Chapter 2
Examples of Observational Needs

On the workshop’s first day, participants divided into breakout groups to consider oceanographic and atmospheric parameters relevant to resolving key physical and ecological questions. Data on these parameters, collected using appropriate and robust methods, can improve the overall understanding of how wind farms affect the ocean and its ecosystems. While there is existing instrumentation and research to inform some of these measurements, participants also discussed areas where more tools or knowledge may be needed to guide monitoring approaches.

The discussions centered around two scales: the single turbine scale and the WEA scale. However, many participants noted that effects could span both scales, especially with regard to the relationship between zooplankton aggregation and internal waves. The scales also blur when discussing turbulence, which is affected by upstream hydrodynamics and impacts turbine-area and downstream waters and is especially challenging to measure. This highlights the need to characterize the scale at which physical processes are influencing zooplankton.

Participants also considered the different timescales relevant to addressing questions about the impacts of wind energy developments. Many participants underscored the importance of both short- and long-term monitoring, including short-term monitoring for focused process studies along with long-term monitoring to access change. Consistent monitoring can provide an avenue for addressing issues as they occur; however, it was also noted that interannual variability is high in a system as dynamic as the ocean, and temporal comparisons may be unreliable for identifying impacts from wind installations.

BREAKOUT DISCUSSION HIGHLIGHTS: EXAMPLES OF OBSERVATIONAL NEEDS AT THE TURBINE SCALE

At the turbine scale, several participants stressed the importance of short-term process studies, ideally to collect data before turbine installation to create a baseline level of knowledge of wind and wake behavior in the area. These data can be

incorporated into large eddy simulation (LES) models to improve and constrain their output. After installation, some participants said that long-term monitoring is important to calculate impacts in the region, revise LES models, and extrapolate for WEA effects from multiple turbines.

Measuring Physical Parameters

A wide array of parameters could be measured as part of process studies to calculate impacts of offshore wind development in the region. Parameters include the length, width, vertical scale, and downstream distance of the ocean wake; turbulent kinetic energy (TKE); water temperature, salinity, and surface roughness; wave size; and effective flow around the turbine foundation. In addition, some participants suggested measuring buoyancy, the stratification profile, atmospheric stability, wind velocity, and wind shear, emphasizing that measurements could ideally be taken at multiple locations, including at turbine height (although exactly where on the turbine was not identified), at the sea surface near the turbine, at locations downstream from the turbine, at substations, and potentially at the ocean floor near a turbine. Measurements taken in the air above a turbine would not likely be useful.

All of these data could be extremely useful for validating and improving LES at the less-than-1-kilometer scale; in addition, some participants suggested these measurements could be revisited periodically to assess changes or be redone if new foundations are installed. However, many challenges to measuring these variables were explored. For example, TKE measurements are expensive, and challenging to generate even from land, and so variable that comparison may not be possible. In addition, a “wake” from a wind turbine is not one single thing but an amalgamation of multiple wakes that are constantly changing and are influenced by a complex array of factors, such as temperature, density, and ambient currents. How turbine foundations may alter wakes is not well understood, and wakes also merge as the scale widens from a single turbine to a WEA, making it important to consider timescales and cumulative effects.

Another challenge arises from the amount and frequency of data needed. Collecting short-term measurements of many complex parameters at the second and minute timescales over a period of weeks or months is daunting. Yet this is important to do because these variables change quickly and often because of tides, weather, seasonality, storms, freshwater intrusions, scour protection makeups, foundation growth, and other factors, none of which are included in current LES models. Some participants noted that, while laboratory experiments may be more feasible, they cannot effectively connect turbine effects to zooplankton aggregation.

In addition to intensive short-term monitoring efforts, long-term measurements taken in strategically chosen locations can be used to validate and improve LES models. While these measurements do not necessarily have to be continuous, it is ideal if they are regular enough to determine seasonality and capture some typical extreme events. Some participants also noted that measurements could be collected during wind turbine construction to understand the impacts of construction activities.

Certain factors may constrain how data may be accessed and used. For example, the location at which measurements are taken can influence how the data are interpreted, but information such as the height of a turbine may be proprietary. Some participants noted that this information is important to understand the transfer function between hub height and sea surface, which can be extrapolated for regional effects.

