Earth ScienceCoach Williams

Room 310B

Physical Oceanography

Chapter 15

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

Section 15.1: The Oceans

The study of Earth’s oceans

Oceanography

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

Modern Oceanography

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

Origins of Oceans

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

Distribution of Earth’s Water

Oceans

Objectives:◦ Compare/contrast the physical and chemical

properties of seawater◦ Explain ocean layering◦ Describe the formation of deep-water masses

Section 15.2: 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

Chemical Properties of Seawater

Density: more dense than pure water >1◦ Salinity, temperature

Freezing point lowered (-2°C) Darkness: ocean water absorbs light (100m)

Physical Properties of Seawater

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

Ocean Layering

Warm tropic water rises Polar waters sink 3 Ocean Masses:

◦ Antarctic Bottom Water◦ North Atlantic Deep Water◦ Antarctic Intermediate Water

Water Masses

Water Masses

Objectives:◦ Describe the physical properties of waves◦ Explain how tides form◦ Compare/contrast various ocean currents

Section 15.3: Ocean Movements

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

forward

Waves

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

Wave Characteristics

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

Breaking Waves

Periodic rise/fall of sea level◦ High Tide: highest level◦ Low Tide: lowest level

Tidal range: difference between two levels

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

Causes of Tides

Density 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

Ocean Currents

Gyres

Movement of water up and down Brings nutrients from deep

Upwelling