Nearshore Lagrangian Connectivity: Submesoscale Influence and Resolution Sensitivity

Abstract

AbstractRealistic simulation of nearshore (from the shoreline to approximately 10‐km offshore) Lagrangian material transport is required for physical, biological, and ecological investigations of the coastal ocean. Recently, high‐resolution simulations of the coastal ocean have revealed a shelf populated with small‐scale, rapidly evolving currents that arise at resolutions 100 m. However, many historical and recent investigations of coastal connectivity utilize circulation models with ≈1‐km resolution. Here we show a resolution sensitivity to simulated Lagrangian transport and coastal connectivity with a hierarchy of Regional Oceanic Modeling System simulations of the Santa Barbara Channel at Δx= 1, 0.3, 0.1, and 0.036 km. At higher resolution ( 100 m), rapid alongshore and vertical transport occurs in regions less than 1 km from the shoreline due to submesoscale shelf currents that open up new transport pathways on the shelf: submesoscale fronts and filaments, topographic wakes, and narrow alongshore jets. Shallow‐water fronts and filaments induce early time downwelling and subsequent dispersal at depth of surface material; this is not captured at coarser resolution (Δx= 1 km). Differences in three‐dimensional and two‐dimensional transport are explored in a higher‐resolution simulation: In general, three‐dimensional trajectories are more dispersive than two‐dimensional, due to a separation in their respective trajectories.