Given the challenges of collecting data for the wide variety of parameters identified at the different locations and temporal scales needed for robust models, obtaining relevant measurements will likely involve large amounts of funding, staff, and expertise. To make this more feasible, several participants suggested leveraging existing instrumentation and data collection systems wherever possible. For example, sea surface satellite data (a data source that has been useful in studying wind developments in the North Sea) could potentially be used to track sediment plumes, which could be used to model wakes. Some participants also suggested that operators of existing offshore arrays may be willing to share some proprietary data. While measurements from onshore wind turbines, which are different sizes from those used offshore, may not be directly useful, these data could offer some insights into which downstream changes are likely to be most impactful.

For water dynamics, data from acoustic Doppler current profilers (ADCPs), bottom-mounted profilers that move in and out of wakes to measure the currents, could be used for long-term observation of the area waters. In addition, thermistor strings are useful for measuring internal waves, and sensors have been developed for measuring many of the other variables identified. Some participants said that, ideally, sensors can be engineered into turbine foundation designs; if not, they can be affixed to the turbines themselves or float nearby. Open questions include how many sensors are needed and how close to the turbines they should be.

Understanding the Biology

There are many unanswered questions about zooplankton aggregation and whale behavior, even before turning to the question of whether the presence of wind turbines will affect these species and their interactions and the equally difficult question of whether and how that effect might be measured. For example, some participants pointed out that it is unknown exactly what factors may facilitate or inhibit zooplankton aggregations; how to best characterize and measure these aggregations; how turbulence affects zooplankton behavior; and what factors influence whales’ feeding patterns, including whether there are aggregation thresholds for attracting whales’ attention.

Based on the available evidence, scientists understand that the Gulf of Maine is the primary area supporting production of the Calanus finmarchicus aggregations found in Nantucket Shoals. There are currently no turbines in the Gulf of Maine, but there is a possibility that turbines in the areas through which zooplankton travel on their way to Nantucket Shoals could affect aggregation, the availability of nutrients, and other population dynamics in unknown ways. Baseline monitoring

of zooplankton productivity in the Gulf of Maine could provide insights to agencies, developers, and the state of Maine on potential future ecological impacts of offshore wind development in the region.

Measuring zooplankton aggregations at the turbine scale is a challenge. One option is to take measurements with acoustic surveys. These surveys have limitations, but they could be integrated with other data sources, such as data from video plankton recorders (VPRs), which can be deployed from fixed platforms or boats and can be used both upstream and downstream of turbines to better understand which species are present. In addition, it is important to complement acoustic surveys with net tows to confirm which species are contributing to the acoustic scattering. This physical data can also be used to inform lab experiments and models. In addition, bottom-mounted sensors may help map and measure plankton fields. While obtaining data from sites “guaranteed” to have zooplankton aggregations would be ideal, several participants posited that finding and measuring a proxy site to extrapolate or model potential aggregation effects is unlikely to be feasible given the variability and unpredictability of these aggregations.

Some participants also noted that Maxar satellites produce imagery at a very fine scale and could be used to map zooplankton patches occurring at the surface. Measuring the presence of nutrients and phytoplankton, which zooplankton feed upon, could be another promising approach. This could be done, for example, with moored submersible ultraviolet nitrate analyzers (although these require a power supply and frequent maintenance); a PlanktoScope; acoustic sampling; or chlorophyll tracers. Alternately, these data could be extrapolated from the Imaging FlowCytobot, which also provides data on phytoplankton species and size.

BREAKOUT DISCUSSION HIGHLIGHTS: EXAMPLES OF OBSERVATIONAL NEEDS AT THE WEA SCALE

Data from process studies can shed light on WEA-scale impacts when the measurements are reliable and appropriate for a larger scale. These data can also be compared with LES model output, and the studies can evolve into a long-term observational system that may be able to differentiate WEA effects from other factors. In addition, numerical models and computational fluid dynamics approaches can also be valuable for understanding effects at this larger scale, and these data can be incorporated into LES models. To widen the scope of LES models and better understand biological dynamics, some participants suggested that these models’ output can be triangulated with satellite visualizations of large internal waves that transport zooplankton. A larger question is whether a validated LES model from Nantucket Shoals data can be applied to other areas, which will have different conditions and species.

