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Diapycnal mixing and the internal wave field north of the Kerguelen Plateau

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Meyer, Amelie (2014) Diapycnal mixing and the internal wave field north of the Kerguelen Plateau. PhD thesis, University of Tasmania.

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Abstract

Dissipating internal waves are the main source of mixing in the stratified
ocean. Recent observational and modelling studies in the Southern Ocean
primarily associate the generation of internal waves with either wind forcing
or with rough topography. This work explores the nature of mixing and its
sources north of the Kerguelen Plateau, a large topographic feature in the
Southern Ocean. Based on novel observations, we present the distribution
and intensity of mixing, and the internal wave field properties.
This thesis includes (i) a regional description of the Kerguelen Plateau
oceanographic characteristics; (ii) estimates of mixing and its sources; and
(iii) a study of the internal wave field in the vicinity of the Plateau. The
data consist of 914 temperature, salinity, pressure and horizontal velocity
profiles from Electromagnetic Autonomous Profling Explorer (EM-APEX)
floats deployed northeast of the Kerguelen Plateau in 2008. We are able
to estimate diapycnal mixing in the upper 1600m of the water column. To
estimate mixing, we apply both a Thorpe-scale analysis on density inversions
and a shear-strain parameterization method and compare the estimates with
direct microstructure measurements.
The observational results provide the first clear connection between the
distribution and intensity of mixing, and the associated internal wave field
properties. In the Kerguelen Plateau area, mean mixing from the EM-APEX
data is slightly larger (diffusivity of O(10-5m2s-1) than typical open-ocean
background levels. Mixing intensities show strong spatial and temporal variability
reaching considerably large values close to the Plateau (di�usivity of
O(10

Item Type: Thesis (PhD)
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Date Deposited: 15 Dec 2014 04:33
Last Modified: 11 Mar 2016 05:52
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