Physical Oceanography

Section 15.1 The Oceans

I will……….Identify methods scientists use to study Earth’s oceans.

Discuss the origin and composition of the oceans.

Describe oceans and major seas.

Oceanography- The scientific study of the Earth’s oceans.

The ancient Egyptians were the first to build seafaring ships, around 4000 b.c.

Oceans were used for travel, recreation and to obtain food.

71 % of Earth’s surface covered by oceans vast bodies of water affect:

Weather Climate Food supplies Recreation Global trade And marine life (such as humpback

whales)

In the late 1800’s, Challenger used measuring devices to investigate:

ocean currents water temperature chemical composition seafloor sediments topography

German ship Meteor 1920s– used sonar for first time Sound Navigation and Ranging

Uses the return time of an echo and the known velocity of sound in water to determine water depth.

Velocity of sound in water is 1500m/s Velocity of sound in air is 334m/s

Calculation:Ocean depth= sonar signal and time it returns or

echo

Distance to the ocean floor=time x 1500m/s divided by 2.

Satellites (Topex/Poseidon)– monitor ocean’s surface temperature

Submersibles (underwater vessels) – investigates deep trenches

Side-scan sonar (for mapping)- directs sound waves to the seafloor at an angle

Earth is about 4.6 billion years old. Scientists hypothesize that Earth’s water

could have originated from 2 sources:

1. Comets- (dust, rock particles mixed with frozen water and gases) Gases-water vapor, methane, ammonia

2. Volcanoes-(water vapor, carbon dioxide and other gasses)

97% Oceans (salt water) 3% Fresh water (frozen ice caps, rivers,

lakes, underground sources)

Sea Level- is the level of the ocean’s surface.◦ Affected by:

Melting of ice caps Tectonic forces

Trivia – avg. global sea level rising 1 -2mm/yr due to melting glaciers

71 % of the surface is covered with oceans. Avg. depth is 3800m All the oceans are interconnected, continents act

as huge islands. There are 5 oceans:

1. Pacific Ocean – contains ½ Earth’s seawater2. Atlantic Ocean – extends 20,000km3. Indian Ocean – located mainly in southern

hemisphere4. Antarctic Ocean – covered by sea ice5. Arctic Ocean – covered by sea ice

Smaller than oceans Mostly landlocked Exp:

Aral Sea Mediterranean Sea – first sea to be mapped by

Egyptians, Phoenicians, Greeks, & Romans Gulf of Mexico Caribbean Sea Bering Sea

We can usually see through the water in a glass, sink, bucket, or bathtub.

Thus, many people have the impression that water is transparent.

In reality, however, all water absorbs light.

In fact, a layer of ocean water 100m thick absorbs more than 99 percent of light.

This means that the oceans are essentially dark below a depth of 100m.

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