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Partly standing internal tides in a dendritic submarine canyon observed by an ocean glider

Hall, Rob A.; Aslam, Tahmeena; Huvenne, Veerle. 2017 Partly standing internal tides in a dendritic submarine canyon observed by an ocean glider. Deep Sea Research Part I: Oceanographic Research Papers, 126. 73-84. 10.1016/j.dsr.2017.05.015

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© 2017 Elsevier B.V. This is the author’s version of a work that was accepted for publication in Deep Sea Research Part I: Oceanographic Research Papers. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was/will be published in Deep Sea Research Part I: Oceanographic Research Papers (doi:10.1016/j.dsr.2017.05.015)
Hall_et_al_2017_Partly_standing_internal_tides_DSRI_authors_copy.pdf - Accepted Version
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Abstract/Summary

An autonomous ocean glider is used to make the first direct measurements of internal tides within Whittard Canyon, a large, dendritic submarine canyon system that incises the Celtic Sea continental slope and a site of high benthic biodiversity. This is the first time a glider has been used for targeted observations of internal tides in a submarine canyon. Vertical isopycnal displacement observations at different stations fit a one-dimensional model of partly standing semidiurnal internal tides – comprised of a major, incident wave propagating up the canyon limbs and a minor wave reflected back down-canyon by steep, supercritical bathymetry near the canyon heads. The up-canyon internal tide energy flux in the primary study limb decreases from 9.2 to 2.0 kW m−1 over 28 km (a dissipation rate of 1−2.5×10−7Wkg−1 ), comparable to elevated energy fluxes and internal tide driven mixing measured in other canyon systems. Within Whittard Canyon, enhanced mixing is inferred from collapsed temperature-salinity curves and weakened dissolved oxygen concentration gradients near the canyon heads. It has previously been hypothesised that internal tides impact benthic fauna through elevated near-bottom current velocities and particle resuspension. In support of this, we infer order 20 cm s−1 near-bottom current velocities in the canyon and observe high concentrations of suspended particulate matter. The glider observations are also used to estimate a 1 °C temperature range and 12 μmol kg−1 dissolved oxygen concentration range, experienced twice a day by organisms on the canyon walls, due to the presence of internal tides. This study highlights how a well-designed glider mission, incorporating a series of tide-resolving stations at key locations, can be used to understand internal tide dynamics in a region of complex topography, a sampling strategy that is applicable to continental shelves and slopes worldwide.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.dsr.2017.05.015
ISSN: 09670637
Date made live: 17 Aug 2017 16:20 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/517638

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