Transcript Earth: An Ever changing planet

9.1 Oceans
The Blue Planet
 71% of Earth’s
surface is covered
by oceans and seas.
 The science that
studies the world
ocean is called
oceanography.
Question: What’s the difference between an ocean
and a sea?
Answer: Seas are partially
surrounded by land.
Geography of the Oceans
 World Ocean is divided into
5 ocean basins
 Pacific, Atlantic, Arctic,
Indian, and Southern
Oceans
 Pacific Ocean is the largest and
deepest.
 Arctic is the smallest and most
shallow.
Question:
What oceans are almost
entirely in the Southern
Hemisphere?
Answer: Indian and
Southern Oceans
Ocean Topography
 Topography is the shape of the
land or ocean floor.
 Ocean floor topography is like
land: Volcanoes, Mountains,
Plateaus
Mapping the Ocean Floor
 Bathymetry measurement of  First Study of World Ocean was
ocean depths and charting
topography of ocean floor.
HMS Challenger
 Sailed under British Flag
 December 1872 – May 1876
 First research ship
Technology
 SONAR (Sound Navigation and Ranging)
 Before sonar, ocean floor was believed to be flat and smooth
 Uses sound waves bounced of the ocean floor
 First created in 1906 by Lewis Nixon to detect icebergs.
 Technology advanced to detect submarines during WWI.
Question:
What are other uses for SONAR?
Answer: Locate and monitor
ocean animals like whales.
Technology
 SATELLITES
 Satellites bounce
microwaves (radio
waves) off the ocean
surface
 SUBMERSIBLES
 Small underwater
crafts, both manned
and unmanned
March 25, 2012 James
Cameron reached a record 7
miles below the surface of the
ocean at the Marianna Trench
(deepest part of the ocean)
SALINITY
 Salinity - total amount of solid
substance dissolved in water.
 Units are parts per thousand
 Average salinity of the ocean
is 35/1000 (3.5 %)
 Sources of Sea Salt (NaCl –
Common table salt):
 Chemical weathering of
rocks on land
 Underground volcanic
eruptions (gasses)
Variation in Salinity


Question:
Would you expect the salinity
at a river delta to be higher or
lower than in the middle of
the ocean? Why?
Low salinity - fresh
water from glaciers,
melting sea ice, large
rivers
High salinity evaporation removes
fresh water; formation
of sea ice
Answer: lower because fresh
water is mixing with the salt
water.
OCEAN TEMPERATURE VARIATIONS
 Ocean surface water temperature varies with the amount
of solar radiation (heat)
 More solar radiation =
Warmer Water
 At equator
 At water’s surface
 Less solar radiation =
Colder Water
 Near poles
 In deep water
Thermocline and Isothermal
 Thermocline – A layer of water in which
there is a rapid change in temperature
with depth.
 low latitude
 At 300-1000 m temperature is just above
freezing
 Creates barrier between marine life
 Isothermal - near freezing from surface
to floor
 high latitude
Left side hints:
therm = heat,
iso is even/
same, cline =
gradient
OCEAN DENSITY VARIATIONS
 Remember:
Low density on the top
 High density on the bottom
 As salinity increases, density
increases
 As temperature decreases,
density increases

Question:
Where would you find the
most dense water?
Answer: High latitude!
Near freezing with high
salinity due to sea ice.
3 OCEAN LAYERS
 Surface zone – mixed density
& temperature

waves, sun’s energy,
constantly mixing
 Transition zone (Pycnocline)
–moves water from warm
surface layer above to cold
layer below
 Deep zone – No sunlight,
water temperature just above
freezing & density is high