Boundary current

Abstract: Given that middle latitude weather systems transport heat in a manner such as to weaken the baroclinicity that is thought to be crucial to their growth, it is perhaps surprising that concentrated regions of such eddy activity, i.e. storm-tracks, are found in the Northern Hemisphere winter. The existence and possible self-maintenance of storm-tracks is investigated using a linear, stationary wave model with storm-track region forcings taken from data averaged over a number of winters. It is found that the direct thermal effect of the eddies does indeed act against the existence of the storm-track. Their vorticity fluxes lead to some reduction of this effect. It is argued that the mean diabatic heating in the storm-track region is an indirect eddy effect. This heating is found to maintain the mean maximum in baroclinicity in the region. Further, the mean low-level flow induced by the eddy effects is such as to enhance the warm western oceanic boundary currents that are crucial to the existence of t...

Abstract: I have used the patterns of tracers (temperature, salinity, oxygen, silica, helium-3) and of density to estimate the geostrophic circulation (baroclinic plus barotropic) of the South Pacific Ocean at all depths. That is, the direction of horizontal flow is determined at all depths in a manner that appears to be consonant with the tracer patterns and that satisfies continuity of mass. Within the upper kilometer the velocity shear is much stronger than at greater depths, and the baroclinic flow field alone is closely consonant with the tracer patterns except near the western boundaries. The barotropic components added to the baroclinic to provide a flow field that matches the tracer patterns in the deeper waters and to achieve continuity are quite small except in the western boundary currents, and only there do they provide a combined flow pattern significantly different from the baroclinic alone. The resulting field of flow has equatorward deep western boundary undercurrents in each of the three basins and a poleward flow along the eastern boundary. A part of the Circumpolar Current follows the southern side of the East Pacific Rise around the Southeast Pacific Basin and then through the Drake Passage. The broad-ocean anticyclonic gyre of the upper waters is broken at depth by the Tonga-Kermadec Ridge and the East Pacific Rise into separate gyres in the Tasman Sea and the central basin, where it extends nearly to the bottom in the north. In the central basin the northward abyssal flow is not confined to the western boundary but extends all across the basin, diverted only slightly in the north by the small deep remnant of the anticyclonic gyre.

Abstract: A decade-mean global ocean circulation is estimated using inverse techniques, incorporating air–sea fluxes of heat and freshwater, recent hydrographic sections, and direct current measurements This information is used to determine mass, heat, freshwater, and other chemical transports, and to constrain boundary currents and dense overflows The 18 boxes defined by these sections are divided into 45 isopycnal (neutral density) layers Diapycnal transfers within the boxes are allowed, representing advective fluxes and mixing processes Air–sea fluxes at the surface produce transfers between outcropping layers The model obtains a global overturning circulation consistent with the various observations, revealing two global-scale meridional circulation cells: an upper cell, with sinking in the Arctic and subarctic regions and upwelling in the Southern Ocean, and a lower cell, with sinking around the Antarctic continent and abyssal upwelling mainly below the crests of the major bathymetric ridges