Measuring Physical Parameters

Parameters that are useful to measure for the WEA scale include surface roughness, rugosity, currents, turbulence, sea surface wind, wind abnormalities, and waves. Several participants also stressed the importance of measuring boundary layer dynamics, at the bottom and on the surface to understand the conditions upstream from a wind farm and its internal waves, which influence wakes, currents, and zooplankton advection. In addition to internal waves, solitons—nonlinear, self-reinforcing, localized wave packets—could create unexpected conditions at this scale. Some participants posited that waves are less important than wakes, although both are so variable that measuring them is challenging.

Some participants also suggested measuring and aggregating each turbine blade’s effects on turbulence. Stratification is especially important, and several participants suggested that useful data can be taken from moorings at multiple depths. However, since stratification changes seasonally and is greatly affected by wakes and downwinds, some participants noted that understanding the fluid mechanics involved is a complicated task.

Temperature and salinity are also critical variables to measure at the appropriate distance and depth, especially for understanding animal aggregation, and these factors also affect stratification. These parameters may be easier to measure than other variables, but several participants emphasized the importance of measurements taken at the correct spatial scales and depth. Timing is also important; taking baseline temperature and salinity measurements before and after WEAs are installed can be useful to assess changes. Taking concurrent measurements from non-WEA areas for comparison may also be useful. However, several participants pointed out that the ocean is always changing, making establishing a “baseline” extremely challenging.

Multiple platforms, including fixed systems, buoys, gliders, moorings, aircraft, and satellites can be utilized to take measurements upstream of WEAs, in the WEA area, and downstream. Participants discussed how existing infrastructure could be leveraged to support WEA-scale observations. Turbines already contain monitoring sensors that measure turbulent wind wakes, and these could potentially be adjusted to take additional measurements and support scaling. Substations, which already include meteorological instrumentation, could also provide useful platforms for postconstruction monitoring. Remote sensing technologies such as the Remote Ocean Current Imaging System and the National Aeronautics and Space Administration (NASA) PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite can provide valuable data on phytoplankton blooms, sediment shifts, and other ocean activity, while synthetic aperture radar imagery can also be utilized to gather wind speed measurements.

Characterizing upstream conditions is especially important because this is the input that flows into the WEA; several participants suggested that conducting measurements with long-term, repetitive glider routes could be especially useful for this purpose, although some participants noted that the constant movement can

make data interpretation challenging. Onshore measurements may also be useful if they are adjusted properly. In addition, aircraft and unmanned aerial vehicles can be deployed to take a variety of measurements, and some participants noted that technology supporting turbulence recognition with such platforms is improving. Rapid deployment crafts (water or air) with scanning lidar attached could measure waves and wakes and help with long-term monitoring. Other useful measurement platforms include thermodynamic profilers; ADCPs; drifters, which can help elucidate connectivity between WEAs and other ocean areas; tracers, which can be used to measure diffusion and mixing; and floating lidar buoys or wind cubes, which can be used to measure wind at the surface.

In relation to any WEA-scale efforts, many participants stressed the importance of clearly identifying what measurements or outputs are desired and assessing whether existing observations and process studies can be adjusted to create them. Shipboard surveys, gliders, and satellites are currently being used to measure acoustics, stratification, climate measurements, and more in the region, and data from these sources could potentially be used to connect physical measurements and zooplankton aggregations. Retrospective data of high densities of zooplankton and predators, such as that from environmental DNA (eDNA)¹ or NOAA’s EcoMon plankton datasets,² could also be useful. Some participants also suggested coupling studies of dimethyl sulfide concentrations with other data sources to track zooplankton prey, resolve zooplankton aggregation questions, and potentially even track right whales, although these methods would need to be tested. Understanding physical drivers of zooplankton aggregation would improve knowledge of right whale foraging habitats in the Nantucket Shoals region and thus improve the ability to predict foraging behavior.

