THE INFLUENCE OF WINDS AND TIDES IN THE FORMATION OF CIRCULATION LAYERS IN A BAY, A CASE-STUDY - CONCEPCION-BAY, CHILE

Horizontal water velocities were measured using three current meters m oored at the levels of 5, 18, and 30 m depth in the oriental side of C oncepcion Bay (36 degrees 40'S; 73 degrees 02'W), an almost rectangula r, shallow bay off central Chile, connected with the open sea through two mouths. The large momentum transfer from the wind to the water cau ses variations of the internal volume of the bay generating circulatio n layers having almost anti-parallel directions. Northerly winds carry superficial water into the bay, causing a compensating flow leaving t he bay near its bottom. Winds from the SW, on the other hand, cause an outgoing circulation layer in the surface and a circulation layer ent ering into the bay near the bottom. During wind calm periods, longer t han 12 h, the two layers disappear, leaving a current system comprisin g only one circulation layer. The response time necessary for the gene ration or dissipation of these layers, which fluctuates between 1 and 7 h, depends on the initial conditions of the bay and on the intensity , direction and persistence of the wind. (C) 1997 Academic Press Limit ed.