The Deepwater Exchange Cycle in Indian Arm, British Columbia
Estuarine, Coastal and Shelf Science (1988) 26,285-308 The Deepwater Exchange Cycle in Indian Arm, British Columbia Brad de Young’ and Stephen Pond Department of Oceanography, University of British Columbia, l’amouver, British Columbia, V6T 1 WS, Canada Received 15 September 1986 atld in revisedform September I987 Keywords: fjords; estuarine circulation; diffusion; mixing; hydraulic models; British Columbia Coast A silled fjord on the British Columbia coast, Indian Arm, was used to study the exchange processes controlling deepwater exchange in fiords. Bottom-water renewal took place during the winter of 1984/85. Hydraulic control of the exchange is exerted over the long sill which restricts access to the fjord. The maximum density at the sill occurs during neap tides. No distinct peaks in the velocity at the sill are observed during periods of inflow. Reduced vertical mixing over the long sill during periods of neap tides sets the timing of the bottom water exchange. During each inflow over the 1984/85 winter about 20”,, of the water in the fjord was replaced. These exchanges occurred over periods of 5-10 days. Between the exchange years, diffusion of the water in the basin is important in conditioning the water for the next exchange event. The vertical diffusion coefficient (K,) was determined from an analysis of the salinity data and was found to be related to the buoyancy frequency N by the relationship, KxN-16.D Introduction Captain George Vancouver, after a night anchored in Port Moody, passed the narrows of Indian Arm in 1792 and concluded that it did not provide a navigable route to Europe because of its weak tidal flow.
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