How Much Plume Water Released During an Ebb Pulse Interacts with the Plume Front?

We examine details of the connectivity between processes near a river mouth and the dynamics at the seaward boundary of the discharge using the Regional Ocean Modeling System (ROMS). A parameter space spanning different discharge rates, ambient ocean conditions (g’) and wind is investigated with high and low resolution grids of the Merrimack River plume (Newburyport, MA). We evaluate a connectivity parameter defined by the ratio of plume length scale, ranging from the mouth to the front, to a frontal interaction length scale, representing plume water mass interaction with the front, from different plume parameters including velocity, sea surface height and pulsed dye tracers. The percent of plume water released during an ebb pulse that interacts with the front varies with the frontal interaction length scale through parameter space. Source-front connectivity diminishes over an ebb pulse and results suggest that the mechanisms diminishing connectivity include weakening of barotropic gradients through the plume as well as Coriolis effects as the plume becomes geostrophic.