Exchange Flows in Tributary Creeks Enhance Dispersion by Tidal Trapping

Abstract The North River estuary (Massachusetts, USA) is a tidal marsh creek network where dispersion processes dominate the salt balance. A field study using moorings, shipboard measurements, and drone surveys was conducted to characterize quantify trapping due tributary creeks. During flood tide, saltwater propagates up main channel gets “trapped” in creeks inherit an axial salinity gradient from time-varying at their boundary with channel, but it stronger than of because relatively weaker currents. drives baroclinic circulation that stratifies creeks, while remains well-mixed. Because creeks’ shorter geometries, currents lead those channel; therefore, never fill saltiest water which passes junction. This velocity phase difference enhanced by exchange flow fast-tracks fresher surface layer back channel. Through ebb fresh outflows introduce negative anomaly into advected downstream tide. Using high-resolution we empirically determine resulting its calculate rate trapping. Our larger theoretical estimates neglect Trapping contributes more half landward flux this region.