Abstract
A globally growing Blue Economy, including offshore energy development, requires a baseline understanding of regional oceanographic conditions and current flow fields before installation to be able to evaluate sites and assess impacts on coastal ecosystems. We leverage more than a decade (2012–2022) of high-resolution surface current measurements from a high-frequency radar network along the central California continental shelf, including a previously designated Wind Energy Area (WEA), to characterize seasonal current circulation and identify seasonal patterns in coherent transport structures using a Lagrangian framework. Finite-time Lyapunov exponents (FTLEs) are calculated from surface currents to identify Lagrangian coherent structures (LCS) and characterize seasonal patterns in attracting (convergent) and repelling (divergent) transport structures in the WEA. Mean current patterns exhibited a strong seasonal cycle, with a pronounced transition from relatively weak poleward flow in the winter months to strong equatorward flows during the spring months, before currents relaxed into the late summer and fall. Coincident with the onset of the upwelling season in the spring was a distinct increase in both attracting and repelling FTLE fields, particularly near the coastline, with elevated values extending offshore into the WEA. Attracting ridges exhibited a greater spatial extent and occurrence within the WEA compared to repelling ridges, suggesting a greater propensity for material aggregation (versus dispersal) and prey aggregation (and potential ecological hotspots). These patterns have critical implications for ecosystem dynamics, pollutant transport, and environmental risk in and around the WEA. The analysis presented here could enable the future integration of dynamic oceanographic information, including transport structures derived from the growing international HFR network, into future marine spatial planning, environmental risk assessment, and ecosystem-based management.