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| Titel |
Overflow induced turbulence in a deep ocean channel |
| VerfasserIn |
Sandra Tippenhauer, Marcus Dengler, Tim Fischer, Torsten Kanzow |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111365
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| Publikation (Nr.) |
 EGU/EGU2015-11472.pdf |
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| Zusammenfassung |
| Diapyncal mixing processes in a deep ocean channel in the Lucky Strike region are
investigated using microstructure data collected by an autonoumous underwater vehicle
(AUV), moored current time series, lowered ADCP profiles and lowered CTD profiles. The
distribution of the flow, the density, and the dissipation rate of turbulent kinetic energy in a
deep ocean channel in the central valley of the Mid-Atlantic Ridge near 37°N is presented.
Within the channel, mostly unidirectional, northward flow across a sill was present. The
spatial distribution of the dissipation rate inside the channel was inferred using a horizontally
profiling microstructure probe attached to an AUV. To the authors’ knowledge, this is the
first successful realization of a horizontal, deep-ocean microstructure survey. The
magnitude of the dissipation rate was distributed asymmetrically relative to the
position of the sill. Elevated dissipation rates were present in a segment 1 to 4 km
downstream of the sill with peak values of 1 /
10-7ÂW/kg. Flow speeds with a
maximum of 20Âcm/s and elevated density finestructure were observed within the same
segment. Lowered and moored velocity observations showed large variability on
semi-diurnal time-scales. The measurements indicated hydraulic controlled flow to
be established at least temporarily downstream of the sill. If hydraulic control is
established a hydraulic jump is expected to occur downstream. Consistently, an
upward displacement of the isopycnals was observed in the area where the hydraulic
jump is expected from the velocity distribution. The spatial distributions of the
flow, density and dissipation rate provide a consistent picture indicating deep-ocean
mixing to depend heavily on the local bottom topography and flow conditions.
Furthermore, the results nicely illustrate that horizontally-profiling AUV-based
observations may be an efficient tool to study deep-ocean turbulence over complex terrain. |
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