A subgrid-scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non-eddy-resolving ocean circulation models. The mixing is applied in isopycnal coordinates to isopycnal ...layer thickness, or inverse density gradient, as well as to passive scalars, temperature and salinity. The transformation of these mixing forms to physical coordinates is also presented.
Horizontal momentum flux in a global ocean climate model is formulated as an anisotropic viscosity with two spatially varying coefficients. This friction can be made purely dissipative, does not ...produce unphysical torques, and satisfies the symmetry conditions required of the Reynolds stress tensor.
This paper describes the global ocean component of the NCAR Climate System Model. New parameterizations of the effects of mesoscale eddies and of the upper-ocean boundary layer are included. ...Numerical improvements include a third-order upwind advection scheme and elimination of the artificial North Pole island in the original MOM 1.1 code. Updated forcing fields are used to drive the ocean-alone solution, which is integrated long enough so that it is in equilibrium. The ocean transports and potential temperature and salinity distributions are compared with observations. The solution sensitivity to the freshwater forcing distribution is highlighted, and the sensitivity to resolution is also briefly discussed.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Changes in the ventilation rate of the global ocean during the 20th and 21st centuries, as indicated by changes in the distribution of ideal age, are examined in a series of integrations of the ...Community Climate System Model version 3. The global mean age changes little in the 20th Century relative to pre-industrial conditions, but increases in the 21st Century, by an amount that is independent of the range of climate forcings considered. The increase is primarily due to a decrease in the ventilation rate of Antarctic Bottom Water (AABW), and to a lesser degree, North Atlantic Deep Water (NADW). Changes in a regional volumetric census of age indicate that the changes in AABW are predominantly for waters that are already older than 100
years, so will likely have a moderate direct feedback on oceanic uptake of CO
2 and other tracers. On the other hand, the changes in NADW occur most strongly in waters that are a few decades old, so are more likely to have a feedback on the climate system. While the global mean age increases, the age does not increase everywhere in the ocean. Regions newly exposed to strong atmospheric forcing as sea ice retreats experience an increase in convection and decreasing age. Age also decreases over a large volume of the lower thermocline as the rate of upwelling of old deep water decreases with the weakening of the thermohaline circulation.
The response of a rectangular, flat-bottom, eddy-resolving, quasigeostrophic ocean to a steady, double-gyre wind stress is studied to assess the sensitivity of the solutions to a partial-slip lateral ...boundary condition in which tangential stress is proportional to tangential velocity. The constant of proportionality ( alpha ) has limiting values of zero and infinity, corresponding to free-slip (no-stress) and no-slip conditions, respectively. Significant qualitative changes in the time-mean behavior of the solutions are observed to occur with increasing alpha . These changes include a gradual retreat of the separation points of the western boundary currents in the subtropical and subpolar gyres, a dramatic reduction in the basin-integrated reservoirs of mean and eddy kinetic energy, a weakening of bottom dissipation and its replacement by lateral dissipation as the dominant sink of kinetic energy, and the emergence of secondary pools of homogenized potential vorticity within the interiors of the time-mean gyres. Similar dependencies on alpha are found to apply across a broad dynamical regime encompassing alternate type and strengths of lateral friction, asymmetric wind forcing, and dynamically more complete governing equations.
The shallow-water equations (SWE), which are used very frequently as an analogue of atmospheric and oceanic flows governed by the primitive equations (PRE), are examined. The SWE are energetically ...inconsistent compared to the PRE.
The annual mean heat budget of the TOGA‐COARE domain is examined in a reduced‐gravity, primitive equation model of the upper equatorial ocean that is described by Gent and Cane (1989). It is forced ...by the monthly winds from Rasmusson and Carpenter (1982), and the heat flux formulation is from Seager et al. (1988). It is concluded that the annual mean net heating of the ocean surface in the area 140°E‐180°E, 10°S‐10°N is between 0 and 20 W m−2. This is considerably less than the estimates given in climatic atlases which vary from about 30 W m−2 (Esbensen and Kushnir, 1981; Hsiung, 1985), about 50 W m−2 (Weare et al., 1981), to about 70 W m−2 (Reed, 1985). These estimates have no physical constraints on the analysis, whereas the model result is constrained by the ocean's ability to remove heat from the TOGA‐COARE domain.
Different parameterizations for vertical mixing and the effects of ocean mesoscale eddies are tested in an eddy-permitting ocean model. It has a horizontal resolution averaging about 0.7° and was ...used as the ocean component of the parallel climate model. The old ocean parameterizations used in that coupled model were replaced by the newer parameterizations used in the climate system model. Both ocean-alone and fully coupled integrations were run for at least 100 years. The results clearly show that the drifts in the upper-ocean temperature profile using the old parameterizations are substantially reduced in both sets of integrations using the newer parameterizations. The sea-ice distribution in the fully coupled integration using the newer ocean parameterizations is also improved. However, the sea-ice distribution is sensitive to both sea-ice parameterizations and the atmospheric forcing, in addition to being dependent on the ocean simulation. The newer ocean parameterizations have been shown to improve considerably the solutions in non-eddy-resolving configurations, such as in the climate system model, where the horizontal resolution of the ocean component is about 2°. The work presented here is a clear demonstration that the improvements continue into the eddy-permitting regime, where the ocean component has an average horizontal resolution of less than 1°.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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