Warm and Cool Nearshore Plumes Connecting the Surf Zone to the Inner Shelf

Cross-shore transport of larvae, pollutants, and sediment between the surf zone and the inner shelf is important for coastal water quality and ecosystems. Rip currents are known to be a dominant pathway for exchange, but the effects of horizontal temperature and salinity gradients are not well understood. Airborne visible and infrared imaging performed on the California coast shows warm and cool plumes driven by rip currents in the surf zone and extending onto the shelf, with temperature differences of approximately 1°C. The airborne imagery and modeled temperatures and tracers indicate that warm plumes exhibit more lateral spreading and transport material in a buoyant near-surface layer, whereas cool plumes move offshore in a subsurface layer. The average cross-shore extent of warm plumes at the surface is approximately one surfzone width larger than for cool plumes. Future work may explore the sensitivity of nearshore plumes to density patterns, wave forcing, and bathymetry.