Publication Date

Summer 2011

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Erika E. McPhee-Shaw

Keywords

bottom boundary layer, internal tide, mixing, Monterey Submarine Canyon, stratification, turbulence

Subject Areas

Physical oceanography

Abstract

Submarine canyons serve an important role as conduits for exchange, funneling sediment and nutrients between shallow shelf waters and the open ocean. The steep and sloping topography intensifies internal waves that dissipate energy directly by friction at the boundary and indirectly when they are reflected and break distant from the boundary. Although bottom boundary layers (BBL) on continental slopes and abyssal regions have been described, deep continental boundary layers are poorly understood. This study examined along-canyon variability in BBL thicknesses and whether BBL heights were related to previously identified regions of high energy dissipation. Temporal variations in BBL thickness were also studied to see if significant variability was associated with an internal tide phase. In August and September 2008, we collected profiles at multiple stations along the Monterey Bay Canyon axis. Measurements included conductivity, temperature and depth (CTD), expendable current profiler (XCP), lowered acoustic Doppler current profiler (LADCP), and vertical microstructure profiler (VMP) profiles of turbulent mixing. BBL heights varied spatially and temporally. BBLs were typically thicker in deeper waters near the Monterey Bend and the canyon mouth; however, heights were not closely in phase with the internal tide. Although turbulence extended 200-300 m above the seafloor, bottom mixed layers were thin or absent. This suggests that stratification and internal tidal oscillations limit the growth of BBLs in the canyon.

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