1,720,975 research outputs found
Modeling the global circulation response and the regional response of the Arctic Ocean to the external forcing anomalies
No full textThe problem of numerical modeling and analysis of the large-scale World Ocean circulation variability under variations of the external forcing is considered. A numerical model was developed in the INM RAS and is based on the primitive equations of the ocean circulation written in a spherical generalized ?-coordinate system. The model's equations are approximated on a grid with resolution of 2.5° × 2° × 33, and the North Pole is displaced to the continental point (60°E, 60.5°N). There are two stages for the numerical experiments. The quasi-equilibrium circulation of the World Ocean under the climatological atmospheric forcing is simulated at the first stage. The run is carried out over a period of 3000 years during which a quasi-equilibrium model regime is formed. At the second stage, the sensitivity of the model ocean circulation to the atmospheric forcing perturbations in the Southern Hemisphere is studied. According to the results, the strongest regional changes in the hydrography take place in the Arctic Ocean. Substantial changes of sea's surface height and local anomalies of the temperature and salinity are formed there
Comparison of N. Atlantic heat storage estimates during the Argo period (1999–2010)
No full textOcean heat storage is an essential component of the climate system and there is considerable interest in its accurate evaluation. There are a number of heat storage products produced by many different groups. These products are derived from Argo as well as other platforms, for example XBT and CTD, in the last decade. Here we compare two heat storage estimates for the North Atlantic 0–2000 m from 10° to 70° N. One derived solely from Argo data whilst the other is derived from Argo and other platforms. It is found that there is a positive trend in heat storage over the period 1999–2010. This trend is influenced by a strong air–sea interaction event in 2009–2010, and this reduces the upward trend 1999–2008 identified previously. Both data sets are consistent with each other for the layer 0–1000 m on a timescale of beyond 1 yr. There are significant differences at sub-annual time scales and in the layer 1000–2000 m
Vladimir Kamenkovich – Scientist and Teacher
Full text linkThis special collection of articles is dedicated to Vladimir Kamenkovich, on the occasion of his 80th birthday. We take this opportunity to celebrate his extraordinary career in science and education. Through his pioneering work, Vladimir Kamenkovich has made important contributions to the development of modern physical oceanography, being, in the words of Peter Rhines, “a great force in ocean dynamics,” and he has inspired many scientists worldwide. It is fair to say that the field of ocean dynamics would have been very different if Vladimir had chosen a different career path
Can the equatorial ocean quickly respond to Antarctic sea ice/salinity anomalies?
No full textEl Niño Southern Oscillation (ENSO) plays a critical role in many of the extremes or anomalies of climate, causing floods, droughts and the collapse of fisheries. Recent studies have revealed a statistically–significant link between equatorial processes and sea-ice anomalies in the Southern Ocean. The generally accepted view is that the primary interaction of the equatorial and polar oceans takes place via the atmosphere. Indeed, the lag in these processes is usually of the order of a few months, and is much too quick to be connected with ocean currents. The question is: can climate anomaly signals effectively and rapidly propagate by another oceanic mechanism? It is demonstrated that signals generated by anomalies in the Antarctic sea-ice cover/salinity distribution can propagate in a wave-like manner in the form of fast-moving barotropic Rossby waves. Such waves propagates from the Drake Passage to the western Pacific in only few days. This signal is reflected at the western boundary of the Pacific and generates an coastally trapped Kelvin wave moving equatorwards. The resulting temperature anomaly propagates northwards along the western coastline to the vicinity of the equator and increases in amplitude in time. The anomaly in the western edge of the equatorial Pacific then begins to move eastward along the equator as a trapped equatorial wave. After about 2–3 months this wave reaches the eastern coast. This process is suggested as one possible direct mechanism by which the extra–tropical ocean can induce anomalies in the equatorial ocean. <br/
On the meridional circulation and balance of momentum in the Southern Ocean of POP
