van Haren, Hans (2018): CTD and current meter data from SONNE cruises SO239 and SO240. PANGAEA, https://doi.org/10.1594/PANGAEA.891476, Supplement to: van Haren, H (2018): Abyssal plain hills and internal wave turbulence. Biogeosciences, 15(14), 4387-4403, https://doi.org/10.5194/bg-15-4387-2018
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A 400m long array with 201 high-resolution NIOZ temperature sensors was deployed above a north-east equatorial Pacific hilly abyssal plain for 2.5 months. The sensors sampled at a rate of 1Hz. The lowest sensor was at 7m above the bottom (ma.b.). The aim was to study internal waves and turbulent overturning away from large-scale ocean topography. Topography consisted of moderately elevated hills (a few hundred metres), providing a mean bottom slope of one-third of that found at the Mid-Atlantic Ridge (on 2km horizontal scales). In contrast with observations over large-scale topography like guyots, ridges and continental slopes, the present data showed a well-defined near-homogeneous "bottom boundary layer". However, its thickness varied strongly with time between < 7 and 100ma.b. with a mean around 65ma.b. The average thickness exceeded tidal current bottom-frictional heights so that internal wave breaking dominated over bottom friction. Near-bottom fronts also varied in time (and thus space). Occasional coupling was observed between the interior internal wave breaking and the near-bottom overturning, with varying up- and down- phase propagation. In contrast with currents that were dominated by the semidiurnal tide, 200m shear was dominant at (sub-)inertial frequencies. The shear was so large that it provided a background of marginal stability for the straining high-frequency internal wave field in the interior. Daily averaged turbulence dissipation rate estimates were between 10−10 and 10−9m2s−3, increasing with depth, while eddy diffusivities were of the order of 10−4m2s−1. This most intense "near-bottom" internal-wave-induced turbulence will affect the resuspension of sediments.
Median Latitude: 11.847188 * Median Longitude: -116.972596 * South-bound Latitude: 11.840000 * West-bound Longitude: -117.014830 * North-bound Latitude: 11.860670 * East-bound Longitude: -116.944500
Date/Time Start: 2015-03-10T06:00:00 * Date/Time End: 2015-06-08T11:46:00
SO239_10-1 (CTD3) * Latitude: 11.859170 * Longitude: -117.009830 * Date/Time: 2015-03-20T08:55:00 * Elevation: -4118.7 m * Location: North Pacific Ocean * Campaign: SO239 * Basis: Sonne_2 * Device: CTD/Rosette (CTD-RO)
SO239_2-1 * Latitude Start: 11.844330 * Longitude Start: -116.963170 * Latitude End: 11.844170 * Longitude End: -116.962830 * Date/Time Start: 2015-03-19T14:56:00 * Date/Time End: 2015-03-19T15:30:59 * Elevation Start: -4101.4 m * Elevation End: -4101.0 m * Location: North Pacific Ocean * Campaign: SO239 * Basis: Sonne_2 * Device: Mooring (MOOR)
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Datasets listed in this publication series
- van Haren, H (2018): CTD-profiles from SONNE cruise SO239 and SO240. https://doi.org/10.1594/PANGAEA.892336
- van Haren, H (2018): Current meter data from SONNE cruise SO239. https://doi.org/10.1594/PANGAEA.891474