Chapter 15

The Dynamic Ocean

Factors Influencing Surface Ocean Currents

• The ocean's surface currents follow the general pattern of the world's major wind belts

• Gyres: o slowly moving loops of watero centered in the subtropics of each ocean

basino the positions of the continents and the

Coriolis Effect affect water movement within gyres

Gyres:o Coriolis Effect:

An apparent force due to the Earth's rotation. Causes moving objects to be deflected to the right in the Northern Hemisphere and to the left in the Southern hemisphere. Coriolis force does not exist on the equator. This force is responsible for the direction of flow in meteorological phenomena like mid-latitude cyclones, hurricanes, and anticyclones.

Gyres:o Coriolis Effect:

causes subtropical gyres to move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere

o four main currents comprise each subtropical gyre

o five main subtropical gyres: Indian Ocean gyre North Atlantic gyre North Pacific gyre South Atlantic gyre South Pacific gyre

Deep-Ocean Circulation

• Deep-ocean circulationo Also referred to as thermohalineo It is caused by density variations

Density variations are caused by differences in temperature and salinity

o Most water involved in deep-ocean circulation begins in high latitudes at the surface Surface water becomes cold and salinity increases as sea ice forms

o When water becomes dense enough, it sinks forming currents

• Deep-ocean circulation Once it sinks, it stays the same temperature and salinity remain the

same while in the deep-oceano Antarctic water-surface conditions create the highest density water in the

world The water sinks to the seafloor It moves throughout ocean basins in sluggish currents

• Deep waters will not resurface for 500-2000 yearso Ocean-circulation is similar to a conveyer belt that travels from the Atlantic

through the Indian to the Pacific

Importance of Surface Ocean Currents

• Surface ocean currents have important effects on climate.o Currents moved from lower-latitude regions into higher

latitudes transfer heat from warmer to cooler areas on earth.o Warm ocean currents which are felt in the middle latitudes

in winter, the influence of cold currents is most pronounced in the tropics or during the summer months in the middle latitudes. As the cold currents travel equatorward, they tend to

moderate the warm temperature of adjacent land areas. Cold currents are also associated with greater fog

frequency and drought.

• Ocean currents also play a major role in maintaining Earth's heat balance.o they transfer heat from tropics, where there is excess

amounts of heat, to the polar regions.

• Ocean currents also play an important role in navigation.

Importance of Surface Ocean Currents

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Upwelling

•Upwelling o the rising of colder water from deep layers o wind-induced movement that brings cold,

nutrient water to the surface o It also affects the movement of animalso vertical water movementso a common type of upwelling is coastal

upwellingo brings greater concentrations of dissolved

nutrients, such as nitrates and phosphates, to the ocean surface

Upwelling

Coastal upwelling

•Coastal Upwellingo most characteristic along the west coasts of

continents (e.g; along California and western South America)

o occurs when wind blows toward the equatoro when combined with the Coriolis effect, water

moves from the shoreo slow upward movement of water from depths

of 50 to 300 meters ( 165 to 1000 feet) brings water that is cooler than the original surface water and results in lower surface water temperatures near the shore

Coastal upwelling

Various Components of the Coastal Zone

• Shoreo The area extending between the lowest tide level and the highest

elevation on land that is affected by storm waves.o The coast extends inland from the shore as far as ocean-related

features can be found. o The shore is divided into two parts.

Foreshore• Seaward of foreshore are the nearshore and offshore

zones. Backshore

• Landward of the high-tide shoreline• Usually dry, being affected by waves only during storms.

Nearshore• Lies between the low-tide shoreline and the line where

waves break at low tides. Offshore Zone

• Seaward of the offshore zone.

Various Components of the Coastal Zone

• Shore Beach

• An accumulation of sediment found along the landward margin of the ocean or a lake.

• May extend for tens/hundreds of km. along straight coasts.

• Formation may be confined to the quiet waters of bays.

Berms• Relatively flat platforms often composed of sand that

are adjacent to coastal dunes or cliffs and marked by a change in slope at the seaward edge.

Beachface• Wet sloping surface that extends from the berm to

the shoreline.

Works Cited "Coriolis Force." Definition. N.p., n.d. Web. 21 May 2013

"Ocean Gyre." Wikipedia. Wikimedia Foundation, 05 Sep. 2013. Web. 21 May 2013.