No full textpThe circulation of the Southern Ocean is studied in the eddy-resolving model POP (Parallel Ocean Program) by an analysis of zonally integrated balances. The TEM formalism (Transformed Eulerian Mean) is extended to include topography and continental boundaries, thus deviations from a zonally integrated state involve transient and standing eddies. The meridional circulation is presented in terms of the Eulerian, eddy-induced, and residual streamfunctions. It is shown that the splitting of the meridional circulation into Ekman and geostrophic transports and the component induced by subgrid and Reynolds stresses is identical to a particular form of the zonally integrated balance of zonal momentum. In this balance, the eddy-induced streamfunctions represent the interfacial form stresses by transient and standing eddies and the residual streamfunction represents the acceleration of the zonal current by density fluxes in a zonally integrated frame. The latter acceleration term is directly related to the surface flux of density and interior fluxes due to the resolved and unresolved eddies. The eddy-induced circulation is extremely vigorous in POP. In the upper ocean a shallow circulation, reversed in comparison to the Deacon cell and mainly due to standing eddies, appears to the north of Drake Passage latitudes, and in the Drake Passage belt of latitudes a deep-reaching cell is induced by transient eddies. In the resulting residual circulation the Deacon cell is largely cancelled and the residual advection of the zonal mean potential density is balanced by diapycnal eddy and subgrid fluxes which are strong in the upper few hundred meters but small in the ocean interior. The balance of zonal momentum is consistent with other eddy-resolving models; a new aspect is the clear identification of density effects in the zonally integrated balance. We show that the wind stress and the stress induced by the residual circulation drive the eastward current, whereas both eddy species result in a braking. Finally, we extend the Johnson–Bryden model of zonal transport to incorporate all relevant terms from the zonal momentum balance. It is shown that wind stress and induction by the residual circulation carry an eastward transport while bottom form stress and the stress induced by standing eddies yield westward components of transport
Influence of bottom topography on integral constraints in zonal flows with parameterized potential vorticity fluxes
Full text linkAn integral constraint for eddy fluxes of potential vorticity (PV), corresponding to global momentum conservation, is applied to two-layer zonal quasi-geostrophic channel flow. This constraint must be satisfied for any type of parameterization of eddy PV fluxes. Bottom topography strongly influence the integral constraint compared to a flat bottom channel. An analytical solution for the mean flow solution has been found by using asymptotic expansion in a small parameter which is the ratio of the Rossby radius to the meridional extent of the channel. Applying the integral constraint to this solution, one can find restrictions for eddy PV transfer coefficients which relate the eddy fluxes of PV to the mean flow. These restrictions strongly deviate from restrictions for the channel with flat bottom topography
Numerical model of the Baltic Sea circulation
No full textThe problem of numerical simulation of the Baltic Sea large-scale circulation is considered. The Baltic Sea numerical model is based on the two previous models: the model of ocean dynamics developed at the Institute of Numerical Mathematics of the RAS and the FRESCO model of marine hydroecosystem developed at the Estonian Marine Institute, University of Tartu. The model is based on primitive equations written in spherical ? coordinates with a free surface in the hydrostatic and Boussinesq approximations. The structure of numerical algorithm is described. The algorithm is based on the method of multicomponent splitting and includes splitting by physical processes and spatial coordinates. The equations of sea dynamics are written in a symmetrized form. The problem is split into several energetically balanced subsystems (splitting by physical processes). Each subsystem can be additionally split into subsystems of a simpler structure (splitting by spatial coordinates). The numerical experiment consists in the calculation of the Baltic Sea hydrodynamic fields with the spatial horizontal resolution of ~3.5 km and 25 vertical ?-levels nonuniformly distributed over the depth. The atmospheric forcing is calculated according to the Era-Interim data, the calculation period is 2 years: 2007 and 2008. The results of numerical simulation demonstrate good resemblance to observation data, as well as the results of the Baltic Sea dynamics computation obtained from other models
Is the coefficient of eddy potential vorticity diffusion positive? Part1: barotropic zonal channel.
Full text linkThe question of whether the coefficient of diffusivity of potential vorticity by mesoscale eddies is positive is studied for a zonally reentrant barotropic channel using the quasi-geostrophic approach. The topography is limited to the first mode in the meridional direction but is unlimited in the zonal direction. We derive an analytic solution for the stationary (time-independent) solution. New terms associated with parameterized eddy fluxes of po-tential vorticity appear both in the equations for the mean zonal momentum balance, and the kinetic energy balance. These terms are linked with the topographic form stress exerted by parameterized eddies. It is demonstrated that in regimes with zonal flow (analogous to the Antarctic Circumpolar Current), the coefficient of eddy potential vorticity diffusivity must be positive
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