Offshore Wind Sustained Observation Programme (OW-SOP): scoping report

Executive summary

The Scottish Government, through the Offshore Wind Directorate, commissioned the National Oceanography Centre (NOC) to undertake a project to provide recommendations for designing a programme of sustained observations of physical and biogeochemical water column processes. This project’s objective is to improve the evidence base and support the sustainable development of the offshore wind (OW) industry within, but not limited to, the Scottish sector of the North Sea. The project included a review of the current state of knowledge about the North Sea water column structure, previous and ongoing observational programmes, and current efforts in understanding the interaction between fast-growing, large-scale infrastructures and the ocean environment. This review highlighted existing data, knowledge gaps, and the role that models could play. These ultimately feed into recommendations for the appropriate methodology necessary to assess the potential impact of offshore wind farms (OWFs) (and especially floating offshore wind farms, FLOW) being developed in deeper seasonally stratified shelf sea waters. These impacts could include changes to the physical and biogeochemical properties of the water column, which could impact the wider ecosystem.

Recommendations on the use of modelling approaches, on the ‘best-practice’ for sustained observation programmes and a roadmap towards their implementation have been proposed both through review of academic literature and a stakeholder engagement workshop.

This final report provides an overview of the development landscape in the Scottish North Sea and a review of the current state of knowledge, before a series of recommendations, which can be summarised as follows:

i. Existing and new data from observational/monitoring programmes should be used in conjunction with models to predict impact, provide guidance on future observational/monitoring efforts, and validate model predictions at shelf-wide (regional) and site-specific (OWF project) scales.

ii. Existing data on water column physical and biogeochemical parameters (including data from OW, O&G, fisheries, etc.) should be accessible from data repositories ideally managed by public bodies and should follow international standards of Findability, Accessibility, Interoperability and Reusability (FAIR) for data formats.

iii. The observation of fundamental EOVs at shelf-scale (regional) and site-specific (OWF project) scales should be prioritised and parameters have been proposed.

iv. 3D models can support our understanding of the water column baseline conditions (in absence of OWFs). Existing, and new, observational data from the vicinity of OWFs should be used to parametrise, refine and validate model outputs.

v. 3D far-field hydrodynamic models, using existing data, taking a ‘precautionary approach’ to the mixing effects due to OWFs, could be used in project scoping and EIAs to assess the potential levels of mixing due to infrastructure. These models could be augmented by site-specific modelling performed by developers.

vi. Models’ recommendations should guide future observational/monitoring programmes focusing on the transition between mixed and stratified water columns (spring/autumn), as well as throughout the stratified period (summer). Transition zones where there is marginal water column stability or intermittent stratification (e.g. changes through spring-neap cycle) should also be monitored and data used to parameterise and validate models.

vii. Future programmes should use a combination of fixed (e.g. moorings), dynamic (e.g. marine autonomous systems (MAS), ship based) and/or remote (e.g. satellite data) platforms and sensors, prioritising sustained observations from fixed platforms at/near early OWFs in stratified waters. The addition of Conductivity, Temperature, Depth (CTD) sensors to other planned, or existing, moorings (e.g. marine mammal/passive acoustic detection moorings and eDNA) should be considered in order to contribute to the understanding of stratification in an efficient and cost-effective manner. Similarly, the collection of additional biological data on moorings primarily designed for physical process monitoring, could be cost efficient and generate complementary datasets. Relevant sampling duration(s) and recommended temporal and spatial resolutions are provided in this report, where possible.

viii. Monitoring plans should look beyond the project level and consider strategic sustained observations. This report considers potential funding mechanisms for such programmes.

ix. Observational and impact modelling guidelines require further definition.

These recommendations aim to support the implementation of sustained observations at regional and site-specific scales. It is important to fully understand the potential OWF-induced changes to the environment, and for this, models are key. Water column changes may also impact higher trophic levels and the wider ecosystem; however, discussions around the potential impact to seabed, pelagic and benthic communities, etc. is out of the scope of this project. This report focuses discussion on the possible interaction between OW activities and the physical and biogeochemical structure of the water column only.

The recommendations presented in this report, and the associated qualitative assessment presenting ‘best-to-worst’ case scenarios for implementation, should be integrated within existing assessments to inform project level Environmental Impact Assessments (EIA), Habitat Regulation Appraisals (HRA) and Strategic Environmental Assessments (SEA) for offshore developments to support future planning work. This guidance is intended to be used to make recommendations for best practice only.