9.1 oceans. the blue planet 71% of earth’s surface is covered by oceans and seas. the science that...
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The Blue Planet71% 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 OceansWorld Ocean is divided
into 5 ocean basinsPacific, Atlantic,
Arctic, Indian, and Southern Oceans Question:
What oceans are almost entirely in the Southern Hemisphere?
Pacific Ocean is the largest and deepest.
Arctic is the smallest and most shallow.
Answer: Indian and Southern Oceans
Topography is the shape of the land or ocean floor.
Ocean floor topography is like land: Volcanoes, Mountains, Plateaus
Ocean Topography
Mapping the Ocean FloorBathymetry measurement of
ocean depths and charting topography of ocean floor.
First Study of World Ocean was HMS ChallengerSailed under British FlagDecember 1872 – May 1876First research ship
TechnologySONAR (Sound Navigation and Ranging)
Before sonar, ocean floor was believed to be flat and smooth
Uses sound waves bounced of the ocean floorFirst 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.
SATELLITESSatellites bounce
microwaves (radio waves) off the ocean surface
Technology
SUBMERSIBLESSmall 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)
SALINITYSalinity - total amount of
solid substance dissolved in water.Units are parts per
thousandAverage salinity of the
ocean is 35/1000 (3.5 %)
Sources of Sea Salt (NaCl – Common table salt):Chemical weathering of
rocks on landUnderground volcanic
eruptions (gasses)
Variation in SalinityLow salinity - fresh
water from glaciers, melting sea ice, large rivers
High salinity - evaporation removes fresh water; formation of sea iceQuestion:
Would you expect the salinity at a river delta to be higher or lower than in the middle of the ocean? Why?
Answer: lower because fresh water is mixing with the salt water.
More solar radiation = Warmer WaterAt equator At water’s surface
Less solar radiation = Colder WaterNear polesIn deep water
OCEAN TEMPERATURE VARIATIONSOcean surface water temperature varies with
the amount of solar radiation (heat)
Thermocline – A layer of water in which there is a rapid change in temperature with depth.low latitudeAt 300-1000 m temperature is just
above freezingCreates barrier between marine
lifeIsothermal - near freezing from
surface to floor high latitude
Thermocline and Isothermal
Left side hints: therm = heat, iso is even/ same, cline = gradient
OCEAN DENSITY VARIATIONS
Remember: Low density on the topHigh density on the
bottomAs 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.