At a Glance:

Narragansett Bay is classified as a “tidal estuary”, and tides and the currents that result from them represent most of what transports material in Rhode Island Sound and over the continental shelf in our region as well.  Our tides are comparatively big because of the specific shape and size and depth of the ocean seafloor (“bathymetry”) and the orbit of the Earth and Moon. An interesting and complex set of currents flows around and through the Elizabeth Islands from Martha’s Vineyard and Woods Hole into our region.  It would take much more than adding a wind farm to affect these tides–perhaps an ice age or removal of an entire island!  To be efficient and to allow navigation between them, wind turbines are widely spaced and this means that a wind farm only reduces winds by a few percent in its wake.

A Deeper Dive:

After tides, winds, rivers and offshore variability such as Gulf Stream meanders can affect our region (https://fox-kemper.com/pubs/pdfs/SaneFox-Kemper23.pdf).  However, these phenomena and the currents of the mid-Atlantic Bight constantly vary due to seasons, weather, and climate (e.g., https://doi.org/10.5670/oceanog.2008.08).  These variations change the winds, temperature, and ocean stratification by double-digit percentages.  Wind farms, on the other hand, tend to extract much less energy from the winds than is caused by this variability (a 2-10% wind reduction directly in the wake of a wind farm is estimated from satellites https://earth.esa.int/eogateway/news/long-term-satellite-data-show-wind-farms-can-affect-local-air-currents).

Take the Revolution Wind project as an example.  It is a 704 megaWatt project spanning about 500 square kilometers of ocean.  The typical wind speed where revolution wind will be located is about 10 m/s, which works out to about 26,400 megaWatts of wind power flowing in the atmospheric boundary layer over the Revolution Wind region.  So, when Revolution Wind is operational at maximum capacity, it will convert only about 2% of the wind’s power to electricity.  Since the conversion isn’t perfect, we might expect a little more than 2% of the wind to be disrupted, consistent with the satellite estimates of the wake effects.  

Understanding Complexities:

Bigger currents, like the Gulf Stream, Kuroshio, or Antarctic Circumpolar Current, concentrate energy from the winds over vast oceanic regions.  The Gulf Stream is powered by the winds blowing over the whole midlatitude North Atlantic–roughly 8 million square kilometers compared to only the 500 square kilometers of Revolution Wind (i.e., roughly 0.006% of the area).  So, if Revolution Wind reduces winds by only 2% in 0.006% of the area, that amounts to only a one part in a million reduction in available wind power for the Gulf Stream.

More on ocean currents: https://education.nationalgeographic.org/resource/ocean-currents/

More on the resilience of the Gulf Stream: https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-9/#faq-9-3/#