Variability of internal frontal bore breaking above Opouawe Bank methane seep area (New Zealand).

van Haren, Hans and Greinert, Jens (2013) Variability of internal frontal bore breaking above Opouawe Bank methane seep area (New Zealand). Open Access Geochemistry, Geophysics, Geosystems, 14 (7). pp. 2460-2473. DOI 10.1002/ggge.20170.

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Abstract

Large internal wave breaking is observed exceeding a vertical array of 61 high-resolution temperature sensors at 1 m intervals between 7 and 67 m above the bottom. The array was moored for 5 days at 969 m of Opouawe Bank, New Zealand, a known methane seep area. As breaking internal waves dominate sediment resuspension above sloping topography in other ocean areas, they are expected to also influence methane transport. Despite being visible in single beam echosounder data, indications for turbulence due to rising gas bubbles are not found in the present 1 Hz sampled temperature records. Likely, the mooring was too far away from the very localized bubble release spot. Instead, the temperature sensors show detailed internal wave-turbulence transitions. Every tidal cycle, a solibore (a frontal turbulent bore with a train of trailing solitary waves) changes shape and intensity. These solibores are highly turbulent and they restratify the bottom boundary layer, thereby maintaining efficient mixing. Details of different turbulent bore developments are discussed. Averaged over a few tidal cycles and over the sensors range, mean vertical eddy diffusivity amounts to 3 ± 1 × 10−3 m2 s−1 and mean turbulent kinetic energy dissipation to 1.6 ± 0.7 × 10−7 W kg−1, with variations over 4 orders of magnitude. Such turbulence will affect the distribution of dissolved methane and other geochemical species in the lower 100–150 m above the bottom and their release from the bottom. The above mean values are remarkably similar to those found at various other sites in the NE Atlantic Ocean.

Document Type: Article
Additional Information: WOS:000323828800022
Keywords: large internal wave breaking; methane seep area; high-resolution temperature observations; different solibore developments; Opouawe Bank New Zealand; SO214/2
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems > DeepSea Monitoring
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/ggge.20170
ISSN: 1525-2027
Contribution Number:
ProjectNumber
DSM1
Expeditions/Models/Experiments:
Date Deposited: 10 Jun 2013 10:31
Last Modified: 28 Feb 2018 11:22
URI: http://oceanrep.geomar.de/id/eprint/21371

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