Ocean Circulation 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

El Nino

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