Understanding the Biology

Animals are known to align their behavior to water conditions, but there remains much to learn about how and when these responses occur. For zooplankton in particular, open questions include what processes—such as turbulence, internal waves, changes to the water column, large-scale circulation patterns, or changes in predator behavior—impact advection of zooplankton into the region and their aggregation to densities where right whales can feed efficiently, how those aggregations could be measured or modeled, how they are affected by WEAs, and what this may reveal about animal behavior (Visser and Stips, 2002). Some participants suggested that research on prey-seeking migratory birds could be one source for extrapolating information about zooplankton aggregation. Dye release studies offer another opportunity to better understand zooplankton field dynamics and turbulent mixing.

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¹ https://oceanexplorer.noaa.gov/technology/edna/edna.html

² https://www.fisheries.noaa.gov/resource/data/ecosystem-monitoring-northeast-us-continental-shelf-plankton-dataset

In determining what information is needed, some participants suggested that a guiding question is whether Nantucket Shoals can continue to be a suitable right whale habitat. To help answer this question, relevant research directions could include studies to better understand how whales target their feeding areas and the extent to which they are relying on Calanus finmarchicus versus other copepod species. Some aspects of whale behavior are better understood than others. Whales have been documented successfully feeding near WEAs, but some participants noted that further expanding wind energy development still holds the potential to disrupt that behavior, as animals can be impacted by changes at very small scales. One especially important area to monitor is the benthic boundary layer, which can be a mechanism for transporting nutrients into the euphotic zone that are needed to support zooplankton growth. To better understand potential changes in whale feeding patterns, several participants suggested that it could be useful to determine how the sea surface and the subsurface, where both whales and zooplankton feed, may be impacted by wind energy infrastructure.

Finally, some participants suggested that a baseline understanding of animal populations would be helpful in determining whether there are changes at the WEA scale after deployment, positing that population monitoring for zooplankton and whales should be feasible at the WEA scale. Bottom-mounted echo sounders can be used to measure the presence of species, although they cannot be used to isolate zooplankton. Process studies including whale and zooplankton sampling can be especially important for elucidating the fine-scale linkages between ocean physics and biology, which can shed light on larger-scale events.

SYNTHESIS AND DISCUSSION

Participants reconvened from the breakout sessions to synthesize and build upon the discussion of examples of observational needs across scales. Josh Kohut, Rutgers University, and Jeffrey Carpenter, Helmholtz-Zentrum Hereon, provided highlights from the breakout conversations, and attendees engaged in an open discussion to expand upon the common themes and suggestions raised.

At the WEA scale, many participants articulated the importance of measurements that are simple, practical, and feasible to conduct over long periods of time that can be used to isolate wind energy impacts from other changes. Key parameters to measure could include temperature, salinity, currents, wind speed, and wave fields. In addition, the importance of stratification makes it helpful to collect measurements at multiple depths and study processes, such as salinity intrusions at the sea surface, mid-water column, and bottom boundary layers. Measurements taken before construction or in places without wind energy infrastructure could potentially be used to establish baselines or as controls; however, several participants in both groups underscored the challenges of establishing controls in ever-changing ocean systems that are simultaneously experiencing multiple pressures and shifts.

At the turbine scale, participants discussed techniques and instrumentation that could support shorter, targeted process studies. In particular, some participants

noted the importance of differentiating between ocean wake impacts and wind wake impacts by taking measurements with turbines turned off and comparing them with measurements taken when the turbines are operating. In addition to measuring traditional oceanographic and atmospheric parameters, several participants noted the benefits of further refining approaches to measuring turbulence, nutrient presence, and zooplankton aggregations. For example, integrating multiple types of fixed and mobile observation platforms can be important for understanding variability across time and space, and data collected at the turbine scale can become building blocks toward larger-scale models for isolating and assessing WEA impacts. However, several participants also stressed the importance of ensuring that the techniques used to collect data do not inadvertently influence or endanger marine organisms, such as by exposing whales to cables in which they can become entangled.

Members of both breakout groups emphasized the importance of better elucidating the connections between the ocean’s physical properties and biological processes. Such insights could be extremely valuable for predicting how organisms such as zooplankton and whales might change their behavior in response to impacts from wind energy development. However, many fundamental questions remain about the dynamics and impacts of features such as waves, wakes, and zooplankton aggregations; these questions are critical to answer yet challenging to study. Identifying the necessary measurements and how to take them is key, and individuals from both groups underscored the challenges involved in establishing a feasible monitoring program, taking measurements using robust methodology at scale, and interpreting animal behavior.

