Abstract
Offshore wind construction projects have the potential to alter local and regional physical oceanic processes, via their influence on currents from turbine foundations and by extracting energy from the wind. Hydrodynamic modeling (HDM), particle tracking modeling and Agent-Based Models (ABMs) were used to assess how the introduction of commercial scale offshore wind energy facilities in the Massachusetts-Rhode Island (MA-RI) marine areas may affect local and regional oceanic responses (e.g. currents, temperature stratification) and related larval transport under typical seasonal conditions. The HDM and ABM were developed, calibrated, and verified against a range of observed oceanographic and survey data to demonstrate that related conditions prior to offshore wind construction were well represented by the integrated model. Four post-installation scenarios of a single facility (OCS-A 0501) (Scenario 3), two full build-out scenarios using representative 12 Megawatt (MW) (Scenario 2) and 15 MW turbines (Scenario4) and a mid-level build-out scenario (Scenario 5) were selected for investigation. The results of the HDM study show that the introduction of these structures into the MA-RI offshore area do modify oceanic responses by reducing the current magnitude through added flow resistance, influencing the temperature stratification by introducing additional mixing and reducing the current magnitude and wave height by the extraction of energy from the wind by the OSW turbines. For the key oceanic determinant response for the ABM – current – the HDM showed changes in depth averaged currents varying from Baseline on the order of +11% to -8% in the 75th percentile differences depending on the OSW scenario investigated. These changes in currents, lead to varying degrees of discernable increases and decreases in larval settlement density across the three focal species and four OSW build-out scenarios. Here, depending on the release characteristics of the particular larvae, altered current direction and speeds either act independently and/or collectively to cause the observed shifts. At a regional fisheries management level, these shifts are not considered overly relevant with regards to larval settlement.
The background of the study is the Bureau of Ocean Energy Management’s (BOEM) concerns regarding the potential cumulative impacts on oceanographic transport patterns in the Mid-Atlantic Bight due to the sixteen offshore commercial wind energy leases in southern New England and the Mid-Atlantic. In response, BOEM commissioned this modeling study to assess the changes in hydrodynamic conditions and, among other aspects, fisheries pertinent larval transport impacts resulting from the build-out of one or several OSW energy facilities in the MA-RI lease area.
As suggested above, the key objective of this study was to determine the ‘mesoscale’ effects of offshore wind energy facilities on coastal and oceanic environmental conditions and habitat by examining how oceanic responses will change after turbines are installed, particularly with regards to turbulent mixing, bed shear stress and larval transport.