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SUMMARY:EESS talk on "High-resolution observations of internal wave induce
 d turbulence in the deep ocean"
DTSTART:20161011T121500
DTEND:20161011T131500
DTSTAMP:20261001T234517Z
UID:ef4cd7f23210762b0890cdbdb5dbe82c01371fcd263ca4e9b9ecd7e1
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Hans van Haren\, Ocean Systems Sciences (OCS)\, Royal Nethe
 rlands Institute for Sea Research - NIOZ\, Texel (NL)\nAbstract: An overvi
 ew is presented of high-resolution temperature observations above underwat
 er topography in the deep\, stably stratified ocean. The Eulerian mooring 
 technique is used to monitor temperature variations by typically 100 senso
 rs distributed over lines between 40 and 400 m  long. The independent sen
 sors sample at a rate of 1 Hz for up to one year with a precision better t
 han 0.1 mK. This precision and sampling rate are sufficient to resolve the
  large\, energy containing turbulent eddies and all of the internal waves 
 and their breaking above underwater topography. Such underwater wave break
 ing is the key mechanism for the redistribution of nutrients and heat (to 
 maintain the ocean stably stratified)\, and the resuspension of sediment.\
 nUnder conditions of tight temperature-salinity (temperature-density) rela
 tionship\, the temperature data are used to quantify turbulent overturns. 
 These observations show two distinctive turbulence processes that are asso
 ciated with different phases of a large-scale (mainly tidal) internal grav
 ity wave: i) highly nonlinear turbulent bores during the upslope propagati
 ng phase\, and ii) Kelvin-Helmholtz billows\, at some distance above the s
 lope\, during the downslope phase. While the former may be associated in p
 art with convective turbulent overturning following Rayleigh-Taylor instab
 ilities\, the latter are mainly related to shear-induced instabilities. Un
 der weaker stratified conditions\, away from boundaries\, free convection 
 is the more dominant mixing process observed. With a newly developed five-
 lines mooring\, the transition from isotropy (full turbulence) to anisotro
 py (stratified turbulence/internal waves) is revealed.\n\nShort biography:
  Hans van Haren is a senior scientist at the Royal Netherlands Institute o
 f Oceanography (NIOZ). He graduated from Utrecht University\, completing h
 is MsC (physics and geophysics—physical oceanography) in 1985 and PhD in
  1990 (working at NIOZ). He worked as a Post-Doc in Canada 1990-1992 with 
 Chris Garrett and Neil Oakey\, first at Dalhousie University and Bedford I
 nstitute of Oceanography (Halifax)\, later at University of Victoria (BC).
  In 1992 he returned to NIOZ\, first 3 years as Post-Doc\, from 1995 onwar
 ds as permanent staff. His work is on ocean observations\, including devel
 opment of new instrumentation\, and focusing on the study of turbulent exc
 hange processes governed by internal waves and affecting ocean life. Over 
 the years\, he has participated and led more than 50 sea-campaign cruises\
 , varying from shallow seas like the North Sea and Baltic to deep open Atl
 antic Ocean.
LOCATION:GR A3 31 http://plan.epfl.ch/?room=GR%20A3%2031
STATUS:CANCELLED
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