Open-ocean response and normal mode excitation in an eddy-resolving general circulation model

OI.R 11987) 34 (9)

A, Physical Oceanography

velocity field during the 1982-83 event. The thickness of the equatorial 13°C water thermostad is examined and compared to earlier measurements, and local estimates of the zonal slope of the dynamic height along the Equator are presented and compared with the vertical profiles of zonal current. PMEL, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115, USA. 87:4876 Piola, A.R. and A.L. Gordon, 1986. On oceanic heat and freshwater fluxes at 30°S. J. phys. Oceanogr., 16(12):2184-2190. A simple box model based on mass, heat and salinity conservation combined with existing estimates of ocean-atmosphere heat and freshwater exchanges is used to calculate the oceanic mean meridional volume fluxes of three water masses at 30°S. Model results lead to relatively large volume fluxes and questionable flow directions in the South Pacific. It is shown that although solutions are sensitive to changes in the mean temperature and salinity of each water mass, changes of these properties within realistic limits cannot lead to large changes in the mass fluxes or flow reversals. The effect of changes in the ocean-atmosphere fluxes north of 30°S on the oceanic mass transports is evaluated. Servicio de Hidrografia Naval, Buenos Aires, Argentina.

A80. Circulation 87:4877 Killworth, P.D., 1986. A Bernoulli inverse method for determining the ocean circulation. J. phys. Oceanogr., 16(I 2): 2031-2051. A new inverse method for finding the large-scale ocean circulation is described which uses no horizontal gradient information, and is designed for widely spaced data. The requirement that Bernoulli functions should match at points where density and potential vorticity match leads to a heavily overdetermined problem for the surface pressure field, solved by a singular-value decomposition. Analysis shows that for closely spaced data, the Bernoulli method reduces to beta-spiral dynamics, but with additional constraints from nonneighboring stations. The method, essentially nonlocal in character as it depends on following flow streamlines, seems to be fairly robust both to noise in the data and to station spacing and selection. Hooke Inst. for Atmos. Res., Clarendon Lab., Oxford OX1 3PU, UK.

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87:4878 Kundu, P.K. and J.P. McCreary Jr., 1986. On the dynamics of the throughflow from the Pacific into the Indian Ocean. J. phys. Oceanogr., 16(12): 2191-2198. The circulation forced by an inflow of water through an eastern ocean boundary is investigated using two linear, viscid, and continuously stratified models. One of the models has a flat bottom, and solutions are obtained analytically; the other has a continental shelf, and solutions are found numerically. Without vertical mixing all the inflow continues across the ocean. With vertical mixing, however, part of it bends poleward to generate a coastal circulation. The presence of a shelf displaces the coastal currents offshore, but otherwise changes their structure and magnitude very little. Solutions suggest that the southward bending of the throughflow from the Pacific into the Indian Ocean may contribute to the Leeuwin Current off western Australia, but that it is not the dominant mechanism for driving the circulation there. Oceanogr. Center, Nova Univ., Dania, FL 33004, USA. 87:4879 Miller, A.J., W.R. Holland and M.C. Hendershott, 1987. Open-ocean response and normal mode excitation in an eddy-resolving general circulation model. Geophys. astrophys. Fluid Dynam., 37(4): 253-278. A two-layer, flat-bottom, steady-wind driven, eddyresolving GCM 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 ~ 100 days are predominantly barotropic (baroclinic), unlike the near-field, eddy-generating, free-jet region which contains barotropic and baroclinic energy throughout the model frequency range. The far-field barotropic energy produces a peak in the model sea-level spectra between 25 and 50 days. The far-field barotropic motion is clearly composed of large-scale, resonant, barotropic normal modes driven by mesoscale activity of the turbulent, free-jet region. Scripps Inst. of Oceanogr., IGPP A-025, La Jolla, CA 92093, USA. 87:4880 Wajsowicz, R.C. and A.E. Gill, 1986. Adjustment of the ocean under buoyancy forces. Part I. The role of Kelvin waves. J. phys. Oceanogr., 16(12): 2097-2114. The early stages of the adjustment of an ocean toward equilibrium is examined using an ocean general circulation model. The initial state is one