Ch.5 - Ch. 5 The Circulation of Oceans Review Ch. 4: oceans...

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Ch. 5 The Circulation of Oceans Review Ch. 4: oceans are vertically stratified, denser at bottoms of ocean basins and less- dense near the surface. Density is controlled by the temp. and by salt/salinity of the water. Winds and Surface Currents Solar heating of the ocean takes place at upper surface of the fluid, whereas the solar heating of atmosphere occurs at lower surface of fluid near Earth’s surface Solar heating= warmer water at the surface of most of the world’s ocean Movement of wind over the ocean causes friction at surface friction drags ocean surface with it as it blows, surface ocean wind drift currents o Wind stress force of wind acting on the surface o Trade winds o Coriolis effect influences winds, water is deflected to right of the path of wind in the N. Hemisphere, and to left of wind’s path in S. Hemisphere Trade winds produce westward flowing currents in the tropics, when these currents reach western continental boundary, they are deflected northward and southward Influenced by westerlies, causing currents to flow eastward in the midlatitudes The waters that flow toard the poles as replaced by equatorward flow along the western landmass Water that flows toward equator come back under influence of trade winds and blown westward again o Gyre circular circulation pattern in subtropical oceans, completed by large currents o in S. Hemisphere, westerlies result in an eastward flowing current—the west wind drift— that extends around the globe Convergence o Water piles up/converges in the middle of the gyre Results from combined effects of the wind-driven surface ocean currents, Earth’s rotation, and friction o Ekman spiral deeper below the surface, the farther each layer is deflected to the right or left of the surface layer, producing a spiraling effect known as this Ekmins theory: under strong and persisten winds in the open ocean… 1. Surface current will flow at 45degrees to the surface-wind path 2. Flow will be reversed at approx. 100m below the surface 3. Also be considerably reduced in speed Ekman Transport: when the movements of all the individual layers of water in the spiral are added, the net direction of transport within the water column is at a right angle to the wind direction
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Divergence Occurs near the equator, can also be found at coast lines with convergence where Ekman transport may push water toward or away from the coast, depending on direction of wind movement and surface current Upwelling/ downwelling Convergence: surface water piles up, sea surface rises, and surface layer of water thickens Divergence: surface water moves away, sea surface drops, and surface layer thins o Downwelling: where convergence occurs, accumulation of water causes it to
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Ch.5 - Ch. 5 The Circulation of Oceans Review Ch. 4: oceans...

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