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 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 Floor Bathymetry measurement of ocean depths and charting topography of ocean floor. First Study of World Ocean was 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.

SATELLITES Satellites bounce microwaves (radio waves) off the ocean surface Technology 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 Low salinity - fresh water from glaciers, melting sea ice, large rivers High salinity - evaporation removes fresh water; formation of sea ice Question: 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 Water At equator At water’s surface Less solar radiation = Colder Water Near poles In deep water OCEAN TEMPERATURE VARIATIONS Ocean 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 latitude At m temperature is just above freezing Creates barrier between marine life Isothermal - 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 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