Oceans

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Oceans
What do you know about the
oceans?
Arctic
Ocean
Bay of
Fundy
Baltic
Sea
Persian
Gulf
Atlantic
Ocean
Pacific
Ocean
Indian
Ocean
Antarctic
Ocean
Oceans cover 2/3 of the Earth’s surface.
Fig. 16.1, p.400
Topography more varied with larger
elevation changes than on the Earth’s
surface.
15CO, p.374
•
•
•
•
Mid-oceanic ridges
Trenches
Island arcs
Hot spots
Highest mountain
Mt. Everest 8848
meters
Average elevation
of continents
840 meters
Sea level
Average depth
of oceans
– 3800 meters
Floor of central
oceans about
– 5000 meters
Deepest ocean trench
Mariana trench –
11,000 meters
Millions of square kilometers
Percent of Area
Fig. 15.3, p.377
How is the bathymetry
determined?
Sonar: measuring the
time sound waves take
to return to ship
Known facts:
•travel time to bottom and back
•Speed of sound in sea water
The distance is determined by plugging
these values into a simple formula
Satellite altimetry
• Dips and bumps are due
•
•
to variations in
gravitational force
Sea surface copies the
ocean floor surface
Differences are measured
using the time radar
signals take to travel
through the atmosphere,
hit the ocean’s surface,
bounce back, and travel
back to the satellite
Geosat satellite
• Launched in 1985
• Orbits the Earth in
•
•
about 14 hours
The Earth rotates
Satellite map of the
Earth’s topography,
1.5 years
For every increase of 1000 meters
on the seafloor, there is 1 meter
increase in height of water.
Geosat image of the ocean floor
Continental margins: where land
meets the sea
Atlantic Ocean: plate boundary is in the center of the ocean
basin, away from the continental margin
Passive margin: without a
plate boundary
Active margin: contains a
plate boundary
Variations in temperature:
From north to south due to
the Sun’s radiation
Changes in the Sun’s angle
cause variations in the amount
of solar energy reaching Earth’s
surface.
Variations in Sun’s rays with
latitude
Layers of the Ocean: what
determines the ocean’s layers?
Temperature: warmer at
equator cooler near the poles
Surface temperature variations
Temperature variations within
ocean basins: sketch and describe
Ocean basins
Salinity of Seawater
• Water is bipolar
• The cation sodium
•
•
attaches to the
negative side
The anion chlorine
attaches to the
positive side
The figure illustrates
dissolved salt
The amount of solid material
dissolved in water
Source of salts?
Chemical weathering of
rocks (dissolved load)
Volcanic activity:
outgassing
Do you think salinity varies
within ocean basins or is the
same?
On the surface?
Within the basin?
WHAT FACTORS MAY
CHANGE THE SALINITY?
Precipitation
Fig. 16.4, p.402
Salinity
Precipitation and Evaporation
Red-precipitation
Blue-evaporation
Density: how heavy something
is relative to its size
• What factors change the density of sea
water?
Temperature: increase,
decreases density
Salinity: increase,
increases density
Density determines the vertical
position
Photic zone: where light
penetrates; upper 600 ft or 200 m
Plankton:
microscopic animals
and plants
Diatom-phytoplankton
• bottom of the food chain
•Use basic nutrients from sea
water to produce skeletons and
soft tissue
• phytoplankton produce greater
than 50%
Zooplankton
Dinoflagellate- 250 microm.
Copepod1mm
Coriolis effect: earth’s rotation
causes gyres
Gyres or circular patterns in the
oceans create currents
Fig. 16.13, p.407
The Gulf Stream
Benjamin Franklin
described in 1770
Much more complex
On the surface
Fig. 16.12, p.406
Air Temperature is influenced by
ocean currents.
Ocean currents influence
climate
Upwelling
Orange and
yellow are areas
of high
chlorophyll
concentrations
Phytoplankton?
Upwelling
• Wind driven
• Wind blows water
•
away from shore
Cold nutrient-rich
water is “pulled” to
the surface
Upwelling: bottom waters are
nutrient rich
• Nutrients are
•
•
produced by bacterial
decay of material
Phosphates, nitrates,
carbonates
Provide nutrients for
plankton (base of the
food chain)
Upwelling: where
Upwelling: significance
• Supplies basic
•
•
nutrients for singlecelled organisms
Diatoms (plants)
Offshore Ireland
Red: highest
concentration
• Gravitational force of the moon causes the
oceans to bulge
• Periodic rise and fall of large bodies of
water
• The Earth turns on its axis, taking the
moon about 25 hours to make one obit in
our sky
• Two tidal peaks and troughs
Fluctuations due to the interaction of the sun,
moon and Earth
Centrifugal force of the Earth helps cause tides
Tides
Nova Scotia’s Bay of Funday
Spring Tides
• Full or new moon
• Sun and moon are aligned
• Strongest
Neap Tides
• Occur during quarter moons
• The position of the sun and moon are at
right angles
• Gravitational pull cancels
• Small increase or decrease of water level
Why is the ocean blue?
• Intensity of water at
•
•
•
different depths
Absorptions is greater
for longer wave
lengths-red
Ocean is blue
Most of the light is
absorbed in the few
meters of water
Did life begin in the oceans?
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