2/23/2017
Oceans I Notes
Stella loves the Ocean, so
should you!
Outlines on the front table
Oceanography
the science of our
oceans that mixes
biology, geology,
chemistry, and physics
(among other sciences)
to unravel the
mysteries of our seas.
Divisions of Oceanography
• Chemical Oceanography –
study of chemical reactions
• Biological Oceanography –
study of living things in their
environment
Divisions of Oceanography
(cont.)
The Global Ocean
• Physical Oceanography –
• Covers 71% of the Earth’s
study of changes in motion of
sea water
• Geological Oceanography –
study of sediments &
topography
surface
• Salt Water
• 97% of all water on Earth
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The Hemispheres of the
Earth
Northern Hemisphere
39% land
“Land Hemisphere”
Southern Hemisphere
19% land
“Water Hemisphere”
Hydrosphere
• Describes the combined mass
of water found on, under, and
over the surface of the a
planet.
Composition of Seawater
Main salts/minerals present in oceans (ppt):
1. NaCl (halite) 3.5%
2. MgCl 2
3. Na2SO4
4. CaCl2
5. KCl and others…
Salinity – amount of dissolved salt in
water; usually expressed as parts
per thousand (ppt)
Where do the salts come
from?
1. Weathering of rocks and
minerals
2. Outgassing from Earth's
interior
3. Hard parts of marine
organisms (i.e., shell material)
Average salinity = 33 – 38 ppt (3.3-3.8%)
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What affects salinity?
What affects salinity?
• Increase salinity (remove water) –
– Evaporation
– Formation of sea ice
• Decrease salinity (add water) –
– Precipitation
– Sea ice melting
What is Ocean Water Composed of?
• Regions of heavy precipitation at the Equator
shows lower surface salinity than regions of
excess evaporation at the mid-latitudes that
shows increased surface salinity.
Divisions of the Global
Ocean
Pacific
• Pacific Ocean
• Atlantic Ocean
• Indian Ocean
• Southern Ocean
• Arctic Ocean
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Pacific Ocean
Atlantic
• Largest and Deepest
• Holds 50% of Earth’s ocean water
• Covers 31% of Earth’s surface
• Average depth = 4.3 kilometers
(2.7 miles)
• Mountain building along margins
• Abundant islands (mostly volcanic)
• Marianas Trench 6.8 miles deep
Atlantic
Ocean
Indian
• 2nd largest ocean
• 23% of Earth’s ocean water
• Avg. depth = 3.9 km (2.4
miles)
• Mid-Atlantic Ridge
• Few islands
• Large sediment deposits from
rivers (Amazon & Congo – 25% of
world’s river discharge)
Indian Ocean
• 3rd largest ocean
• Avg. depth = 3.9 km (2.4
miles)
• 20% of Earth’s ocean water
• Mostly in the S.Hemis.
• Abundant fresh water due to
river discharge (Ganges,
Brahmaputra, Indus)
Southern (Antarctic)
• “Defined” in 2000
• Starts at 60o S
latitude
• Surrounds
Antarctica
• 5.5% of ocean
water
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Arctic Ocean
Arctic
• 1.5% of ocean water
• Smallest & Shallowest
• Surrounds the North Pole
• Almost completely surrounded
by land
• Covered with sea ice most of
the year
• Extension of the Atlantic
Ocean Temperature
• Surface water temperature varies with
amount of solar radiation received
• Variation with depth –
– Low latitudes = rapid decrease in temp. w/depth
(thermocline)
– High latitudes = no rapid change in temp. w/depth
Ocean Density
Determined based on light:
Determined based on density:
• Density = mass/volume
• Depends on: temperature and
salinity
• Determines water’s vertical position
in the ocean
• Pure water = 1 g/cm3
• Remember – densest water is COLD
& SALTY
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Ocean Layers
Determined based on density:
Surface mixed zone
(Epipelagic): 2%, “sunlit
zone” warmest from solar
energy, mixed by waves, 300
m, most saline
2. Transition zone
(Mesopelagic): 18%,
“Twilight Zone”, 200 – 1000
m, includes thermocline
3. Deep zone (Bathypelagic):
80%, “Midnight Zone”, just
slightly above or below
freezing, not very saline
1.
Ocean Layers
• Determined based on Light
Photic Zone - Sunlit layer of water
• Deepest in tropics
• Typical value: 100 meters
• Photosynthesis occurs here
• Most ocean life found here
Aphotic Zone – Complete darkness
Circulation
• Atmospheric
Circulation
– Depends on density
• Surface Ocean
Circulation
– Depends on the wind
• Deep Ocean
The color red is the first color absorbed by water
so therefore most water we see is blue.
Circulation
Why is Ocean Circulation
Important?
Ocean Circulation
– Depends on density
• Transports heat
from equator to
poles
• Transport
nutrients and
organisms
• Influences
weather and
climate
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Upwelling is the force that
vertically moves cooler, nutrient
rich water from approximately
1000 feet below the surface to the
near surface.
Surface Currents
*Coriolis
Effect - ocean currents
are directed to the right
(clockwise) in the northern
hemisphere and to the left
(counterclockwise) in the
southern hemisphere
Deep Ocean Currents (Thermohaline)
Waves
Two factors are important in creating a dense mass of
moving water:
1. Temperature 2. Salinity
*Colder and salty water is denser than warmer, less salty water.
• A Wave is a rhythmic movement that carries
energy through matter or space.
• In oceans, waves move through seawater
Caused by:
• Wind
• Earthquakes
• Gravitational force of the Moon and Sun
(tides)
Parts of a Wave
Wavelength
Wave
Height
• Crest – highest point of a wave
• Trough – lowest point of a wave
• Wave Height – vertical distance
between the crest and the trough
• Wavelength – horizontal distance
between two crests or two troughs
Crest
Still Water
Trough
Wave Parts
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Waves Caused by Wind
Earth’s Oceans
• When wind blows across a body
of water, friction causes the water
to move along with the wind.
• Wave Height depends on –
–Wind speed
–Distance over which the wind blows
–Length of time the wind blows
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