Dynamics of Atmospheres and Oceans 50 (2010) 16–34 Contents lists available at ScienceDirect Dynamics of Atmospheres and Oceans journal homepage: www.elsevier.com/locate/dynatmoce Experimental observation of strong mixing due to internal wave focusing over sloping terrain Arno Swart a,∗ , Astrid Manders b,1 , Uwe Harlander c,2 , Leo R.M. Maas d,e,3 a RIVM - Centre for Infectious Disease Control, Laboratory for Zoonoses and Environmental Microbiology-LZO, P.O. Box 1 (internal mailbox 63), 3720 BA Bilthoven, The Netherlands b TNO Built Environment and Geosciences, Unit Environment, Health and Safety, P.O. Box 80015, 3508 TA Utrecht, The Netherlands c Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology (BTU) Cottbus, Siemens-Halske-Ring 14, D-03046 Cottbus, Germany d Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Texel, The Netherlands e Institute for Marine and Atmospheric Research Utrecht, Buys Ballot Laboratorium, Princetonplein 5, 3584 CC, Utrecht, The Netherlands article info Article history: Received 18 September 2008 Received in revised form 13 August 2009 Accepted 19 August 2009 Available online 3 September 2009 Keywords: Mixing Internal waves Wave attractors Rotating stratified fluids Boundary layers Boundary layer eruptions abstract This paper reports on experimental observation of internal waves that are focused due to a sloping topography. A remarkable mix- ing of the density field was observed. This result is of importance for the deep ocean, where internal waves are believed to play a role in mixing. The experiments were performed on the rotating platform at the Coriolis Laboratory, Grenoble. The rotation, its mod- ulation and density stratification were set to be in the internal wave regime. After applying various data processing techniques we observe internal wave rays, which converge to a limiting state: the wave attractor. At longer time scales we observe a remarkably efficient mixing of the density field, possibly responsible for driv- ing observed sheared mean flows and topographic Rossby waves. We offer the hypothesis that focusing of internal waves to the wave attractor leads to the mixing. © 2009 Elsevier B.V. All rights reserved. ∗ Corresponding author. Tel.: +31 030 274 2090. E-mail addresses: arno.swart@rivm.nl (A. Swart), astrid.manders@rivm.nl (A. Manders), haruwe@tu-cottbus.de (U. Harlander), maas@nioz.nl, l.r.m.maas@uu.nl (L.R.M. Maas). 1 Tel.: +31 88 8662260. 2 Tel.: +49 355 695121; fax: +49 355 694891. 3 Tel.: +31 222 369419/30 253 2715; fax: +31 222 319674/30 254 3163. 0377-0265/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.dynatmoce.2009.08.003