Chapter 15Section - 1

• Ocean currents are masses of ocean water that flow from one place to another

• surface currents develop from friction between the ocean and the wind that blows across its surfaceo some currents are short- lived and affect

only small areas these are a response to local/seasonal

influenceso other currents are relatively permanent

that extend over long areas of the oceans• the major horizontal movements of surface water is

closely related to the general circulation pattern of the atmosphere

Factors that Influence Ocean Currents

Ocean Circulation Patterns

• the circular motion of gyres leaves a large central area that has no well-defined currentso in the North Atlantic, this zone of calmer

waters is known as the Sargasso Sea, named for large amounts of Sargassum, a type of floating seaweed

• Indian Ocean is influenced by summer and winter monsoonso when the winds change direction, the

surface currents also change direction

More Ocean Circulation Patterns

Ocean Currents of the World

• 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 latitude

Cold currents- move from high to low latitudes( moderate temperatures in tropics and mid-latitudes)

Benguela Current (western Africa), Peru Current, California Current

Cause 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

Ocean currents

Peru Current

"GS103 - Lecture Outlines Sp08." GS103 - Lecture Outlines Sp08. Web. 22 May 2013. <http://nsm1.nsm.iup.edu/hovan/classes/GEOS103_OL_sp08.html>.

•Upwelling is the rising of cold water from layers below the surface.o Induced by windo Brings nutrient rich water to the surface

Supports marine organisms

•Most common on west coastso Most distinguished: California, Western South

America, and West Africa

•Cause of upwellingo Coastal winds and Coriolis effect cause

surface water to move away from the shore

Upwelling

Upwelling

•Cause of upwellingo Cold water from below replaces warmer

surface water Results in lower surface temperatures

• For example, Atlantic temperatures in August are 21°C or higher and Pacific temperatures are 15°C

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

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.

Thermohaline Circulation

Thermohaline Circulation. 2011. Photograph. N.p

Various Components of the Coastal ZoneShorelines Are Dynamic-• topography • geologic makeup• climate

Shore- area that extends between the lowest tide level and the highest elevation on land that is affected by storm waves

Shore is divided into two parts- Foreshore-area exposed when the tide is out and

submerged when the tides in Backshore-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 tide

Offshore Zone-seaward of the nearshore

Shoreline- line that marks the contact between land and sea

Various Components of the Coastal Zone

Coast-extends inland from the shore as far as ocean related features can be found

Coastline-marks the coast's seaward edge, whereas the inland boundary is not always obvious or easy to determine