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03.07.2023: online Ocean Circulation and Climate Dynamics Colloquium
Dr. Hans van Haren, Senior Scientist NIOZ, Royal Netherlands Institute for Sea Research: "Deep-ocean internal wave turbulence observations using a kilometer-long thermistor string"
When? Monday, 3 July 2023 at 11 am
Where? online via zoom
Abstract:
The stable density-stratified ocean-interior shows omnipresent internal waves that affect redistribution of heat, nutrients and suspended matter, mainly by turbulent breaking above extensive seafloor topography. Growing evidence suggests that the resulting turbulent mixing is sufficient to maintain the ocean’s stratification, thereby preventing the deep-ocean from becoming a stagnant pool of cold water. The presentation will briefly introduce how internal wave turbulence can be observed using high-resolution temperature sensors on a sub-surface mooring line. Focus is on results from a >1-km long string holding 760 sensors above a 2380-m seafloor of Mount Josephine NE-Atlantic. Largest mean turbulence values are found near the seafloor. Local increases of mean turbulence values are observed in bands of 100-200 m thickness. Larger internal wave breaking occurs during baroclinic spring tide, which also affects internal waves and turbulent overturning in the interior. Spectrally, a turbulence inertial subrange dominates part of the internal wave band continuum near the seafloor. Coupling between interior- and near-seafloor-mixing is not only via previously suggested isopycnal transport of mixed waters, but also via strong internal wave interactions. Seamount-flow contributes to absolute vorticity so that blue-shifted near-inertial motions interact with internal tides. If time allows, some exotic observations will be presented.
