Physical Oceanography UNIT 8 STANDARDS: NCES 2.2.2, 2.4.1, 2.5.5 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 What causes tides, waves, and currents

Early Oceanography HMS 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? 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 H2O, CO2 Volcanoes continue to release water vapor today.

Distribution of the Earth’s Water 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) 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, 12880 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 Mediterranean Caribbean Sea Bering Sea Red Sea Black Sea 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 8.1.1 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. O2- 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 –2oC.

Ocean Layering Temperatures 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 8.1.2 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

Ocean Movements: Waves Characteristics A rhythmic movement that carries energy through space or matter. Crest: the highest point on a wave Trough: the lowest point on a wave Wavelength: distance between 2 equal points on a wave Amplitude: wave height above or below the wave median Frequency: number of waves that pass a point in a given time.

Wave Height Depends on 3 factors Wind Speed Wind direction Fetch: amount of water available As waves reach shallow water, they slow down because of the friction with the bottom. The water behind the leading wave causes the wave height to raise. When the wave collapses, it is called a breaker.

Tides Tides High Tide Low Tide The periodic rise and fall of sea level The highest level the water reaches on the land The lowest level the water reaches on the land

Tide Table Lab Go to the Tide table lab in this unit. Graph the water level over time for the 24 hour period. Use curving lines to connect the points Estimate the approximate time of high and low tides from the graph

Causes of Tides Earth-Moon Sun The basic cause of tides are the gravitational attraction between the Earth, moon, and Sun. Unbalanced forces cause bulges on the side of the Earth closest to the moon or sun. Lunar Tides The Sun-Earth gravities also influence tides. Solar Tides Even though the moon is smaller, lunar tides are twice as high as solar tides due to the closeness of the moon.

Spring Tide vs Neap Tides Spring Tides happen when the moon and sun line up to pull on the water. These are the highest and lowest tides. They happen about every 14 days. New moon = highest Full moon = lowest Neap Tides happen when the sun and moon are at 90 degrees of each other. The sun pulls to the right on the water, while the moon pulls on the top or bottom to counter the solar tide.

Ocean Currents Density Current Surface Currents Caused by more dense water settling to the bottom and less dense water rising. Surface currents based on the direction of the prevailing winds. In the northern latitudes, trade winds move the currents from east to west. In the mid latitudes, westerlies move the current from west to east. In the polar areas, polar winds push the water from east to west.

Gyres: Large system of rotating currents If there were no land masses, the oceans would rotate east to west. But continents deflect the currents around.

Look at the overall currents

Upwelling Definition Origin Benefits Vertical movement of water. Upward currents of ocean water. Originate at the bottom of the sea and are COLD. Generally on the west coasts of continents. Abundant in nutrients and therefore support LOTS of marine life.

Section Review 8.1.3 Describe how water moves as a wave. What 3 factors determine wave height? What causes tides? Compare and contrast Neap and Spring tides. Why are the upwelling waters always cold? Predict the greatest fishing spots in the world and WHY.