Physical Oceanography Chap. 15 The Oceans Sea Water Ocean Movements

The Oceans – 15.1 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

Introduction Uses Studying H.M.S. Challenger travel fishing/food recreation Studying H.M.S. Challenger Meteor TOPEX-Poseidon Used sonar to map undersea topography NASA satellite that measures ocean data

TOPEX/Poseidon tracks ocean tides measures sea levels (to 5 cm accuracy) monitors climates by measuring ocean temperatures.

Ocean origins Oceans are as old as Earth’s rocks Lava flows have been dated at 4.6 b.y. These formed rocks by cooling quickly (in water)

Ocean origins Oceans are as old as Earth’s rocks Source of water Comets (dirty snow balls) Water was trapped in Earth when it formed. Volcanoes released this into the atmosphere.

The Hydrosphere Type Percentage Volume Used in Model Total 100 % 2000 mL Salt Water (oceans) 97.2% 1941 mL Fresh Water 2.8% 56 mL Ice 2.3% 46 mL Underground 0.4% 8 mL Surface ~ 0.05% 1 mL Soil & Air ~ 0.01% 0.2 mL

Earth’s Water Location Amount of frozen water has varied During ice ages as much as 10% of hydrosphere was frozen. Sea level varied by hundreds of meters. Due to melting of glaciers and tectonic forces altering sea floor.

Earth’s Water Most of Earth’s surface is covered by water (71%) The hemisphere contains higher percentage of water.

Earth’s Water Most of Earth’s surface is covered by water (71%) The southern hemisphere contains higher percentage of water. All oceans are connected. Pacific, Atlantic, and Indian oceans are main oceans. Seas are partly or mostly surrounded by land. Sea ice forms in the Arctic and Antarctic seas.

Seawater - 15.2 Objectives compare & contrast physical and chemical properties of seawater explain ocean layering describe the formation of deep-water masses

Chemical Properties Salinity Sea water is about 35 parts per thousand (ppt) salts Salts include Na+, Cl- , SO42-, Mg2+, Ca2+, K+, HCO3-, and others

Chemical Properties Salinity The salinity varies and is lower where there is . . . a lot of precipitation an estuary/river delta melting of glaciers

Chemical Properties Salinity Source of sea salt the atmosphere (Cl- and SO42-) weathering rocks (Na+, K+, Ca2+ from feldspar) 5. Removing sea salt deposited when water evaporates

Chemical Properties Salinity Source of sea salt Removing sea salt deposited when water evaporates carried via sea spray marine organisms use it in building shells, bones, and teeth

Physical Properties Density is greater than 1.00 g/cm3 Density of fresh water is 1.00 g/cm3 Freezing point is less than 0ºC Light absorption

Physical Properties Light absorption Water absorbs light Some colors penetrate further than others

Physical Properties Layers The deeper you go the cooler the temp. Temperature profiles show water depth/temperature relationship The thermocline is a layer in which the temperature decreases linearly with depth There is no thermocline for polar seas

Physical Properties Water masses Cold water comes from polar seas

Physical Properties Water masses Cold water comes from polar seas Surface water sinks as salinity increases due to sea ice formation

Physical Properties Water masses Cold water comes from polar seas Surface water sinks as salinity increases due to sea ice formation Deep currents carry water to the equator

Ocean Movements – 15.3 Objectives describe the physical properties of waves explain how tides form compare and contrast various ocean currents http://tv-antenna.com/heavy-seas/3/

Waves Periodic movement that carries energy from one place to another.

Waves Wave characteristics Crest Trough Wavelength Wave Height The peak of a wave Lowest part of a wave Distance between successive wave crests (or troughs) Depends on wind speed, wind duration, and fetch.

Waves Wave characteristics Breakers Waves slow down Waves become unstable Collapsing waves More friction with ocean bottom causes waves to slow. The tops of the waves collapse forward because the bottoms are being slowed

Waves Tides Periodic rise and fall of sea level.

Waves Tides High tide Low tide Highest level to which water rises (a bulge of water) High tide Low tide Lowest level water rises (caused by lack of water)

Waves Tides Types of daily cycles Semidiurnal Mixed Diurnal

Waves Tides Cause of tides Gravity from the moon pulls on earth/oceans Centrifugal motion moves the water away from Earth

Waves Tides Cause of tides During spring tide (unrelated to the season) high tides are highest During neap tide high tides are lower and low tides are higher than normal The sun influences tides to a smaller degree This is because of the greater distance between Earth and the sun (compared to Earth and the moon)

Ocean Currents Density currents Surface currents Move bottom water according to temperature and salinity differences Driven by surface wind. Follow global wind patterns Currents from the poles bring colder water, while currents from equator bring warmer water Gyres develop due to landmasses interacting with current flow Circular surface ocean currents

Major Ocean Currents

Ocean Currents Upwelling brings nutrient-rich water. Movement of cold water upward as surface water is blown by offshore winds

The End