Avalonon Sea
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offshore wind is They will move farther and farther from shore as demand for renewable energy grows and new floating turbine technology enables deepwater extension.
However, for the first time large areas of the British continental shelf now open for development are ‘seasonally stratified’. David Attenborough has described these seasonal seas as some of the most biologically productive on the planet.
Although they cover only 7 percent of the ocean, it is estimated that they make up between 10 and 30 percent of life at the bottom of the food web.
According to our new research, a by-product of deep-sea wind power is that the foundations of these floating turbines could help reverse the damaging effects of climate change on such seas.
In seasonally stratified seas, the water is completely mixed in winter but separates in layers in spring, with warm, sunlit water forming over the colder water below. The formation of this “stratification” in spring triggers a massive explosion of marine life as phytoplankton (microscopic algae) flourish in the warm surface waters, forming the base of a food chain that ultimately feeds fish, seabirds and whales.
However, the nutrients in the sunlit top layer are quickly depleted by the plankton bloom. After this point, growth depends on nutrients being stirred up from deep water by turbulence associated with tides, winds, and waves.
This turbulence not only stirs up nutrients, but also oxygen into the dark, deeper layers where dead plants and animals sink and rot. Since oxygen is required for decomposition, this mixture helps this “sea snow” to decompose and converts it back into useful nutrients.
Climate change could starve our shelf seas
Our changing climate means stratification begins earlier in the year and plankton blooms earlier in spring, out of sync with the life cycles of larger animals. Stratification is expected to increase in summer, a change already well documented in the open ocean.
Increasing stratification reduces the ability of natural turbulence to churn vital nutrients from the deep into the warm surface layer of water, thus reducing their ability to sustain marine ecosystems.
As the ocean warms, it also becomes less able to hold oxygen, potentially leading to poor water quality.
Where do wind farms come into play? The introduction of wind turbines into deeper water where the ocean is stratified will provide a new, artificial source of turbulence.
Water flowing past the floating turbine foundations creates eddies, causing the warm and cold layers to mix. In fact, we recently published research showing that wake of foundations at least doubles the natural turbulent mixing in the area of an offshore wind farm.
This increased turbulence could potentially offset climate change effects on stratification, increasing nutrient supply to the surface layer and oxygenation to deep water. Something similar is already happening on underwater banks, which is why places like Dogger Bank in the North Sea or the Grand Banks of Newfoundland are often home to very productive fisheries – shallow areas where different sea layers have mixed.
It appears that offshore wind could help seasonally stratified seas become more productive, biodiverse, and support more fish. Careful turbine design and wind farm planning could therefore be an important tool in the fight to save these important ecosystems from the worst effects of climate change.
This article was originally published on The conversation through BenLincoln and Tom Rippeth at University of Bangor and Robert Dorrell at the University of Hull. Read the original article here.
