Oceanography Cont.

More about Ocean Water• Salinity – the amount of dissolved salts in

ocean water. 1 kg of ocean water contains 35 g of salt (average 3.5% of ocean water). Salinity is generally the same everywhere except in areas with low precipitation and warm climates where it is elevated.

• Nitrogen, carbon dioxide, and oxygen are most abundant at the ocean surface. Warm water holds less dissolved gas than cold water so near the poles oxygen rich water is colder and sinks allowing fish to live at greater depths.

Shoulder Partner

• We know there is salt in the ocean water, but what causes some areas to be more salty than others?

Salinity Variation• Salinity is higher at the equator because

water is evaporated at a higher rate.

• Salinity levels range from area to area and are effected by evaporation rates, runoff rates, and mixing of fresh/salt water (estuary).

Life in the oceans…

• The animals/plants in the ocean are classified into 3 major groups according to habits and depth.

First life group• Plankton –largest group. They

float at or near the surface where sunlight penetrates. They live at depths of up to one meter but can be as deep as 200m. Most are microscopic and drift with currents/tides. Baleen whales strain this life form from the ocean waters as their food source.

Plankton

Second life group

• Nekton –can swim and actively search for food and avoid predators. Found at all levels of the ocean.

Giant Squid

Third life group

• Benthos –live on the ocean floor. Some are plants in shallow waters while others are oysters, crabs, etc... Only few live in the deepest part of the ocean.

Face Partner

• Which life form would you classify a jellyfish?

• Be able to justify your choice.

Life in the Oceans…

Life Zones• Intertidal/littoral zone –

lies between the low and high tide. It is hard for things to survive here because of constant movement.

Life zones cont…• Neritic/Photic zone –from

low-tide line to the edge of a continental shelf. A depth of about 200 m and receives lots of sunlight. Water pressure is low and the temp. is fairly constant. Floor is covered with seaweed. Most rich in life; world’s greatest fishing zones.

Neritic Zone

Still one more life zone…• Open – ocean zone – broken into two smaller

zones.– Bathyal zone – from the continental slope

down about 2000 m. Sunlight does not penetrate .

– Abyssal zone – down 6000m and is the flat plains on the ocean floor. No sunlight and little food. Water pressure is very high. Temperatures are extremely cold. Most animals are small and strange looking. Some create their own light.

Bathyal and Abyssal Zones

Table Talk

• What kind of traits would deep ocean life have to have in order to survive?

• How do you suppose they look?

Life in the Deep Zone

Mapping the Ocean Floor• 1872 –Challenger used

wire to measure ocean depth, collected animals/water samples and used special thermometers to record temps. Mapping the ocean floor is done by echo sounding, radar, sonar. The most complete picture was gathered by Seasat, a satellite launched in 1978.

Mapping the Ocean Floor

Shoulder Partner

• Explain why the ocean floor has been mapped by sonar and satellite only.

• What is sonar anyways?

Tidal vocab and facts• Tides are caused by a giant bulge of

water.• One low-tide/high-tide cycle takes about

12 hours and 25 minutes.• Tides tend to be highest where the

gravitational force between the earth and the moon are strongest, along with the opposite side of the earth.

• Tidal range = the difference between high and low tide.

Moving Ocean Waters• Waves –energy that moves

through the ocean but does not carry matter. Created by wind. The height of the wave depends on wind speed, the length of time the wind blows, and the distance traveled. Increasing any of these, increases wave size.

• Interesting Fact: The highest wave ever noted was 135 ft high.

Wave facts…• As a wave travels in shallower water it slows and falls

forward as a breaker.

• Most waves are wind generated.

• When a wave passes through the ocean, individual water molecules move up and down, but not forward or backward.

• Friction causes the water to move along with the wind.

Parts of a Wave

• crest – highest point

• trough – the lowest point

• Wavelength from crest to crest or trough to trough.

• Wave-height from trough to crest.

Killer Waves• Tsunamis – ocean waves

caused by earthquakes. Japanese word meaning “large wave in a harbor”.

• They are very strong, fast moving waves.

• Wavelengths up to 300 miles and speed up to 600 mph.

• In the open ocean they may only have a height of 3 feet. But, reach 150 feet at break.

Table Talk

• Can someone surf a tsunami and live to tell about it?

• Why or why not?

Can You Surf a Tsunami?

Currents• Surface current –caused by

wind Ex. Gulf Stream carries warm water from Florida north along the U.S. east coast. Long distance surface currents are controlled by global winds and short distance by local wind patterns.

• Move 100km/day

• Gyre – huge rotating systems that dominate the surface of the oceans. Movement is directed by the Coriolis Effect.

More currents…

• Longshore current – pulls you parallel (sideways) to the shoreline.

• Rip tide current –a strong channel of water flowing seaward from near the shore. Also, fast-moving water that can pull a swimmer rapidly out to sea

Currents continued…• Deep currents (turbidity currents) – caused by

differences in density of water and flow opposite of surface currents. The densest ocean water is near Antarctica due to changes in salinity and temperature. They move slower than surface currents. Can take 1000 years to make a complete cycle around the ocean floor.

• As the deep Antarctic currents come close to land, the ocean floor rises, forcing the cold currents upward. This process is called upwelling. It carries rich foodstuff with it (dead animals and plants) which causes an area with plentiful ocean life.

• Coriolis effect causes currents to swirl to the right in the N. Hemisphere and to the left in the S. Hemisphere.

Currents to know…• Gulf Stream – warm, located off the coasts of

the United States and brings warm water up the coast towards New York.

• California Current – cold, located off the west coast of the United States and brings cold water from the poles down toward the equator.

• Humbolt Current – major upwelling cold current off the coast of Peru. Great fishing area.

The end Oceanography part II!