Open-ocean response and normal mode excitation in an eddy-resolving general circulation model |
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| Authors: | Arthur J Miller William R Holland Myrl C Hendershott |
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| Institution: | 1. Scripps Institution of Oceanography , IGPP A-025, La Jolla, CA 92093, U.S.A.;2. The National Center for Atmospheric Research , Boulder, CO 80307, U.S.A. |
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| Abstract: | Abstract Analysis of a two-layer, flat-bottom, steady-wind driven, eddy-resolving general circulation model reveals a distinct separation in frequency of baroclinic and barotropic motion in the region distant from the model Gulf Stream. The far-field motions at periods less (greater) than about 100 days are predominantly barotropic (baroclinic), unlike the near-field, eddy-generating, free-jet region which contains barotropic and baroclinic energy throughout the modei frequency range. The far-field barotropic energy produces a peak in the model sea-level spectra between 25 and 50 days with a magnitude comparable to energy levels observed in spectra of sea level from oceanic island tide gauges. The far-field barotropic motion is clearly composed of large-scale, resonant, barotropic normal modes drive by mesoscale activity of the turbulent, free-jet region. Oceanic mesoscale turbulence may therefore provide for planetary normal modes an excitation mechanism distinct from atmospheric forcing. The open-ocean, barotropic, model response is very similar to that of a fluctuating-wind driven model, which suggests that atmospheric and intrinsic forcing of mid-ocean eddies may be of comparable importance. |
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| Keywords: | Ocean Circulation mesoscale currents quasigeostrophic flows Rossby waves |
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