Earth Science Coach Williams Room 310B

Chapter 15 Physical Oceanography

Section 15.1: The Oceans Objectives: Identify methods used by scientists to study Earth’s oceans Discuss the origin and composition of the oceans Describe the distribution of oceans and major seas

Oceanography The study of Earth’s oceans

Modern Oceanography Sonar: SOund NAvigation and Ranging” Mapping ocean floors Side-scan sonar: angles Satellites: monitor water temp/ waves

Origins of Oceans Earth: 4.6 billion years old Ocean sedimentary rock Igneous rock- lava chilled quickly = water Where did ocean water come from? Meteorites colliding release water 0.05% of meteorites are water Volcanism: water vapor

Distribution of Earth’s Water Oceans: 97% of Earth’s water Freshwater/glaciers: 3% Sea Level: level of the ocean Ice makes sea levels vary Sea floor rising/falling 71% of planet is covered by oceans Major Oceans: Pacific, Atlantic, Indian Other oceans: Arctic & Antarctic Seas: smaller than oceans and usually land- locked

Oceans

Section 15.2: Seawater Objectives: Compare/contrast the physical and chemical properties of seawater Explain ocean layering Describe the formation of deep-water masses

Chemical Properties of Seawater 96.5% water & 3.5% dissolved salt (NaCl) Salt is metal & group17 on periodic table Salinity: amount of dissolved salt Average: 35ppt (parts per thousand) Lower: polar regions, river/ocean, high precipitation Higher: low precipitation/high evaporation Salt: Volcanism, weathering/rivers Dissolved gasses: O, N, CO2 Salt balance: precipitate, ocean spray, animals

Physical Properties of Seawater Density: more dense than pure water >1 Salinity, temperature Freezing point lowered (-2°C) Darkness: ocean water absorbs light (100m)

Ocean Layering Range of surface temp.: -2°C through 30°C (Avg=15°C) Depth & temp.: deeper = colder Temp. Profile: plots temp. with depth 3 Layers (based on temp./density) Surface layer Thermocline: rapidly decreasing temp. Bottom layer

Ocean Layering

Water Masses Warm tropic water rises Polar waters sink 3 Ocean Masses: Antarctic Bottom Water North Atlantic Deep Water Antarctic Intermediate Water

Water Masses

Section 15.3: Ocean Movements Objectives: Describe the physical properties of waves Explain how tides form Compare/contrast various ocean currents

Waves Wave: movement that carries energy Caused by wind Water moves up and down; energy moves forward

Wave Characteristics Crest: tallest part Trough: lowest part Wavelength: distance between wave Wave base: how deep water is disturbed ½ of wavelength Speed of wave affected by wavelength Speed = wavelength x frequency Wave height: distance from crest to trough Wind speed Wind duration Fetch: how much open water

Wave Characteristics

Breaking Waves Breakers: collapsing waves Friction with bottom slows water down Faster waves catch slower moving water Faster water at top Shapes shoreline

Tides Periodic rise/fall of sea level High Tide: highest level Low Tide: lowest level Tidal range: difference between two levels

Causes of Tides Gravitational pull: Earth, Moon, Sun Gravity depends on mass and distance Sun: larger mass (Solar Tides) Moon: closer (Lunar Tides) Spring tides: Sun/Moon/Earth aligned Tides are higher/lower than normal

Causes of Tides

Ocean Currents Density currents: Surface currents: Caused by density differences (salinity/temp.) Slow moving Surface currents: Wind driven currents Top 100m Faster Predictable patterns Gyres: circular current systems

Ocean Currents

Gyres

Upwelling Movement of water up and down Brings nutrients from deep