Publication Date:
2023-06-12
Description:
The rapid increase in offshore wind farm (OWF) structures in the North Sea has precipitated a need for estimates of local ecosystem impacts and to identify the mechanisms of such impacts. The turbulent wakes generated by tidal currents through OWF foundation structures have been shown to reduce stratification and enhance mixing. As seasonal patterns of primary productivity in the North Sea are strongly influenced by summer stratification, the effects of the OWF-structure-induced mixing may have a significant impact on regional biogeochemistry. Using a high-resolution, turbulence-resolving model and in-situ nutrient measurements, we provide estimates of OWF-structure-induced nutrient fluxes and local changes in primary production via an idealized 1-dimensional analysis in the water column. Based on the turbulent diffusivity obtained from Large Eddy Simulations (LES) of OWF-structure-induced turbulence, we compute the flux of nutrients across the pycnocline base from the nutrient-rich, bottom mixed layer into the light-rich, upper layer for various ambient stratification conditions and observed nutrient distributions in the water column. Primary productivity estimates are derived from the additional input of nutrients to more light-abundant layers, using realistic parameters for nutrient and light affinity. We perform sensitivity analyses, comparing the relative impact of the ambient degree of stratification, nutrient distribution, and light conditions, and we identify an upper bound for the primary productivity contribution due to the turbulent wakes of a typical OWF foundation structure. Our results suggest significant contributions to seasonal primary productivity from the anthropogenic turbulence injected across the water column, particularly into the pycnocline.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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