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Impact of internal wave drag on the semidiurnal energy balance
Maarten C. Buijsman, Joseph K. Ansong, Brian K. Arbic, Patrick G. Timko, Caitlin B. Whalen, ZhongXiang Zhao
University of Southern Mississippi
(Abstract received 04/20/2015 for session X)
ABSTRACT
The effects of a parameterized linear internal wave drag on the semidiurnal barotropic and baroclinic energetics of a realistically forced three-dimensional global ocean model are analyzed. Although the main purpose of the parameterization is to improve the surface tides, it also influences the internal tides. The coarse resolution of ∼ 8 km only permits the generation and propagation of the first three vertical modes. Hence, this wave drag parameterization represents the energy conversion to and the subsequent breaking of the unresolved high modes. Although the total tidal energy input is in agreement with TPXO, an accurate satellite-altimetry constrained model, the energy lost to the internal tides in deep water and bottom friction on the shallow shelves are respectively larger and smaller than the dissipation estimates from TPXO. Moreover, the wave drag overestimates the high-mode conversion at ocean ridges against regional high-resolution models. The wave drag also damps the low- mode internal tides as they propagate away from their generation sites. Hence, it can be considered a scattering parameterization, causing more than 50% of the deep water dissipation of the internal tides. In the near field, most of the baroclinic dissipation is attributed to viscous and numerical dissipation. The far field, decay of the simulated internal tides is in agreement with satellite altimetry and falls within the broad range of Argo-inferred dissipation rates. In the simulation about 12% of the semidiurnal internal tide energy generated in deep water reaches the continental shelves.
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2015 LOM Workshop, Copenhagen, Denmark June 2nd - 4th, 2015