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Sensitivity of the Ocean State to Lee Wave–Driven Mixing

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Melet, A and Hallberg, R and Legg, S and Nikurashin, M Sensitivity of the Ocean State to Lee Wave–Driven Mixing. Journal of Physical Oceanography, 44. pp. 900-921. ISSN 1520-0485

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Abstract

Diapycnal mixing plays a key role in maintaining the ocean stratification and the meridional overturning
circulation (MOC). In the ocean interior, it is mainly sustained by breaking internal waves. Two important
classes of internal waves are internal tides and lee waves, generated by barotropic tides and geostrophic flows
interacting with rough topography, respectively. Currently, regarding internal wave–driven mixing, most
climate models only explicitly parameterize the local dissipation of internal tides. In this study, the authors
explore the combined effects of internal tide– and lee wave–driven mixing on the ocean state. A series of
sensitivity experiments using the Geophysical Fluid Dynamics Laboratory CM2G ocean–ice–atmosphere
coupled model are performed, including a parameterization of lee wave–driven mixing using a recent estimate
for the global map of energy conversion into lee waves, in addition to the tidal mixing parameterization. It is
shown that, although the global energy input in the deep ocean into lee waves (0.2 TW; where 1 TW51012W)
is small compared to that into internal tides (1.4 TW), lee wave–driven mixing makes a significant impact on
the ocean state, notably on the ocean thermal structure and stratification, as well as on the MOC. The vertically
integrated circulation is also impacted in the Southern Ocean, which accounts for half of the lee wave
energy flux. Finally, it is shown that the different spatial distribution of the internal tide and lee wave energy
input impacts the sensitivity described in this study. These results suggest that lee wave–driven mixing should
be parameterized in climate models, preferably using more physically based parameterizations that allow the
internal lee wave–driven mixing to evolve in a changing ocean.

Item Type: Article
Journal or Publication Title: Journal of Physical Oceanography
Page Range: pp. 900-921
ISSN: 1520-0485
Identification Number - DOI: 10.1175/JPO-D-13-072.1
Additional Information:

Copyright 2013 American Meteorological Society

Date Deposited: 20 May 2014 05:47
Last Modified: 18 Nov 2014 05:00
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