Offshore wind farms could impact coastal marine heatwaves in eastern boundary upwelling systems

Analysis of ecosystem impacts from offshore wind (OSW) farm development has primarily focused on localized effects. However, in Eastern Boundary Current Upwelling Systems (EBUS) like the California Current, OSW farms can modify the intensity and spatial structure of wind-driven upwelling, inducing non-local (tens of kms away) changes to seawater temperature. Recent numerical modeling research determined that a hypothetical upper bound full buildout of OSW farms in central California could warm coastal waters through a reduction in upwelling. Here, we examine the sensitivity of coastal marine heatwaves (MHWs), which are prolonged extreme seawater temperatures that are among the greatest threats to marine ecosystems, to seawater temperature increases motivated by OSW-induced warming. Using a novel long-term coastal water temperature record spanning over four decades, we find that there is the potential for significant increases in MHW days, with individual MHWs becoming more intense and prolonged. Although the exact nature of OSW-induced changes to MHWs are uncertain, this is the first investigation into the potential impacts of OSW development on coastal MHWs, with important implications for marine ecosystems in EBUS globally where OSW is being considered. Despite the potential impacts, OSW remains a critical component to combat the much more pervasive issue of global climate change. • First study on impacts of offshore wind (OSW) farms on marine heatwaves (MHWs) • Sensitivity analysis of MHWs to OSW farm induced warming scenarios • Full buildout in central CA could increase MHW days, intensities, and durations • Non-local ecosystem impact of OSW in eastern boundary current upwelling systems