Oceanography

1. Oceanography

2. The Oceans

3. Oceanography • Oceanography is the scientific study of Earth’s Oceans • Oceanographers study: • Chemical composition • Temperature • Movement of ocean water • Seafloor sediments • Topography • Marine Life

4. Earth’s Water • Ocean’s contain 97% of water found on Earth • 3% is located in frozen ice caps(Greenland, Antarctica) • Sea level has risen and fallen due to warming and cooling of the Earth • Tectonic Processes

5. Earth’s Oceans • Earth is known as the “Blue Planet” • 71% of the surface is covered by water • Average Depth is 3800 meters • Most landmasses are in the Northern Hemisphere • 81% of the Southern Hemisphere is water

6. Oceans and Seas • Oceans make up around 70% of the Earth’s surface • Divided into 4 Oceans: • Pacific-Largest • Atlantic-Between the Americas and Europe and Africa • Indian-3rd largest between Africa, Asia and Australia • Arctic-North of the Arctic Circle

8. Oceans and Seas • The Arctic and Antarctic areas are covered by sea ice • Ice is less dense than water therefore ice crystals form at the surface • Parts break up in the summer

9. Oceans and Seas • Seas are parts of the ocean that are partially landlocked • Black Sea • Mediterranean Sea • Caribbean Sea • Bering Sea • Seas that are completely landlocked have a different composition(More salt water) • Caspian Sea • Aral Sea

10. Studying The Ocean • The Challenger-Late 1800’s, British research ship • Investigated ocean currents, water temperature, sediments, topography • Used nets, dredges and other tools • Meteor- German ship in the 1920’s • Used sonar, first to map the Mid-Atlantic Ridge

11. Ocean Origin • The Earth is believed to be 4.6 Billion years old • The Ocean’s are thought to be about that old • Ancient lava flows suggest this

12. Formation of the oceans • One hypothesis suggests that water was released from Earth’s interior by volcanism(out gassing) • As the Earth cooled this water vapor condensed and filled the oceans

13. Formation of the Oceans • The second hypothesis says that the water came from comets • The impact of comets releases water

14. Chemical Properties of Seawater

15. Properties of Seawater Properties of Seawater • Seawater is a solution of salts dissolved in water • Salinity is the concentration of all salts in seawater • Measured in grams of salt per kilogram of water or ppt • The average salinity is about 35 ppt • Seawater is a solution of salts dissolved in water • Salinity is the concentration of all salts in seawater • Measured in grams of salt per kilogram of water or ppt • The average salinity is about 35 ppt

16. Properties of Seawater • Most of the salt is NaCl which splits about in solution • Other ions: Sulfate, Magnesium, Calcium, Potassium, Bicarbonate

17. Variations in Salinity • The highest salinity is found in subtropical regions(20-30 latitudes) • The rate of evaporation exceeds the rate of precipitation • Polar regions have lower salinities

18. Variations in Salinity • Higher salinities are found in enclosed seas near deserts such as the Mediterranean Sea, Red Sea • The Baltic Sea receives fresh water from rivers, lower salinity • Estuaries are partly enclosed bodies of water at the mouths of rivers. Very low salinities(2-10 ppt)

19. Addition of Salt • The salinity of the oceans has remained fairly consistent over time • Volcanoes release chlorine and sulfur dioxide which dissolve in water • Weathering of continental rocks generates other ions in seawater

20. Removal of Salt • When water evaporates ions stay behind and form minerals • When organisms die ions in their shells, bones and death accumulate on the ocean floor

21. Density • Pure water has a density of 1 g/ml • Seawater ranges from 1.02-1.03 g/ml • This is due to variations in salinity and temperature • Density increases with increasing salinity. • Density decreases with increasing temperature • The salinity can alter the freezing point (-2 C)

22. Light Absorption • Water absorbs light. Intensity decreases with depth • The absorption of different wavelengths varies as well • Marine animals may appear red near the surface but look black at a depth of 10 meters

23. Temperature • The surface of the ocean waters 15 degrees C(Is warmer near the equator) • In the Polar regions the water is cold from the surface to the seafloor • After about 100 m of ocean to about 1000 m the temperature drops from about 22 C to about 4 C

