Download Rivers in the Sea

Rivers in the Sea
Weather Dynamics
Science 10
Ocean Currents
• Surface winds start a process which creates
giant rivers in the seas, also known as ocean
currents.
• Warm water is pushed from the equator to
the poles
• Cool water is pushed from the poles to the
equator.
• Two other factors that affect/create ocean
currents are continents and the Coriolis
effect.
• Why would continents affect ocean currents?
Ocean Currents
• Ocean currents are blocked and diverted by
continents, causing them to bend and turn.
• The Coriolis Effect influences ocean currents
in the same way it influences the wind. Due
to the rotation of the Earth on its axis, the
oceans two are in constant motion.
• Ocean currents turn to the right in the
Northern Hemisphere and to the left in the
Southern Hemisphere.
Gyres
Gyres
• All 3 factors mentioned create the ocean
currents
• When we look at ocean currents on Earth a
pattern emerges.
• Ocean current tend to flow in circular
currents all around the Earth.
• These circular currents are called Gyres.
• They flow clockwise in the Northern
Hemisphere and counter-clockwise in the
Southern Hemisphere.
Eastern side of Gyres
• The right or east side of Gyres are cool.
• This cooler current caues the air above it to
be cool as well.
• This cooler air cannot hold as much water
vapour as warm air.
• Consequently, if this air moves ashore, there
is little condensation and very few clouds
form here.
• Some of these regions are even desert like
due to small amounts of precipitation.
Western Side of Gyres
• The left or west side of most gyres are warm.
• Thus, in these areas large amounts of water
vapour exist in the air.
• When this warm, humid (saturated) air
moves ashore, rain often follows.
• Hence rain forests and lush jungles forming
here.
• The warm currents warm the air.
• Therefore, some climates near these gyres
are warmer than they should be for their
latitude.
Great Ocean Conveyer Belt
• Ocean currents do not just move water
around from the equator to the poles.
• Ocean water below 100m in the ocean is not
affected by the Earth’s wind.
• Ocean water at these depths move vertically
up and down.
Great Ocean Conveyer Belt
• Cold water, like cold air, is more dense than
warm water, and therefore sinks.
• Cold water from the poles flows deep in the
ocean until it reaches a warmer zone closer
to the equator.
• Here the water warms and rises in the
ocean.
• This occurs more than once during the
extensive travels of water in the ocean,
warming and cooling depending on its
location.
Great Ocean Conveyer Belt
• The ocean conveyer belt is important for
transporting energy and nutrients from pole
to pole, around the Earth.
• Many species of fish, krill, and other shellfish
rely on the ocean conveyer belt to sustain
life.
Upwelling
• If a constant wind blows from shore, it blows
the water on the surface of the ocean out
from shore as well.
• These leaves a low density area for colder
water to rise up along the coast. This is
called an upwelling.
• Upwellings bring up rich nutrients that have
settled on the bottom of the ocean.
• Schools of fish are attracted to areas where
upwellings occur for this reason, and are
therefore excellent places for fishermen to
fish.
Trade Winds
• Upwellings occur off the west coasts of
continents within or near tropical climates.
• This is because trade winds which blow
toward the equator from east to west, blow
the water away from shore on the western
coasts of continents near the equator.
El Niño
• Trade winds blowing water westward,
causes it to pile up on shores like Australia
(to the east) and warm.
• For a reason still unknown today, at times
the trade winds will diminish and actually
blow in the opposite direction, pushing the
warm water from the east westward.
• The normally cooler water is suddenly
warmed very quickly and is called El Niño.
• At times the temperature changes can be
very severe.
El Niño
• Some of the most severe El Niño's from the
past have caused worldwide problems:
– The temperature decrease on the East causes
droughts due to loss of water vapour in the air.
– The temperature increase on the West causes
floods, monsoons, and severe storm systems due
to the increases water vapour in the air.
– The red tide, a huge algae bloom which flourish
due to increased temperatures in nutrient rich
water also form.
The Red Tide
• El Niño has been known to be a factor in promoting
algae blooms in the ocean.
• What are some of the problems that might be
associated with this?
• Algae, like other organisms in the ocean require
carbon dioxide and other gases and nutrients to
survive.
• With a huge spike in algae, they use up all the carbon
dioxide and nutrients in the water causing fish and
other life forms to be starved of food and other
resources.
• Water based plants to die off due to lack of carbon
dioxide to breath.
• Plants cannot get light to utilize photosynthesis
The Red Tide
Do You Understand?
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6.
Name three factors that determine the
speed and direction of surface currents in
oceans.
Describe two ways that ocean currents can
influence the climate of coastal regions.
Under what conditions will cool water rise?
Describe two events that occur while an El
Niño is developing.
What are some negative affects of El
Niño?
What is the red tide? Why is it bad?