Physical Oceanography UNIT 8 STANDARDS: NCES 2.1.1, 2.1.3, LESSON 1

Lesson Objectives In this lesson, you will learn about: –How scientists study oceans –How the oceans were formed –Where the oceans are located –How seawater and freshwater differ

Water Cycle over Seas The water of the sea returns in a cycle. Seawater evaporates and the water vapor forms clouds that are blown over land, Precipitation from these clouds soaks into the ground and flows back to rivers and streams carrying dissolved minerals with it.

Early Oceanography HMS ChallengerHMS Challenger A little over a hundred years ago, in 1872, a small sailing ship called the H.M.S. Challenger set sail from England. Enough material was collected to fill fifty volumes of information. The information collected by the Challenger was used mostly for shipping purposes. This voyage was the first systematic ocean study. The next big surge of scientific activity came during World War II. A knowledge of the sea was crucial then for military intelligence.

Modern Oceanography German research ship Meteor Today First ship to use SONAR Sound Navigation Ranging Side-scan Sonar Satellite Topex Poseidon Generated 3-D image of the ocean floor

Origins of the Oceans Where did the water come from?Where did the water come from? Volcanoes Comets that impact with the earth carry water trapped as ice. Meteors also contain water. Volcanoes are a main source of water vapor released into the atmosphere. Volcanoes release H 2 O, CO 2 Volcanoes continue to release water vapor today.

Distribution of the Earth’s Water Distribution Oceans contain 97% of the earth’s water. 3% is found in ice caps, rivers, lakes, and underground. Global sea levels have risen and fallen dependent on the amount of water trapped as ice. Plate tectonics also cause the sea floor to rise and fall and affects the sea level.

Major Oceans (1 Ocean System) 5 Oceans The Pacific Ocean –Covers the largest area—more than half of the water in the world The Indian Ocean –Third largest ocean in the world The Atlantic Ocean –Shallowest of the three largest oceans (3.93 km, feet) –Area of sea-floor spreading The Arctic Ocean –The smallest in area of the oceans –Has a very shallow sea floor The Southern Ocean (Antarctic) –Mostly covered with ice

The Blue Planet Oceanographic studies, as well as satellite photo of earth, have shown us that our planet Earth is a “planet of water.” Over 71% (about three- fourths of the earth’s surface) is covered by water. Water covers 61% of the Northern Hemisphere and 81% of the Southern Hemisphere.

Seas Seas are smaller than oceans Seas are partially or mostly landlocked. *All seas and oceans belong to the 1 world ocean. Their water is intermixed. Mediterranean Caribbean Sea Bering Sea Red Sea Black Sea

Section Review What is oceanography? What was learned from the Challenger expedition? What is sonar? Where did the water in the early oceans come from?

Seawater: (96.5% water 3.5% salts) Properties of seawater Salinity Composition Ocean water is different from water in lakes and streams. Ocean water tastes salty.  Saltiness- the major ingredient is sodium chloride.  More than half of the minerals found on land are also dissolved in ocean water. O 2 - ocean water also contains many dissolved gases. The most important gases are oxygen and carbon dioxide.

Salinity: amount of dissolved salts Variations Sources Freezing Point Salinity based on evaporation. Highest at equator, then tropics, subtropics and finally poles. (warm to cold water) Volcanic ash and the erosion of minerals from the land are sources. Seawater (salt water) has a lower freezing point than fresh water because of the dissolved salts. Salt water freezes near –2 o C.

Ocean Layering Temperatures Ocean temperatures are dependent on location and depth from the surface.Ocean temperatures are dependent on location and depth from the surface. Closer to equator = warmer Closer to surface = warmer Surface depth about 100 m Thermocline-transition layer Bottom layer-coldest water and also the deepest

Temperature Summary Two primary factors determine ocean water temperature: –The latitude of the body of water (the distance north or south of the equator). –The depth of the water. The winds of the earth drive warm ocean currents of the equator toward the North and South Poles. From the surface of the water down to about 91 meters (300 ft), the water temperature remains constant. From 91 meters to approximately 2,700 meters (3,000 ft), the temperature drops as the depth increases. Below 2,700 meters, the temperature is again constant. There is very little heat here. The temperature is very close to the freezing point of salt water (-2.2° C or 28° F)

Section Review What is the most abundant salt in seawater? How do salts enter the oceans? The salinity is higher in the tropics when compared to the polar regions, why? Explain why salt is used to de-ice roads