Transcript Oceans Tides and Currents Powerpointm

Composition &
Characteristics of Oceans
Earth’s oceans are all connected,
however, scientists separate the
ocean into five main oceans:
• Pacific Ocean – largest and deepest of the oceans; larger
than all of Earth’s continental land mass put together
• Atlantic Ocean – half the size of the Pacific, covers about
20% of Earth’s surface
• Indian Ocean – the third largest ocean that is located
between India, Africa and the Indonesian Islands
• Southern Ocean – surrounds the Antarctic continent and
is covered by ice part of the year
• Arctic Ocean – smallest and shallowest ocean that is
located near the North Pole and is also covered by ice part
of the year
seawater – water from a sea or
ocean that has an average salinity of
35 ppt (parts per thousand), or one
kg of ocean water contains about 35
g of salt
salinity – measure of the mass of
dissolved solids in a mass of water
Oceans are divided into zones
based on physical characteristics
that include sunlight,
temperature, salinity and density
Surface zone – area of shallow seawater that
receives the most sunlight; organisms that
perform photosynthesis are located here
Middle zone – receives very little sunlight and of
it only the blue-green wavelengths
Deep zone – plants that photosynthesize are not
found here because there is NO light; many
organisms produce light using chemicals in a
process called bioluminescence
Temperature – temperature changes from
surface to about 1000 m depending if located in
polar or tropical regions
Salinity – top 500 m of water is saltier in warmer
water than polar water since it evaporates faster
leaving behind salt at surface
Density – ocean water is layered since cold water
is denser than warm water and salt water is
denser than fresh water
Ocean Waves & Tides
Wave
Movement of energy through a body of water
usually formed when winds blow across the
water’s surface transferring energy
Parts of a Wave
• crest – highest point of wave
• trough – lowest point of wave
• wavelength – distance from one crest to another,
or from one trough to another
• amplitude – the amount of energy a wave carries
(measured from resting point to crest)
• frequency – number of waves that pass a point in
a certain amount of time
Tides
Daily rise and fall of Earth’s waters on its
coastlines caused by the gravitational
interaction of Earth, the Moon and the Sun
The gravitational force between the Earth and
the Moon produces two bulges on ocean
surfaces – one bulge on side of Earth facing the
Moon and the other on the side that’s facing
away from the Moon – these bulges represent
high tides.
Tidal Range
The difference in water level between a high tide
and a low tide and vary depending on the positions
of the Sun and Moon with respect to Earth
Spring Tide
The largest tidal range and occurs when Earth,
the Moon and the Sun form a straight line
Neap Tide
The lowest tidal range and occurs when Earth,
the Moon and the Sun form a right angle
Ocean Currents &
Climate
Currents
Large streams of
moving water that flow
through the oceans
• surface current –
wind-driven currents
which affect water to a
depth of several
hundred meters and
can move as fast as
100 km/day
How do winds impact surface
currents?
• Cause surface currents to flow in the direction
that the wind is blowing.
• Example: Jet Stream
Gyres
Earth’s oceans
contain large, looped
systems of surface
currents called gyres.
Gyres in the northern hemisphere circle clockwise.
Gyres in the southern hemisphere circle
counterclockwise this is known as the Coriolis
effect.
Coriolis Effect
Movement of wind and water to the right or left
that is caused by Earth’s rotation
Deep currents
Caused by differences in density of
ocean water
Deep currents - move and mix
water around the Earth, moving
slower than surface currents,
carrying cold water from poles to
equator
Upwellings – movement of cold
water to the surface to replace
warmer water and bring tiny
organisms, minerals and other
nutrients from deep ocean layers
keeping the ocean ecosystem in
balance.
What causes deep
ocean currents?
• The vertical movement of ocean currents
that mixes with deep waters. Caused by:
• Change in density: Denser water SINKS
– Change in temperature: Decreasing
temperature increases density
– Change in salinity: Increasing salinity
increases density
Climate
Pattern of temperature and precipitation typical of
an area over a long period of time
• Solar energy drives convection currents in the
ocean. Surface currents warm or cool the air
above it, influencing the climate of the land near
the coast.
Great Ocean Conveyor Belt
Another large system of ocean currents that
affect weather and climate. It is a global “belt” of
surface and density currents that distribute
thermal energy around Earth.
Cold water currents:
Bring cold water the
surface to warmer regions
(upwelling)
Warm water currents:
Bring warm water to
colder regions
How do currents affect climate?
• Water holds heat very well (high heat of vaporization!),
so ocean currents easily transfer heat across the Earth
• When currents from the equator (low latitude) move
towards the poles (high latitude), heat is transferred
from warmer to cooler areas
• As cold water currents travel toward the equator, they
help regulate the warm temperatures of nearby land
areas.
How do currents affect
coastal climates?
• Ocean currents are important to coastal regions
because they can warm or cool air
temperatures along the coast. Think about how
it tends to be warm/cold during the
winter/summer on the coast
• Interesting side note – the Atacama desert!
One of the driest places on earth is partially
caused by a coastal current
Atacama Desert
The Atacama Desert is one of the driest places on
Earth. The Atacama is in the country of Chile in South
America. In an average year, much of this desert gets
less than 1 millimeter (0.04 inch) of rain! That makes it
50 times drier than Death Valley in California.
The Atacama is the driest hot desert in the world.
There are some weather stations in the Atacama
where there has never been any rain! Not all deserts
are hot. The Dry Valleys in Antarctica are cold
deserts. They are the driest deserts on Earth.
The Atacama is also one of the oldest deserts in the
world. Scientists think parts of it have been dry for at
least 20 million years and maybe as long as 40 million
years. That is much older than other very dry deserts.
The Dry Valleys of Antarctica are about 10-11 million
years old. The Namib Desert in Africa is only 5 million
years old. Some dry river beds in the Atacama haven't
had water flowing in them for 120,000 years!
Why so dry?
Winds and Currents!
• First there are two air currents that bring dry air into the region,
second it is located in a “rain shadow” between two mountain
ranges (the Andes and the Chilean Coastal Range) and lastly the
cold ocean current call the Humboldt current carries water up
from Antarctica. The cold current of water cools the air as it is
coming in from the ocean stripping it of moisture because cooler
air can not keep as much moisture as warm air.
How do
ocean
currents
affect
climate?
• Ocean circulation can
result in climate
changes.
• El Niño: periodic
warming of the ocean
that occurs in the
central and eastern
Pacific
• Tends to happen AprilOctober
What
causes El
Nino?
• Trade winds normally
blow west towards the
Pacific and push warm
surface water away from
the coast of South
America and towards
Australia/Asia
• This water is cold and rich
in nutrients.
• During El Nino, trade
winds calm down in the
central and western
Pacific, causing warm
water to gather near the
surface.
http://usatoday30.usatoday.com/weather/
resources/graphics/2008-09-25-el-ninola-nina-affect-us-weather_n.htm
Normal conditions
During El Niño
What are the
effects of El
Nino?
• Mudslides in California
from heavy rain
• Droughts US Midwest,
Central America,
Australia
• Unusually mild winters
in eastern US
• Dying off of fish in
western Pacific because
of nutrient loss.
• ice storms in eastern
Canada and New
England