Transcript Chapter 15
Chapter 15
Section - 1
Factors that Influence Ocean
Currents
• 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 surface
o some currents are short- lived and affect
only small areas
these are a response to local/seasonal
influences
o 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
•
Ocean Circulation Patterns
Gyre = the large circular surface current pattern found in each ocean
o eg, North Pacific Gyre
the center of each gyre coincides with the subtopics at about 30
degrees North or South latitude, so they are often called
subtropical gyres
there is a correspondence between the direction of surfacecurrent flow and the major wind belts of the world
subtropical gyres rotate clockwise in the Northern Hemisphere,
and counterclockwise in the Southern Hemisphere
this is because wind generates surface currents, as well
as...
o the Coriolis Effect
the deflective force of Earth's rotation on all freemoving objects, including the atmosphere and
oceans
there are four main currents within each gyre
if an object is dropped into a gyre it would take about six years to go
completely around
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More Ocean Circulation Patterns
• the circular motion of gyres leaves a large
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central area that has no well-defined
currents
o 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 monsoons
o when the winds change direction, the
surface currents also change direction
Ocean Currents of the World
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 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
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
• Upwelling is the rising of cold water from
layers below the surface.
o Induced by wind
o Brings nutrient rich water to the surface
Supports marine organisms
• Most common on west coasts
o Most distinguished: California, Western South
America, and West Africa
• Cause of upwelling
o Coastal winds and Coriolis effect cause
surface water to move away from the shore
Upwelling
• Cause of upwelling
o 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 Zone
Shorelines Are Dynamic-
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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 storms
Two 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