The so-called ‘cold pool’, a unique oceanographic feature that lies along the eastern US seaboard from Massachusetts to North Carolina, is formed by strong seasonal “stratification traps” containing water under 10°C that support vast natural fisheries, including the most lucrative shellfish harvesting grounds in the US.

A new study from Rutger’s University pointed up that operating offshore wind farms might alter oceanographic processes that “establish, maintain, and degrade stratification associated with the cold pool through vertical mixing in this seasonally dynamic system”.

Changes in the stratification could have important consequences for how the cold pool works but little research has been done outside of Europe so far “to understand the interaction between offshore wind turbines and underlying ocean conditions,” note the researchers involved, not least “at scales ranging from individual turbines to entire wind farms” of gigawatt-plus capacity.

“These studies have examined turbulent mixing generated by turbine structure, wind extraction reducing surface wind stress and altering water column turbulence. These mechanisms could influence ocean mixing and in turn stratification that is a key characteristic of the cold pool,” said the authors of the study.

“The majority of research to date on offshore wind turbine effects on ocean mixing were carried out in, or simulated to represent, coastal waters around Northern Europe … where oceanographic conditions … differ in many important ways compared to that of the Mid Atlantic Bight.

“Generally, continental shelf waters in Northern Europe are less stratified seasonally and have stronger tidal currents and higher turbulence than those of the Mid Atlantic Bight. Thus, results from the European studies characterizing potential impacts of offshore wind facilities on stratification are more representative of impacts we might expect during the relatively weaker stratified time periods in spring and fall during cold pool ‘set up’ and ‘breakdown’.

During the highly stratified summer months, the researchers said, “previous results suggest it is less likely that the structures will induce mixing sufficient to overcome the strong stratification and impact cold pool integrity, nor the broad exchange between the surface and bottom water layers”.

“Nonetheless, the potential for these multiple wind energy arrays to alter oceanographic processes, and the biological systems that rely on them is possible.”

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