2 Factors that Influence Ocean Currents Ocean currents are masses of ocean water that flow from one place to anothersurface currents develop from friction between the ocean and the wind that blows across its surfacesome currents are short- lived and affect only small areasthese are a response to local/seasonal influencesother currents are relatively permanent that extend over long areas of the oceansthe major horizontal movements of surface water is closely related to the general circulation pattern of the atmosphere
3 Ocean Circulation Patterns Gyre = the large circular surface current pattern found in each oceaneg, North Pacific Gyrethe center of each gyre coincides with the subtopics at about 30 degrees North or South latitude, so they are often called subtropical gyresthere is a correspondence between the direction of surface- current flow and the major wind belts of the worldsubtropical gyres rotate clockwise in the Northern Hemisphere, and counterclockwise in the Southern Hemispherethis is because wind generates surface currents, as well as...the Coriolis Effectthe deflective force of Earth's rotation on all free- moving objects, including the atmosphere and oceansthere are four main currents within each gyreif an object is dropped into a gyre it would take about six years to go completely aroundwhen the North Atlantic Current goes towards Western Europe, it splits and carries warm weather to the otherwise cold area
5 More Ocean Circulation Patterns the circular motion of gyres leaves a large central area that has no well-defined currentsin the North Atlantic, this zone of calmer waters is known as the Sargasso Sea, named for large amounts of Sargassum, a type of floating seaweedIndian Ocean is influenced by summer and winter monsoonswhen the winds change direction, the surface currents also change direction
7 Ocean currents Ocean currents Warm currents- move from low to high latitudes (move heat from warmer to cooler areas)North American current keeps Great Britain and western Europe warmer than would be expected based on their latitudeCold currents- move from high to low latitudes( moderate temperatures in tropics and mid-latitudes)Benguela Current (western Africa), Peru Current, California CurrentCause fogs and droughts/deserts along the west coast of continents ( Atacama, Namib)Maintain Earth’s heat balance- ¼ heat transported from tropics to poles is transported by water, the rest is by wind
8 Peru Current"GS103 - Lecture Outlines Sp08." GS103 - Lecture Outlines Sp08. Web. 22 May <http://nsm1.nsm.iup.edu/hovan/classes/GEOS103_OL_sp08.html>.
9 UpwellingUpwelling is the rising of cold water from layers below the surface.Induced by windBrings nutrient rich water to the surfaceSupports marine organismsMost common on west coastsMost distinguished: California, Western South America, and West AfricaCause of upwellingCoastal winds and Coriolis effect cause surface water to move away from the shore
10 Upwelling Cause of upwelling Cold water from below replaces warmer surface waterResults in lower surface temperaturesFor example, Atlantic temperatures in August are 21°C or higher and Pacific temperatures are 15°C
11 Deep-ocean Circulation Deep ocean Circulation is governed by gravity and driven by density differences- Density differences are caused by temperature and salinity differences. Because of this Deep-ocean circulation is often also called thermohaline circulation.-Density differences cause denser water to sink and slowly spread out beneath the surface
12 Deep-Ocean Circulation Deep-ocean currents-Deep-ocean currents are created when the water involved with thermohaline circulation begins in high latitudes at the surface and then sinks.-The water at high latitudes was there because the salinity, the amount of salt in the water, of the cold water increased due to sea-ice formation.
14 Various Components of the Coastal Zone Shorelines Are Dynamic-topographygeologic makeupclimateShore- area that extends between the lowest tide level and the highest elevation on land that is affected by storm wavesShore is divided into two parts-Foreshore-area exposed when the tide is out and submerged when the tides inBackshore-landward of the high tide shoreline. Usually dry, being affected by waves only during stormsTwo other zones-Nearshore Zone-lies between the low tide shoreline and the line where waves break at low tideOffshore Zone-seaward of the nearshoreShoreline- line that marks the contact between land and sea
15 Various Components of the Coastal Zone Coast-extends inland from the shore as far as ocean related features can be foundCoastline-marks the coast's seaward edge, whereas the inland boundary is not always obvious or easy to determine