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Organizers and Hosts:
Matthew Alford, APL-UW, Senior Oceanographer and Affiliate Associate Professor of Oceanography
Jody Klymak, University of Victoria, Assistant Professor, School of Earth and Ocean Sciences


Workshop Focus:
Internal waves are believed to mediate mixing in much of the interior of the ocean, potentially playing a role in driving the Meridional Overturning Circulation and thus affecting the climate. The dominant paradigm is that the internal waves occupy a stochastic and isotropic continuum in frequency and wavenumber space. The form of this wavefield, known as the Garrett–Munk spectrum, is the basis for oft-used parameterizations of turbulence due to Henyey, Gregg, and Polzin.

We revisit these decades-old views in this workshop in light of new numerical, observational, and theoretical findings. Recent attention has focused on narrow and strongly directional peaks in this "universal" spectrum, particularly at the inertial and tidal frequencies. It has been suggested recently that these peaks actually account for the bulk of shear variance in the ocean, with the "continuum" actually a consequence of Doppler shifting of small-scale waves by larger ones. Is this truly the case? If so, what implications does this have for turbulence parameterizations that were developed assuming a continuum?

Attendees*
Matthew Alford, APL-UW
Neil Balmforth, Univ. of British Columbia
Mel Briscoe, OceanGeeks, LLC
Glenn Carter, Univ. of Hawaii at Manoa
Eric D'Asaro, APL-UW
James Girton, APL-UW
Mike Gregg, APL-UW
Toshi Hibiya, Tokyo Univ.
Jody Klymak, Univ. of Victoria
Shaun Johnston, Scripps Inst. of Oceanography
Murray Levine, Oregon State Univ.
Yuri Lvov, Rensselaer Polytechnic Inst.
Jennifer MacKinnon, Scripps Inst. of Oceanography
Jonathan Nash, Oregon State Univ.
JJ Park, Woods Hole Oceanographic Inst.
Tom Peacock, Massachusetts Inst. of Technology
Hartmut Peters, Earth and Space Research, Seattle
Rob Pinkel, Scripps Inst. of Oceanography, Marine Physical Laboratory
Kurt Polzin, Woods Hole Oceanographic Inst.
Luc Rainville, APL-UW
Harper Simmons, Univ. of Alaska, Fairbanks
Lou St. Laurent, Florida State Univ.
Oliver Sun, Scripps Inst. of Oceanography
Bruce Sutherland, Univ. of Alberta
Julie Van der Hoff, Brigham Young Univ.
Hans van Haren, Royal Netherlands Inst. for Sea Research



Recommended Reading:
To put the discussion on a more concrete footing, attendees read or re-read a few relevant articles prior to the workshop. These few articles were selected in an attempt to give some historical perspective and to illustrate the different views possible on the issues considered. Many important articles were omitted from a large literature, to which many of our participants contributed. Please pardon any omissions, and chalk them up to an effort to make a manageable reading list.

1. An argument that much of the continuum results from Doppler smearing of discrete spectral lines:

   R. Pinkel. Advection, phase distortion, and the frequency spectrum of fine-scale fields in the sea. J. Phys. Oceanogr., 38:291-313, 2008.

2. Numerical simulations of energy transfer across a GM spectrum:

   K. B. Winters and E. A. D'Asaro. Direct simulation of internal wave energy transfer. J. Phys. Oceanogr., 27:1937-1945, 1997.

3. Description of the Gregg-Henyey-Polzin parameterization:

   K. L. Polzin, J. M. Toole, and R. W. Schmitt. Finescale parameterizations of turbulent dissipation. J. Phys. Oceanogr., 25:306-328, 1995.