Geostrophic

When the isobars are essentially straight, the balance between the pressure gradient force and the coriolis force results in a geostrophic wind parallel to the isobars. 

This describes the geostrophic wind f- 2co sin 4>, where oj is the angular velocity due to the rotation of the Earth and 0 is the latitude). The air moves parallel to the isobars (lines of constant pressure). The geostrophic wind blows counterclockwise around low-pressure systems in the northern hemisphere, clockwise in the southern. 

X 10 Pa/m), P 15m/s. In many instances, the observed wind is indeed close to the geostrophic wind and it is often useful to have maps of isobars so thaf the transport trajectory can be approximated from Vg. For a complete derivation and explanation of the geostrophic wind, departures from it and related topics, the reader is referred to textbooks on meteorology (e.g., Wallace and Hobbs, 1977). 

For typical meteorological conditions the maximum diffusivity can be expected to be in the range 0.5-5 m sec". The magnitude is considerably smaller than the equivalent values encountered under strongly unstable conditions. A limitation of the above formulation is the need for knowledge of the geostrophic wind velocity Vg. If the assumption Vg == 8m., discussed in the previous section, is employed, then Eq. (9.25) can be written in the form... 

In the open ocean, the major advective water motion is associated with the surfece-water geostrophic currents and meridional overturning circulation. These flow paths are shown in Figures 4.4b and 4.6. Advection is much fester than molecular diffusion and turbulence. This enables water masses to retain their original temperatures and salinities as they are advected away from their sites of formation. Slow turbulent mixing with adjacent water masses eventually alters this temperatme and salinity signal beyond... 

NADW flows south from its site of formation until it reaches the Southern Ocean where it joins up with AABW The water masses then flow eastward under the influence of the Westerlies. A branch heads off into the Indian Ocean and the rest enters the South Pacific. All along these flow paths, upward advection and turbulent mixing slowly return the water to the surface where the geostrophic currents eventually carry it back to the Atlantic Ocean. Because a major feature of the flow paths is transport across latitudes. 

The abyssal clays are composed primarily of clay-sized clay minerals, quartz, and feldspar transported to the siuface ocean by aeolian transport. Since the winds that pick up these terrigenous particles travel in latitudinal bands (i.e., the Trades, Westerlies, and Polar Easterlies), the clays can be transported out over the ocean. When the winds weaken, the particles fell to the sea siufece and eventually settle to the seafloor. Since the particles are small, they can take thousands of years to reach the seafloor. A minor fraction of the abyssal clays are of riverine origin, carried seaward by geostrophic currents. Despite slow sedimentation rates (millimeters per thousand years), clay minerals, feldspar, and quartz are the dominant particles composing the surface sediments of the abyssal plains that lie below the CCD. Since a sediment must contain at least 70% by mass lithogenous particles to be classified as an abyssal clay, lithogenous particles can still be the major particle type in a biogenous ooze. 

Geostrophic current The advection of water resulting from the balance between gravity, wind stress, and the Coriolis Effect. 

Gyres A set of four interlocking geostrophic currents that move water in each ocean basin. Northern hemisphere gyres move surface waters clockwise, while southern hemisphere gyres move water counterclockwise. 

The estimates of the climatic mean annual parameters of the MRC in the sections normal to the northeastern coast of the Black Sea presented in [17] yielded a distance of its core from the shore about 40 km, a full width of the current (with respect to velocity values of 0.02 m s-1) of 75 km, a penetration depth of 275 m, a maximal geostrophic velocity of 0.31 ms-1, and a volume transport of 1.3 x 106 m3 s x. These estimates are of the same order of magnitude as shown in Fig. 4a within the velocity interval to 0.20 m s x. This allows us to suggest a certain geographical universality (self-similarity) of the MRC profile normal to the coast. 

In July 1992, off the Turkish coast, a slightly meandering MRC stream was observed its core was approximately 30 km wide and had maximal velocities in the upper layer 50-75 m thick up to 0.50 ms-1 [22], In the layer from 75 to 125 m, the most rapid velocity drop was observed (by 0.25 ms-1). At a depth of 200 m, the values decreased down to 0.05-0.10 m s-1. Toward the coast, the velocities decreased by 0.20 m s 1 per 10 km, the rate of their decrease in the seaward direction was fourfold lower. The maximal geostrophic velocities with respect to the 500-dbar level were 0.20 ms-1 lower than the ADCP velocities, which points to significant ageostrophic effects in the MRC dynamics. 

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