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Ocean Circulation. Currents. Currents. Horizontally Vertically. The Forces That Drive Currents. Primary forces Starts water movement and determine its velocity Stress of wind Secondary forces Influence the direction and nature of flow Coriolis effect gravity friction
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Ocean Circulation Currents
Currents • Horizontally • Vertically
The Forces That Drive Currents • Primary forces • Starts water movement and determine its velocity • Stress of wind • Secondary forces • Influence the direction and nature of flow • Coriolis effect • gravity • friction • shape of ocean basins
Surface currents • Wind • Surface currents • rapid with well defined boundaries • slow and diffuse • horizontal or vertical • Gyre
Bottom Currents • Driven by the force of gravity - dense water sinks and less dense water rises
Flow within a Gyre • North Atlantic gyre • Four inter connected currents
Eckman spiral • Eckman transport
Geostrophic Gyres • Geostrophic Gyre • 5 Geostrophic gyre • North Atlantic gyre • South Atlantic gyre • North Pacific gyre • South Pacific gyre • Indian Ocean gyre • Geostrophic gyres independent of each other in each hemisphere • Geostrophic currents • 6 current circuits in the world ocean • 2 in Northern hemisphere 4 in southern hemisphere
Currents within Gyres • Western boundary Currents • Eastern Boundary Currents • Transverse currents
Western Boundary Currents • Fastest and deepest • Found at the western boundaries of the Ocean basins • Narrow • Move warm water poleward in each gyre
Western boundary currents • Five western boundary currents • Gulf stream • Japan or Kuroshio current • Brazil current • Agulhas current • East Australian current • Sverdrup • Eddies • Cold core eddies • Warm core eddies
Eastern Boundary Currents • The Canary Current • The Benguela Current • California Current • West Australian Current • The Peru or Humboldt Current
Eastern Boundary Currents • Carry cold water equatorward • Shallow and broad • Boundaries not well defined • Eddies tend not to form
Westward Intensification • The converging flow of the trade winds on either side of equator • The rotation of the earth
Transverse Currents • Currents that flow from east to west • Linking the eastern and western boundary currents • Counter Currents • Under Currents
Exceptional Surface Currents • Monsoon Currents • High Latitude Currents
Effects of Surface Currents on Climate • Distribute tropical heat • Influences climate and weather
Wind-Induced Vertical Circulation • Upwelling • Equatorial upwelling • Coastal upwelling • Downwelling
Langmuir Circulation (page 222 fig 9.16) • Langmuir Circulation
Thermohaline Circulation • Density driven
Water Masses • Five common water masses • Surface water • Central water • Intermediate water • Deep water • Bottom water
Formation and downwelling of Deep water • Antarctic bottom water • North Atlantic deep water
Thermohaline Circulation Patterns • Low and mid latitudes • Caballing • Contour currents
Studying Currents • Float method • Flow method • Acoustical Tomography