1	Oceanography How important is the ocean in the Earth system?
2	Oceanography The scientific study of the ocean using chemistry, biology, physics, geology, and other sciences Oceans cover more than 70% of Earth’s surface HMS Challenger- 1^st large-scale ocean research project (1872)
3	Tools Scientists Use to Study the Oceans sonar deep sea corers mini submarines satellites buoys
4	Properties of Ocean Water Salinity and Temperature are two characteristics of water masses that help scientists study oceans and their behavior. Salinity- a measure of the dissolved salts in water Oceanographers calculate salinity by measuring the electrical conductivity of seawater (the greater the quantity of dissolved salts, the stronger the electric current).
5	Composition of Seawater Chloride- 55% Sodium- 31% Sulfate- 8% Magnesium- 4% Others- 2% Ocean water contains salts in the form of dissolved ions The most common salt in seawater is Sodium Chloride (NaCl) Humans and marine life depend on the elements found in ocean water
6	Salinity Variations Salinity is higher in areas that are extremely hot or cold. In hot, dry climates, oceans lose water rapidly because of evaporation, leaving salts behind (greater salinity). This occurs between 20° and 40° north and south of the equator. In polar climates, when seawater freezes, only freshwater ice forms, leaving salts behind in the remaining water.
7	Temperature of the Oceans Ocean water is heated by the sun, but sunlight is only absorbed in the top few meters of water, leaving the rest of the ocean water very cold. Ocean temperature decreases rapidly with depth!
8	Ocean Temperature Zones Mixed Layer (ocean’s surface region) Middle Zone (thermocline) Deep Water (polar water)
9	Mixed Layer Layer at the ocean’s surface where wind and waves mix heat evenly Absorbs almost all of the sun’s light Most marine life is found in this layer
10	Middle Zone Also called the thermocline This layer is found directly beneath the mixed layer. Temperature drops very rapidly here.
11	Deep Water Zone This layer contains polar water masses that are very cold and dense. This cold, dense water moves away from the polar regions along the ocean floor and spreads itself over the globe beneath other ocean water. Here, temperatures are about 2°C.
12	Ocean Life
13	Photosynthesis in the Oceans Occurs in the mixed layer Many types of photosynthetic organisms live here Phytoplankton (single-celled organisms that float freely) are the most common Diatoms, a type of phytoplankton, are the primary energy source for the marine ecosystem
14	Marine Animal Life Marine animals need phytoplankton to survive These include Zooplankton, coral, and nekton (free-swimming organisms such as fish, reptiles, whales, squid, jellyfish, etc.)
15	Deep Ocean Life Deep in the ocean there is very little sunlight and oxygen, but some animals do survive. The animals live near vents, called smokers. Smokers are vents that release hot water into the cold deep ocean water. This allows bacteria to survive, which then becomes food for other organisms.
16	Black Smokers
17	Studying the Ocean Floor How do scientists study the ocean floor? Echo sounding (sonar)- A device sends a sound signal through the water to the sea floor. Scientists track how long it takes for the signal to reach the bottom and echo back to the surface. Sediment sampling- Core samples of the ocean floor are taken. The layers are studied to see how climate and atmosphere have changed over millions of years.
18	Studying the Ocean Floor How do scientists study the ocean floor? Satellite Observations- provide a greater range and speed in the mapping process. Signals bounce off the oceans surface, which gives information about what lies beneath the surface (ex. It is slightly higher over undersea mountains and slightly lower over trenches).
19	Parts of the Ocean The Continental Margin The continental margin is the underwater part of the continental crust. The margin consists of the continental shelf, the continental slope, and a continental rise or trench. Continental shelf- part of a continent that extends from the shoreline to the continental slope
20	Parts of the Ocean The Continental Margin Continental slope- begins at the shelf edge, where water depth begins to increase rapidly Continental rise- several kilometers thick, and descends gradually from the continental slope to the ocean floor Not all continental margins have continental rises. Some will have a trench instead.
21	Active Continental Margins Occurs when an oceanic plate subducts under a continental plate. Continental shelf is narrow Continental slope is steep Trenches are present here instead of a continental rise ex) The western coast of South America
22	Passive Continental Margins Not located at plate boundaries This margin is very broad and ends at the continental slope. Ex) The Atlantic Coast of North America
23	Submarine Canyons Large underwater valleys Can be created by turbidity currents (great landslides of mud and sand that speed down continental slopes) Turbidity currents carve a canyon from the continental shelf to the ocean floor
24	Ocean Basins Ocean basins have a wide range of topographical features. These features include abyssal plains, abyssal hills, island arcs, fracture zones, seamounts, guyots, and coral atolls.
25	Abyssal Plains and Hills Abyssal Plains the flattest of all Earth’s surfaces composed of sediments from continents that were deposited there Abyssal Hills small, rolling hills that often occur in groups next to oceanic ridge systems
26	Deep Sea Trenches Long, narrow, steep-sided troughs that run parallel to continental margins or to volcanic island chains (island arcs) Oceanic-continental convergent boundary- marginal trench forms a line of volcanoes on the overriding continental plate forms Oceanic-oceanic convergent boundary- volcanic island arc forms on the overriding oceanic plate
27	Deep Ocean Vents and Mid-Ocean Ridges Black smokers (geyser that erupts under water) are created along mid-ocean ridges Mid-ocean ridges form at divergent boundaries and create rift valleys and fracture zones
28	Seamounts and Guyots Seamounts Cone-shaped mountain peaks that rise high above the deep ocean floor Typically found in clusters or rows Ex) The Emperor Seamount Chain Guyots Flat-topped seamounts Tops were removed by wave action when they were above sea level Sinking of oceanic crust then lowers the tops of the guyots
29	Atolls An atoll is a ring-shaped coral island. These form when a coral reef develops around a volcanic island. When the oceanic crust beneath the island sinks, it will go beneath sea level, leaving behind a circle of coral reef (barrier reef) with a lagoon in the middle.
