Abstract
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A vertical array of fast-response temperature sensors was deployed
to investigate interior ocean temperature and thermal stratification
variability during Spring, 2018 near an inlet entrance on the Otago
inner continental shelf (15 m water depth). Over the 24-day
observation period, the background water column structure
evolved from supporting a near-surface pycnocline, to being
characterised by a deep surface mixed layer. Periods of mostly
low stratification due to atmospheric- and surface wave-driven
mixing are also observed. Time-varying normal-mode projection
demonstrates that the vertical structure of semi-diurnal
temperature oscillations evolves in response to this background
stratification in a manner consistent with the interpretation of
internal waves. At higher frequencies (supratidal) the projection is
less consistent as vertically coherent oscillations from non-linear
internal solitons co-exist with non-coherent oscillations, a
potential signature of stratified mixing. Although both processes
are likely important contributors to the transport of coastal
tracers and inlet-ocean exchange, further measurements are
needed to determine the origin and fate of internal waves on the
Otago continental shelf.