To advance measurement strategies, observations, and modeling across the field, several participants suggested enhanced collaboration with a feedback-rich knowledge-sharing network. As part of this, several participants highlighted the value of data-sharing and transparency, including adherence to FAIR (findable, accessible, interoperable, reusable) data principles (Wilkinson et al., 2016) and general best practices to make data accessible and user friendly. It is also important to ensure that adequate computational and staff resources are allocated for storing, managing, and analyzing the data, especially for datasets that are large or collected continuously.

Transitioning into an open discussion of short- and long-term observation goals and opportunities, Anthony Kirincich, Woods Hole Oceanographic Institution (WHOI), emphasized the need for process studies at the turbine scale to determine whether the parameterizations and models are appropriate, including for different types of turbines and for changes that may occur as turbines age. For the WEA scale, he added that long-term monitoring is needed to determine how biological activity around the turbine might impact ocean wakes. Jake Kritzer, Northeastern Regional Association of Coastal Ocean Observing Systems (NERACOOS), asked if short-term monitoring at the turbine scale could enable modeling to predict longer-term turbine effects. Kirincich replied that while that would be helpful, long-term monitoring will still be necessary to fully understand the WEA scale.

He also added that process studies will be most effective if benchmark data have already been established and can inform modeling of long-term WEA effects, especially on zooplankton aggregation.

Travis Miles, Rutgers University, suggested that a framework of modifiable process studies could help to elucidate the effects of different foundation designs or regional conditions. Carpenter agreed that given how large the parameter space is, one dataset entered into a model one time will not be enough unless it is modifiable. Kirincich and Grace Saba, Rutgers University, noted that wakes, turbine growth, and stratification all change over time, underscoring the need for requiring repeated measuring and modeling.

While recognizing that WEA and regional-scale studies need to extend long term, likely for decades, Kritzer posited that if the range of local contexts and dynamics can be identified, turbine-scale studies do not necessarily need to continue in the long term once the effects at this scale are well understood. Paula Fratantoni, NOAA, noted that at the turbine scale, large changes can quickly become apparent and prompt agile mitigations and further study. Changsheng Chen, University of Massachusetts Dartmouth, agreed, adding that an accumulation of turbines will significantly impact downwind and ocean wakes. Pak Leung, Shell, posited that one turbine’s effects can be used to extrapolate compound effects, making long-term turbine-scale monitoring unnecessary. He also noted that timescale monitoring will vary and suggested that 1-minute processes or one-turbine effects do not necessarily need to be monitored across multiple years. Kilpatrick pointed out that stratification changes or seasonality can affect individual turbine operations and therefore local effects, making it necessary to revisit turbine-scale measurements after 10–15 years to recalibrate the small-scale dynamics, and Kritzer agreed.

Douglas Nowacek, Duke University, asked about strategies for assessing changes to water flow around turbines, especially close to the ocean floor. Elizabeth Marsjanik, Vineyard Offshore, replied that her company monitors submerged aquatic vegetation for at least 3 years post-construction. She noted that monitoring programs need to be designed in ways that are specific to the water depth and construction techniques used, since different impacts could result depending on whether the foundation involves monopiles, suction buckets, or jackets. Laura Morse, JASCO Applied Sciences, agreed and noted that European research into scour monitoring and protection could also offer useful insights on this topic. Kohut added that tests of nature-inclusive offshore wind designs, which use bio-diverse-enhanced foundations, are underway to examine impacts on biology and habitats; these results could inform future projects. Marsjanik and Morse agreed that it is worth examining the literature on those designs.

Reiterating the central importance of physical–biological interactions, Kohut stated that data from studies of both the turbine and WEA scales can help inform large-scale ecological models connecting ocean physics to zooplankton dynamics. Understanding the mechanistic link through which hydrodynamic processes lead to zooplankton patches would be a powerful tool in the quest to predict how offshore wind farms might impact those dynamics.

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