UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Water properties, currents and zooplankton distribution over a submarine canyon under upwelling-favorable conditions Vindeirinho, Carine

Abstract

Two canyons (Juan de Fuca and Barkley) off the west coast of Vancouver Island show enhanced upwelling during the summer. Barkley Canyon is also a region of zooplankton aggregation. An intensive survey was conducted to characterize their circulation, water properties and, for Barkley, zooplankton distribution. CTD casts and zooplankton tows were performed in 1997 around Barkley Canyon. Current meter moorings were positioned within both canyons (Juan de Fuca in 1993 and Barkley in 1997). The circulation in Juan de Fuca Canyon is characterized by a southeastward flow at 30 and 75 m but a northward, in-canyon flow at 200 m. The deep flow supports a strong and consistent upwelling from May to October with a strong decrease in temperature equivalent to a 200-m vertical displacement. The northward-flowing California Undercurrent is found to have no significant influence on the upwelling. In Barkley Canyon, there is a weaker upwelling signal that nonetheless explains an important variance in the CTD data. Isopleths upwell towards the head of the canyon and dome over it near the surface. This implies that the influence of the canyon reaches shallower depths than in Astoria Canyon, for example. The circulation of the canyon is assessed from the mooring data: the flow bends over the canyon at 150 m, with a possible cyclonic eddy at the head, while the current is mainly cyclonic at depth. Some in-canyon flow events are observed, which result in moderate upwelling. Zooplankton are found to aggregate along the walls near the head and mouth of Barkley Canyon with different distribution patterns according to the species' vertical and spatial preferences. Interaction with the circulation, especially the deep cyclonic flow, seems to play an important role in this aggregation.

Item Media

Item Citations and Data

Rights

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.