The Simulation of Deep Water Exchange in a Fjord: Indian Arm, British Columbia, Canada

Abstract

A numerical model is used to simulate deep water renewals that were observed to occur in Burrard Inlet/Indian Arm over a time period of about 100 days during winter 1984/85. The renewals (bottom water flowing from Burrard Inlet into Indian Arm) occurred (or intensified) during neap tide and caused a steady increase in the density near the bottom in Indian Arm. The model successfully reproduces the renewal events for a simulation time of at least 85 days. It uses a Mellor?Yamada, level-two turbulence closure scheme, for which the local turbulent energy production is balanced by local dissipation, and for which the turbulent length scale is prescribed. The length scale varies linearly with depth near the surface and bottom and is constrained to never be larger than 1) 20% of the water depth and 2) the Ozmidov length scale. A lower bound is imposed on the vertical diffusion coefficients that depends on the Brunt?Väisälä frequency N. Its magnitude, for a given N, is different in Burrard Inlet and in Indian Arm, and it was estimated from observed variations in the scalar fields. When the influence of horizontal variations in the alongchannel velocity on the turbulent energy production is taken into account, the model simulates the observations more accurately.