24. Temperature • The zone of rapidly decreasing of temperature with depth is called the thermocline • After the thermocline the temperature is uniform at roughly 4 degrees Celsius • Caused by differences in density

25. Water Masses • Cold, salty water comes from the Earth’s poles • Sea ice forms  Salt ions are left behind  Water underneath sea ice is dense Sinks • The cold, salty water then migrates towards the equator

26. Movement of Ocean Water

27. Movement of Ocean Water • Oceans are always in constant movement caused by: • Variations in temperature • Variations in Density • Winds blowing across the water’s surface • Gravitational pull of the Moon and the Sun

28. Density Currents • The low temperatures of water at Earth’s poles are responsible for the movement of seawater • Salts accumulate beneath the ice which increasing the density of the seawater • The dense seawater sinks and moves toward the equator. This is called a density current

29. Upwelling • Upwelling is the process where cold water from the bottom of the ocean moves toward the surface • Occurs near continents. • Winds push water away from the land which is replaced by deeper water which rises • Upwelling water is rich in nutrients which supports marine life

30. Surface Currents • Surface currents are formed by Earth’s global wind systems • In the tropics trade winds blow from east to west, water moves in the same direction • Mid latitudes-Prevailing westerlies move from west to east • Polar Regions-Winds move from east to west

31. Surface Currents • Gyres are large circular current systems that flow from north to south • The Coriolis effect influences this • 5 major gyres: • 2 in the Pacific Ocean • 2 in the Atlantic Ocean • 1 in the Indian Ocean

33. Surface Currents • When a current encounters a landmass the water is deflected away from the equator • As the warm current moves North it cools and turns eastward • Gulf Stream-Flows along the east coast of North America

34. Waves • A wave is a rhythmic movement that carries energy through space or matter • Waves carry small amounts of water

35. Waves • Crest-Highest point of a wave • Trough-Lowest point of a wave • Wave Height-Distance between the crest and trough • Wavelength-The distance between two crests or troughs • Factors influencing wave height: • Wind Speed • Wind Duration • Fetch

37. Waves • Waves lose energy when they reach shallow water due to friction • As they slow they become higher and steeper • Breakers are collapsing waves

38. Tides • Sea level-Average height of the ocean’s surface • Tides-Periodic rise and fall of ocean waters caused by the gravitational attraction of the Moon and Sun

39. Tides • One full tidal cycle takes about 24 Hours 50 Minutes. • This is due to the Moon rotating around the Earth • Spring Tides-When the Moon is full or new. High tides are higher than usual, low tides are lower than usual • Neap Tides-The Earth, Moon and Sun form a right angle. Lower tidal range

40. Shoreline Features

41. Shorelines • Shorelines are shaped by waves, tides and currents by erosion and deposition • Ocean floor is shaped by tectonic processes

42. Erosion • Wave Refraction is the bending of a wave when it reaches shallow water • This is caused by wave speed and water depth • A wave will reach a headland first and will bend towards the headland

43. Erosion • Most of the energy is concentrated on headlands, therefore they undergo erosion • This forms a wave cut platform at the base of a steep cliff

44. Deposition • Coastal landforms are formed by sediment from eroded land that are carried to the oceans by rivers • When waves and currents slow down these sediments settle out and build coastal landforms

45. Beaches Beaches • A beach is a sloping band of loose sediment at the edge of an ocean • The size of the sediments depends on the energy of the wave that deposited it • A beach is a sloping band of loose sediment at the edge of an ocean • The size of the sediments depends on the energy of the wave that deposited it

46. Longshore Current • Sediment is deposited in areas where the current slows • Sandbars often form and run parallel to most beaches • Result from waves breaking and dumping sediment

47. Longshore Current • A longshore current is when a water approaches the shore at an angle • Prevailing winds and wave patterns influence which direction it will flow • Longshore currents causes and is wash up and down the beach in a zigzag pattern

48. Longshore Current • Gaps in the sandbars allow water to return to the ocean. This forms a rip current • Barrier Islands form when sandbars form at low tide and winds pile up sand

49. Barrier Island • Spit-Forms when longshore currents slow due to increased water depth • Baymouth-A spit that has grown across the mouth of a bay

50. Spit, Baymouth Bar