THE RESPONSE OF A STEEP-SIDED, NARROW CANYON TO TIME-VARIABLE WIND FORCING

The response of a relatively narrow (similar to 7 km wide) and deep (s imilar to 450 m deep) steep-sided (up to 45 degrees bottom slope) subm arine canyon to strong wind forcing is explored using data from an 18- element moored array as well as CTD surveys in the vicinity of Astoria submarine canyon. The data are used to describe spatial patterns and phase relationships between lateral velocity, vertical velocity, tempe rature, relative and stretching vorticity, alongshelf wind, and the fl ow incident on the canyon. Upwelling within the canyon is simultaneous and spatially uniform to zero order, and vertical velocity is highly correlated and in phase with alongshelf wind. Vertical velocity within the canyon is not related to flow incident on the canyon except durin g strong upwelling. Above the canyon, temperature, rather than vertica l velocity (time rate of change of temperature), is in phase with wind . Estimated vertical velocities within the canyon were as great as 50 m d(-1) (upward) during upwelling and 90 m d(-1) (downward) during win d relaxation following upwelling events. At depths similar to 100 m ab ove the canyon the flow field is undisturbed by the canyon topography. At depths similar to 40-100 m above the canyon, a cyclonic circulatio n pattern occurs, but only during conditions of weak incident flow (i. e., Rossby number <0.25). At depths similar to 80 m below the canyon r im, cyclonic vorticity is in phase with alongshelf wind and with verti cal velocity: minimum cyclonic Vorticity (or weak anticyclonic vortici ty) is coincident with maximum upwelling and southward (upwelling favo rable) wind, and maximum cyclonic vorticity is coincident with maximum downwelling and minimum southward wind (or weak northward wind).