Internal tides in Whittard Canyon

Aslam, Tahmeena (2017) Internal tides in Whittard Canyon. Doctoral thesis, University of East Anglia.

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Abstract

Submarine canyons are common bathymetric features incising the shelf edge and are
known to trap and focus internal waves leading to high levels of turbulent mixing.
Whittard Canyon, located at the Celtic Sea shelf edge, is a dendritic canyon where
little is known about the internal tide, yet where it is postulated to have a huge
impact on biology within the canyon and also play a role in the generation of
nepheloid layers. High-resolution simulations of the M2 tide in Whittard Canyon
using a modified version of the Princeton Ocean Model are used to determine the
generation, propogation, spatial structure and dissipation of the internal tide within
the canyon. Shamrock canyon and Brenot Spur are identified as key remote sources
of internal tide generation, which modulate local generation in a flux-conversion
feedback mechanism which causes the observed assymmetry in barotropic-tobaroclinic
conversion within the canyon limbs. Depth-integrated baroclinic energy
flux within the canyon is elevated, but variably so in different limbs, with values
reaching >8 kW m¡1. The eastern limb of the canyon is notable for being particularly
energetic. Enhancement of near-bottom baroclinic tidal currents are seen within
the canyon with velocities reaching 0.4 m s¡1. The three-dimensional structure
exhibits bottom intensification due to topographic focusing by the steep canyon
walls, and the dominantly supercritical limb heads. Within the upper canyon the
internal tide exhibits a typical mode-1 structure. Cores of baroclinic energy flux, in
a dominantly up-canyon direction, form over the depth range of 1000-2500 m and
are correlated with potential source regions for nepheloid layers. The sensitivity
of the model to bathymetric resolution is tested and it is found that using 500 m
resolution bathymetry results in domain-averaged conversion rates higher than for
the smoothed bathymetries tested, highlighting the need for high-quality, high-resolution
bathymetric datasets.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Katie Miller
Date Deposited: 06 Jul 2017 14:41
Last Modified: 06 Jul 2017 14:41
URI: https://ueaeprints.uea.ac.uk/id/eprint/64047
DOI:

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