean circulates, according to Goran Brostrom of the Norwegian Meteorological Institute in Oslo.

In a paper published this month in Journal of Marine Systems, Brostrom shows in a model that winds swirling at five to 10 meters per second (11 to 22 miles per hour) downwind of large farms are uneven. As they blow over the ocean they can roil the waters, causing upwelling.

The change in currents seems small -- a nudge of just one meter (3.3 feet) per day -- and the wind farms have to be around five square kilometers (1.9 square miles), which only the biggest do. But Brostrom said the effect is enough to bring nutrient-rich waters up from the depths, which marine life can thrive on.

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"I think you will see a large effect over time," he said. "You will get more plankton blooming, and you will see more vibrant life overall at that place."

Plankton blooms are infamous for causing toxic red tide and for sucking oxygen out of the water. But they can also be food sources for larger animals.

"Whether or not this is a good thing is a matter of debate," Brostrom said. Though he stressed that the goal for any man-made object should be to minimize environmental impact, he added: "I'm an optimist; I think this could be beneficial to local fisheries."