Recent sediment dynamics in hadal trenches: Evidence for the influence of higher-frequency (tidal,near-inertial) fluid dynamics |
| |
| Affiliation: | 1. Scottish Association for Marine Science, Oban PA37 1QA, UK;2. Stockholm University, Department of Meteorology, 106 91 Stockholm, Sweden;3. Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Marine Technology and Engineering Center, 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan;4. University of Southern Denmark, Nordic Centre for Earth Evolution, 5230 Odense M, Denmark;5. Greenland Climate Research Centre, 3900 Nuuk, Greenland;6. University of Copenhagen, Marine Biological Section, 3000 Helsingør, Denmark;7. Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan;8. Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany;9. Alfred-Wegener-Institute for Polar and Marine Research, 27570 Bremerhaven, Germany,;10. Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan;1. Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, 305-8567, Japan;2. R&D Center for Earthquake and Tsunami, Japan Agency of Marine Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan;3. Fukushima University, Kanayagawa, 1, Fukushima, 960-1296, Japan;4. Institute of Geology, University of Innsbruck, Innrain 52, Raum 6O 305, 6020 Innsbruck, Austria;5. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359 Bremen, Germany;6. Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, 060-0810, Japan;1. Institute of Biological and Environmental Sciences, University of Aberdeen, Zoology Building, Aberdeen AB24 2TZ, UK;2. Oceanlab, University of Aberdeen, Newburgh, Aberdeenshire AB41 6AA, UK;1. Royal Netherlands Institute for Sea Research (NIOZ) and Utrecht University, P.O. Box 59, 1790 AB Den Burg, the Netherlands;2. GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany |
| |
| Abstract: | In addition to high hydrostatic pressure, scarcity of food is viewed as a factor that limits the abundance and activity of heterotrophic organisms at great ocean depths, including hadal trenches. Supply of nutritious food largely relies on the flux of organic-rich particulate matter from the surface ocean. It has been speculated that the shape of hadal trenches helps to ‘funnel’ particulate matter into the deeper parts of the trench, leading to sediment ‘focussing’ and improved benthic food supply. Here we investigate for five Northwest Pacific trenches the efficiency of sediment focussing by evaluating ratios of measured (sediment-derived) and expected (water-column-derived) sedimentary inventories of the naturally occurring and radioactive particulate-matter tracer 210Pbxs. The sites comprise a broad range of surface-ocean productivity and physical-oceanographic regimes. Across the five trench-axis settings the inventory ratio varies between 0.5 and 4.1, with four trench-axis settings having ratios>1 (sediment focussing) and one trench-axis setting a ratio<1 (sediment winnowing). Although the fluid- and sediment-dynamical forcing behind sediment focussing remains unclear, this study finds evidence for another mechanism that is superimposed on, and counteracts, the focussing mechanism. This superimposed mechanism is related to higher-frequency (tidal, near-inertial) fluid dynamics. In particular, there is evidence for a strong and negative relation between the intensity of propagating internal tides and the extent of sediment focussing in the trench-axis. The relation can be approximated by a power function and the most intense drop in sediment focussing already occurs at moderate internal-tide intensities. This suggests that propagating internal tides may have a subtle but significant influence on particulate-matter dynamics and food supply in hadal trenches in particular, but possibly also in the deep seas in general. A mechanism for the influence of internal tides on sediment dynamics is proposed. |
| |
| Keywords: | Hadal trench Benthos Sediment Inertial oscillation Internal tide |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
