Gyre circulation

That is, the radiotracer length scale exceeds the gyre scale, which means that the putative stream mbe folds back on itself within the gyre circulation, short-circuiting the advective-diffusive balance, and lowering the effective Peclet number of the flow. 

In the subtropics, where wind-stress is convergent, water tends to be forced downward from the surface ocean into the thermocline. This downwelling is an important process for ventilation of the thermocline, and for driving the shallow gyre circulation. Figure 8 shows the measured tritium-helium age as measured... 

Figure 4 Tracer results from a two-dimensional gyre model. The model represents the circulation on a constant density surface (isopycnal) in the main thermocline that outcrops along the northern boundary (shaded region). Thermocline ventilation is indicated by the gradual increase of tritium- He ages around the clockwise flowing gyre circulation. TU, tritium unit (1 TU = 1 atom/10 H...

As a result of these factors (wind, Ekman transport, Coriolis force) the surface ocean circulation in the mid-latitudes is characterized by clockwise gyres in the northern hemisphere and the counterclockwise gyres in the southern hemisphere. The main surface currents around these gyres for the world s oceans are shown in Fig. 10-6. The regions where Ekman transport tends to push water together are called convergences. Divergences result when surface waters are pushed apart. 

Fig. 1 General circulation schema in the Black Sea upper layer (0-500 m) 1 annual mean climatic isohalines (psu) at a depth of 100 m, 2 1000 m depth contour, 3 bifurcation branch of the Rim Current, 4 quasi-stationary eddies, 5 non-stationary eddies and subbasin gyres, 6 non-stationary coastal vortices. The areas shallower than 100 m are shaded...

The seasonal variability of the horizontal structure of the main pycno cline is well manifested in the salinity field at the 100-m level (Fig. 8). In all the seasons of the year, three types of structural elements are recognized the alongshore MFZ, the central areas of the salinity maximums, and the nearshore areas of the salinity minimums. Each of them is closely related to the corresponding elements of the general water circulation in the upper 500-m layer of the Black Sea [34], such as the BSRC, the central cyclonic gyres, and the QSNSAG [21]. 

Jenkins W. J. (1988) Using anthropogenic tritium and 3He to study subtropical gyre ventilation and circulation. Phil. Trans. Roy. Soc. London A325, 43-61. 

The notion of the predesiccation Aral Sea circulation is somewhat speculative, given that extremely few (if any) direct current measurements have been reported. However, already the early researchers [7, 8] perceived the most peculiar feature of the sea s basin-scale circulation, namely, its anticyclonic direction (although there was also a hint of a smaller cyclonic gyre north of Barsakelmes Island [4, 9]). As is well known, the neighboring enclosed seas lying in the same latitude belt, such as the Black Sea, the Sea of Azov, and the Caspian Sea, all exhibit cyclonic... 

Fig. 6.1 Major features of surface circulation in the NW Indian Ocean during (a) Northeast monsoon, and (b) Southwest monsoon (EACC - East African Coast Current SECC - South Equatorial Countercurrent SC - Somali Current WICC - West Indian Coast Current NMC - Northeast Monsoon Current LH - Lakshadweep High SG - Southern Gyre GW - Great Whirl SE - Socotra Eddy RHJ -Ras-al-Hadd Jet LL - Lakshadweep Low SMC - Southwest Monsoon Current). Redrawn from Schott and McCreary (2001) with permission from Elsevier Science.

Two dimensional gyre-scale tracer models have been fruitfully applied to observed isopycnal tri-tium- He and chlorofluorocarbon patterns. As shown in Figure 4, recently ventilated water (nearzero tracer age) enters the thermocline on the pole-ward side of the gyre and is swept around the clockwise circulation of the gyre (for a Northern Hemisphere case). Comparisons of model tracer patterns and property-property relationships constrain the absolute ventilation rate and the relative effects of isopycnal advection versus turbulent mixing by depth and region. 

The basic circulation pattern of the South China Sea is as follows there are two cyclonic eddies, one located east of Vietnam and the other off northwest Luzon, occurring in the upper layer of the SCS (Fig. 1.39, Liu QY et al., 2008). The structure of the upper layer circulation in the SCS depends on the relative importance of these two eddies. In winter both eddies are developed and there is a generally cyclonic gyre over the entire deep basin of the SCS, while during... 

When large-scale circulation is concerned, the northeast monsoon will drive a basin-scale cyclonic circulation with each cyclonic g rre in the northern and southern SCS (NSCS, SSCS), respectively, and the circulation displays a double-g3Te structure. In summer, the circulation in the NSCS will still maintain a weak cyclonic gyre. However, due to the southwest monsoon, the circulation in the SSCS displays an anticyclonic g3Te. 

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