Ocean mixing in deep-sea trenches: New insights from the Challenger Deep, Mariana Trench.

van Haren, Hans, Berndt, Christian and Klaucke, Ingo (2017) Ocean mixing in deep-sea trenches: New insights from the Challenger Deep, Mariana Trench. Deep Sea Research Part I: Oceanographic Research Papers, 129 . pp. 1-9. DOI 10.1016/j.dsr.2017.09.003.

[thumbnail of 1-s2.0-S0967063716304307-main.pdf] Text
1-s2.0-S0967063716304307-main.pdf - Accepted Version
Restricted to Registered users only

Download (1MB) | Contact
[thumbnail of van Haren.pdf] Text
van Haren.pdf - Published Version
Restricted to Registered users only

Download (1MB) | Contact

Supplementary data:

Abstract

Reliable very deep shipborne SBE 911plus Conductivity Temperature Depth (CTD) data to within 60m from the bottom and Kongsberg EM122 0.5° × 1° multibeam echosounder data are collected in the Challenger Deep, Mariana Trench. A new position and depth are given for the deepest point in the world's ocean. The data provide insight into the interplay between topography and internal waves in the ocean that lead to mixing of the lowermost water masses on Earth. Below 5000m, the vertical density stratification is weak, with a minimum buoyancy frequency N = 1.0 ± 0.6 cpd, cycles per day, between 6500 and 8500m. In that depth range, the average turbulence is coarsely estimated from Thorpe-overturning scales, with limited statistics to be ten times higher than the mean values of dissipation rate εT = 3 ± 2 × 10-11 m2 s-3 and eddy diffusivity KzT = 2 ± 1.5 × 10-4 m2 s-1 estimated for the depth range between 10,300 and 10,850m, where N = 2.5 ± 0.6 cpd. Inertial and meridionally directed tidal inertio-gravity waves can propagate between the differently stratified layers. These waves are suggested to be responsible for the observed turbulence. The turbulence values are similar to those recently estimated from CTD and moored observations in the Puerto Rico Trench. Yet, in contrast to the Puerto Rico Trench, seafloor morphology in the Mariana Trench shows up to 500m-high fault scarps on the incoming tectonic plate and a very narrow trench, suggesting that seafloor topography does not play a crucial role for mixing.

Document Type: Article
Keywords: New deepest point estimate; Challenger Deep Mariana Trench; Improved deep CTD observations; Turbulence parameter estimates; Inertio-gravity tidal wave propagation;
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Projects: Ritter Island
Expeditions/Models/Experiments:
Date Deposited: 02 Oct 2017 09:48
Last Modified: 06 Feb 2020 09:07
URI: https://oceanrep.geomar.de/id/eprint/39593

Actions (login required)

View Item View Item