Transcript ocean currents - Team Strength

OCEAN CURRENTS
OCEAN CIRCULATION
 Of the four systems on earth, the
hydrosphere is what separates us from
the other planets.
 Earth’s vast quantities of water make
life as we know it possible
 About 70% of Earth’s surface is covered
in water - most of which is found in the
oceans
SURFACE CURRENTS
 The ocean is not still, like a pond - it moves in
distinct patterns called currents.
 Some currents flow nearer to the surface
Surface Currents
 These currents are driven by several different
forces
 Solar radiation
 Wind patterns
 Coriolis effect
SOLAR RADIATION
 As energy from the
sun hits earth, it is
dispersed unevenly
across the latitudes
 This uneven heating
causes air to rise
and fall over the
surface of the earth
in distinct patterns
SOLAR RADIATION
 More direct energy
from the sun hits
the equator.
 This air warms up
and rises and is
deflected either
eastward or
westward due to the
Coriolis effect
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CORIOLIS EFFECT
 The Coriolis
Effect is an
apparent
deflection of an
object moving in
a rotational
motion
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SURFACE CURRENTS
 The way in which the air moves across the
surface of the earth, directly influences how
surface ocean currents move
 Ocean currents develop due to friction
between ocean water and the winds that
blow across the surface.
 Ocean currents move in a pattern consistent
with the pattern of winds that blow across
the surface of the earth.
Ocean Circulation
DEEP WATER CURRENTS
 Some currents flow from the bottom of
the ocean upwards
Deep water currents
 These currents are caused mainly by
density driven forces and gravity
DENSITY
 Density is mass per unit volume (D=M/V)
 In Seawater density depends on two factors
 Temperature of the water  Volume
 Salinity of the water  Mass
 Changes in density cause water to rise and fall
 Less dense  water rises
 More dense  water falls
 These changes are what drives deep water
current
SALINITY
 An increase in dissolved
substances increases
the density
 Salinity tends to be
highest at the poles and
near the equator.
 Near the poles, water is
trapped in glaciers increasing the amount of
salt in the water
 Near the equator,
evaporation is high increasing the amount of
salt in the water
TEMPERATURE
 A decrease in
temperature causes an
increase in density - the
molecules are moving
slower and packed
closer together
 Density is greatest in
polar regions - high
salinity and low
temperature
 Temperature is the most
important factor in
density
THERMOCLINE
 The layer of ocean
water between 330m 1000m , where there is
a rapid change of
temperature with depth.
 The thermocline is
essentially non-existent
in high latitudes (polar
regions)
DEEP OCEAN CURRENTS
 Density Currents
 Dense water sinks and slowly spreads out
across the bottom of the ocean
 Most deep ocean currents begin in high
latitudes (poles) where temperature is low
and salinity is high.
 As the water becomes dense, it sinks and
spreads out over the floor of the ocean
DEEP OCEAN CURRENTS
 Evaporation
 Deep water currents can also exist as a
result of evaporation
 Evaporation of surface waters increases
salinity and thus the density of the water.
 This is evident in the Mediterranean Sea.
 A dense water mass forms on the surface,
sinks and flows into the Atlantic
CONVEYER BELT
CLIMATE
 The conveyer belt
system of currents
moves around the
globe, influencing
global climate
 Heat Transfer
CLIMATE
 Currents transfer heat as
they move across the
ocean
 When currents from
low-latitude regions
move to higher regions,
they move warmer
water to cooler areas on
earth.
Gulf Stream
 The Gulf Stream is a
warm water current
that brings warm water
from the equator up to
the North Atlantic.
 This allows regions in
northwestern Europe,
like Great Britian, to
experience milder
winters - despite their
latitude
CLIMATE
 Warm water
currents tend to
create milder
climates in normally
cooler regions Great Britian
 Cool water currents
tend to create cooler
than normal climates California coast is an
example.
- Polar currents bring
cool waters which
create cooler climates,
including extensive fox
and cool ocean waters.