June 2025

June 2025 | Oceanography

PERSPECTIVE

The National Academies Consensus Study Report, Potential

Hydrodynamic Impacts of Offshore Wind Energy on Nantucket

Shoals Regional Ecology: An Evaluation from Wind to Whales

(NASEM, 2024), is important, timely, and succinct. During this

time of political and financial uncertainty regarding the devel­

opment of offshore wind, this report, summarized by Hofmann

et al. (2025, in this issue), offers clear directions for the research

needed to resolve significant scientific and engineering questions

during a time of rapid change in the Northwest Atlantic Ocean.

The report highlights the difficulty of unraveling the impacts

of offshore wind development from oceanographic variabil­

ity. The Northwest Atlantic is one of the most rapidly warm­

ing regions in the world ocean (e.g., Pershing et al., 2015; Chen

et al., 2020; Seidov et al., 2021), resulting in a trend of increas­

ing stratification in the region (Harden et  al., 2020). While

there is a longer-term warming trend, in part relating to vari­

ability upstream (e.g.,  Gonçalves Neto et  al., 2021), extreme

events, such as marine heatwaves in the region, have resulted

in large temperature anomalies over time periods from days

to months. Further complicating the matter, the spatial scales

of the marine heatwaves depend on whether they result from

atmospheric forcing or ocean advection (e.g., Chen et al., 2014;

Großelindemann et al., 2022).

Another factor that makes attributing impacts in the region

complex is the manner in which Gulf Stream variability has influ­

enced continental shelf stratification and water mass properties

via increases in shelf break exchange processes. Gulf Stream

meanders have increased in peak-to-trough size, and their first

downstream appearance from the Cape Hatteras destabilization

point first shifted west over an extended period of time (Andres,

2016) and then shifted eastward over the last several years

(Sánchez-Roman et al., 2024). This increased Gulf Stream vari­

ability is likely related to a regime shift in the annual formation

rate of warm core rings in the year 2000 (Gangopadhyay et al.,

2019). An indication of the growing influence of Gulf Stream

rings and water masses on the continental shelf in this region

is the remarkable increase in frequency of mid-depth salinity

maximum intrusions (Gawarkiewicz et al., 2022). These intru­

sions commonly occur in proximity to warm core rings (Silver

et al., 2023) and bring warm salty water tens of kilometers shore­

ward of the shelf break and potentially into the offshore wind

lease areas off Nantucket Shoals. Significantly for northern right

whale prey fields, salinity profiles reveal there may be several dif­

ferent intrusions at different depths in the water column over the

continental shelf, thus possibly diminishing the concentration

within an individual intrusion layer.

The flow around offshore wind turbines is affected by pre-​

existing continental shelf processes and in turn alters those pro­

cesses. A key contribution of the Consensus Study Report is to

clearly delineate the three major scales over which the effects

on hydrodynamics must be considered and assessed: the indi­

vidual turbine scale, the wind farm scale including all turbines

in the region, and the larger regional scale over which the wind

farm scale exerts an impact via advection and changes in stratifi­

cation. This delineation is important as both the computational

approaches and the observational tools differ among the differ­

ent spatial scales. Prioritization is important, as is the linkage in

understanding among the scales.

A key portion of the report is the careful evaluation and sum­

mary of numerical modeling studies that highlight the wide

uncertainties regarding the impacts of turbine wakes on strati­

fication. Most of these studies have been directed toward infra­

structure in the North Sea, which exhibits considerable dif­

ferences in stratification, tidal velocities, and wind forcing

relative to the Nantucket Shoals region. Validation of mod­

els with careful observations is stressed and will be crucial to

reducing uncertainties.

Several challenges inhibit progress over these three spatial

scales. Large Eddy Simulations are needed at the individual tur­

bine scale to parameterize mixing and the downstream evo­

lution of turbulent wakes from the turbines. On larger scales,

much of the small-scale turbulence will need to be parameter­

ized. Progress in this specific area has been achieved by numer­

ical modelers in Europe, and parallel efforts are needed for the

Nantucket Shoals region.

A significant gap that is not addressed directly in the report is

the manner in which internal waves and tides have been chang­

ing over the past decade as stratification has changed. In addition

SETTING A COURSE

FOR RESEARCH ON OFFSHORE WIND DEVELOPMENT

IMPACTS NEAR NANTUCKET SHOALS

By Glen Gawarkiewicz