30	Ocean Floor Sediments Sediments cover the ocean floor in thick layers. Sediments include sand, muds, clays, and oozes (sediments made from microscopic shells from dead organisms)
31	Terrigenous Sediments Sediments that come from continental rocks and minerals broken down through weathering and erosion. Can leave the continents by river or as icebergs broken off of glaciers that melt in the ocean water
32	Biogenous Sediments Sediments on the ocean floor that come from living sources (oozes) These sediments are made mostly of shells and skeletons of marine animals
33	Hydrogenous Sediments Form when chemical reactions cause minerals to crystallize from seawater The most common type are manganese modules These lumps of minerals contain important metals that are important for industry
34	Why are ocean floor sediments important? Layers of sediment contain important information about Earth’s history, such as the pattern of changes in Earth’s climate. Scientists can also study the remains of sea creatures, the history of water temperatures on the ocean floor, and past behavior of prevailing winds.
35	The Moving Ocean What types of currents flow at the ocean’s surface? What drives ocean currents below the surface? What factors influence the rising and falling of the tides?
36	Ocean Currents Ocean currents involve large water masses and are any continuous flow of water along a broad path in the ocean. Currents can flow at the surface or far below it.
37	Global Ocean Currents
38	Surface Currents A surface current is an ocean current that generally flows in the upper 1000 meters of the ocean. This type of current is created by wind. Surface currents in the Northern Hemisphere turn clockwise, and in the Southern Hemisphere turn counterclockwise. (see p. 4 in your reference tables!).
39	Surface Currents Currents that flow away from the equator carry warm water, and currents that flow toward the equator carry cold water. Earth’s rotation and presence of continents influence the paths of currents, but surface currents are mainly caused by wind.
40	Winds Trade winds and westerly winds form most ocean currents. The trade winds blow from the NE in the Northern Hemisphere and the SE in the Southern Hemisphere The westerlies blow from SW in the Northern Hemisphere and the NW in the Southern Hemisphere
41	Types of Surface Currents Warm currents- flow away from the equator (ex. The Gulf Stream in the North Atlantic) Cold currents- flow toward the equator (ex. The California Current in the North Pacific) Gulf Stream Rings-eddies or whirlpools that break away from the edge of a current Countercurrents- flow in the opposite direction of the wind-related currents (occur along the equator)
42	Currents Below the Surface These currents are driven by gravity and differences in density. A density current is heavier and denser than surrounding water. These currents sink toward the bottom of the ocean where they circulate for 500-2000 years before resurfacing. These are found in all oceans.
43	Density Currents from Polar Water The most dense water comes from the poles. There are three main water masses: Antarctic Bottom Water, North Atlantic Deep Water, and Antarctic Intermediate Water Antarctic Bottom Water is the coldest, densest water (-0.4°C)
44	Density Currents Caused by Evaporation When seawater evaporates, salt in water is left behind, increasing both salinity and density of the remaining water. An example of this is in the Mediterranean Sea. Water here is very dense.
45	Upwelling Upwelling is a kind of vertical current in the oceans. It occurs when surface water is displaced by winds or density currents. The cold, deep water rises to replace the surface water.
46	Tides Tides are the periodic rise and fall of the ocean surface due to the gravitational pulls of the moon and sun. The position of the moons and sun relative to Earth affect the time and height of the tides.
47	The Moon and Tides When the moon is new or full, tides rise higher than normal. When the moon is at its quarter phases, tides are lower than normal. This is caused by gravity. Gravity is stronger when two objects are closer together!
48	The Moon and Tides The moon pulls the water on the side of Earth nearest it strongly. This creates a bulge in the ocean on this side and on the opposite side. Because the moon revolves around Earth, the bulges also move around the Earth. The moon rises about 50 minutes later each day, and so do the tides.
49	The Sun and the Tides The sun has the same type of effect on the oceans as the moon, but on a smaller scale because it is so far away. However, when the sun is in line with the moon and Earth, high tides are very high, and low tides are very low. This occurs twice a month and are called spring tides.
50	The Sun and the Tides At quarter phases, the moon and the sun are not in line with Earth, and the sun’s tidemaking effect is subtracted from the moon’s. When this occurs, high tides are not very high, and low tides are not very low. This also occurs twice a month and are called neap tides.
51	Spring Tides and Neap Tides
52	The Sun and the Tides Perigee When the moon is at perigee, it is at its closest point to Earth in its orbit. The tidal effect will be greater. Apogee When the moon is at apogee, it is at its farthest point from Earth. The tidal effect is less.
53	Tidal Range The difference in the water level between high tide and low tide is called the tidal range. Tidal ranges are more noticeable on oceans than lakes and vary greatly along the shores. The shape of the shoreline determines the tidal range.