Numerical aspects of water mass structure of wind forced river plumes

Robert Hetland
Texas A&M University

The water mass structure of a river plume is examined using an idealized numerical model of fresh water discharging from an estuary into a continental shelf. It is shown that the river plume may be divided into two distinct regions, categorized by the dominant mixing processes in each zone. The near-field region is where the river plume undergoes active mixing as the estuary discharge spreads and entrains background water through shear mixing. The far-field region is where mixing by the wind is the dominant mechanism for entraining background water into the plume. Entrainment of background waters is greatest in the near-field, where the salt flux is. Shear mixing due to the wind will only mix the upper buoyant layer to a point, after which turbulence due to shear mixing is suppressed. Approximating the plume as a single layer appears to be valid over most of the plume.