Unit 5: Physical Oceanography The Motion of the Ocean…

1. Unit 5: Physical OceanographyThe Motion of the Ocean… Marine Science

2. Day 1: Atmospheric Circulation Objectives: • What is physical oceanography? • What are the layers of the atmosphere? • Explain how the surface of the Earth is heated. • What are convection cells? • What is the Coriolis Effect? • Explain the affect of the Coriolis Effect on global wind patterns. • Explain how land masses affect global wind patterns • Explain the difference between anabatic and katabatic winds.

3. Physical Oceanography • The study of physics within the marine environment. • This includes: • Sound • Waves • Currents • Tides • Light • How the oceans influence weather and climate

4. Atmosphere • The atmosphere is a mixture of gasses that extends about 90 km from the Earth’s surface • Differences in the heating of the atmosphere at different latitudes sets the gasses in motion… creating wind • Layers of the atmosphere: • Trophosphere • Stratosphere • Mesosphere • Thermosphere • The atmosphere is composed of: • Nitrogen 78% • Oxygen 21 % • Inert Gasses (argon, helium, neon) 1% • Carbon Dioxide (0.03) kidsgeo.com

5. http://forces.si.edu/atmosphere/04_00_01.html

6. Troposphere • Lowest Layer • Extends from the surface of the earth to an altitude of about 12 km • Temperature decreases with altitude at a rate of approximately -10oC for each 1000m of elevation • Where weather happens

7. Stratosphere • Where the ozone layer floats • Ozone Layer: Layer of O3 in the stratosphere that shields life from harmful ultraviolet radiation from the sun • Commercial airliners fly in this layer • From 12 to 50 km above Earth’s surface • Temperature increases with altitude because the ozone layer (O3) absorbs UV radiation from the sun (heat) theozonehole.com

8. Mesosphere • From 50-80 km above Earth’s surface • Temperature decreases as altitude increases • Space debris begins to burn as it enters the mesosphere… shooting stars blaze

9. Thermosphere • From 82-640 km above the Earth’s surface • Temperature rises • Northern and Southern lights occur here greenlandkid.com

10. Heating of the Earth’s Surface • Solar radiation from the sun heats the Earth’s surface • When the radiation hits Earth it is reflected, absorbed, or reradiated.

11. Heating of the Earth’s Surface virtualskies.arc.nasa.gov • The intensity of solar radiation varies with latitude

13. Heat Budget • More intense sunlight reaches the equator and the intensity of solar radiation decreases towards to the poles… • At high latitudes the same amount of sunlight passes through the atmosphere but the same amount of sunlight is spread over a larger area • To maintain a stable long term temperature, the Earth must loose as much heat as it gains • Excessive heat from the tropics tends to move to higher latitudes by winds and ocean currents

14. Heat Budget

15. Formation of Convection CellsNon-Rotating Earth • Equator receives more heat and has more warm moist air (less dense) • As this moist air rises this creates an area of low pressure • When moist air rises it condenses forming precipitation • The now dry air flows north or south (depending on the hemisphere) and sinks back down at the poles …. Then back to the equator… creating a large convection cells

16. Formation of Convection CellsRotating Earth • The Earth rotates and moves in an easterly direction at a speed of 1674km/hr at the equator • The rotation of the Earth affects the movements of the atmosphere, the ocean, and any other object not directly attached to Earth • Coriolis Effect: Deflection of objects in movement not directly attached to Earth theozonehole.com

17. mind42.com

18. Surface Wind Bands oneonta.edu

19. Effects of Continents and Seasons • Large land masses modify the atmosphere • Land masses have a lower heat capacity than water so they absorb and lose heat faster – changes temperature faster • 70% of land masses are in the northern hemisphere • During the summer, land is warmer than the ocean, causing a low pressure area over land (hot air rises) so there is a continuous low pressure area between 0-60 degrees north • During the winter, land is cooler than the oceans, causing a high pressure area over land (cold air sinks)

20. Local Effects • Land warms faster during the day and as this warm air rises it is replaced by air from over the ocean creating an on-shore breeze / sea breeze (anabatic wind) • At night, the air over land cools faster (sinks) than the ocean, and air flows out toward the ocean creating an off-shore breeze (katabatic wind) • This typically creates rain on the windward side of islands… nc-climate.ncsu.edu

21. Atmosphere Video Clip

22. Day 2: Hurricanes Objectives: • What are hurricanes? • Explain hurricane formation? • How are hurricanes measured? • Where do hurricanes get their name?

23. environment.nationalgeographic.com Hurricanes • Hurricanes are low pressure systems with winds greater than 74mph • Named for the location in which they are occurring: • Hurricanes are defined as storms over the North Atlantic or the Caribbean • In the western Pacific Ocean, hurricanes are known as typhoons. • Cyclones are hurricanes over the Indian Ocean. • Hurricane Formation • Form over warm tropical waters ( sea surface temps greater than 27oC) • Low pressure cells that occur in latitudes higher than 5o are set into a circular motion by the Coriolis Effect – this causes a circular pattern (counterclockwise in the northern hemisphere) • As the storm grows, the winds evaporate more water (and heat) which fuels the storm and creates a column of fast moving air • Hurricanes dissipate/stop when they travel over land because they lose energy

24. spaceplace.nasa.gov windows2universe.org

25. Hurricane Development • Tropical Disturbance: Group of thunderstorms with very little wind circulation • Tropical Depression: Storm with wind speeds up to 20 to 34 miles per hour • Tropical Storm: Storm with wind speeds reach 35-64 miles per hour. • Hurricane: When wind speeds reach 74 miles per hour or greater Hurricane Formation= http://news.bbc.co.uk/2/hi/science/nature/4588149.stm

26. Hurricane Development bom.gov.au

27. Measuring Hurricanes • Saffir-Simpson Scale. Scale that measures wind speed and air pressure of a hurricane. • Category 1- winds 74-95 mph, 64-82 kt, 119-153 km/h Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Branches of trees will snap, shallowly rooted trees may be uprooted. Power outages could last a few to several days. • Category 2 - winds 96-110 mph, 83-95 kt, 154-177 km/h Extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Shallowly rooted trees will be uprooted and block numerous roads. Near-total power loss is expected - outages that could last from several days to weeks. • Category 3 (major)- winds 111-129 mph, 96-112 kt, 178-208 km/h Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes. • Category 4 (major) – winds 130-156 mph, 113-136 kt, 209-251 km/h Catastrophic damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months. • Category 5 (major) - winds 157 mph or higher, 137 kt or higher, 252 km/h or higher Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.

28. Hurricane Facts • Hurricanes may have a diameter of 400 to 500 miles (640-800 kilometers). • The “eye” (center) of a hurricane can be up to 20 miles (32 km) across. The weather in the “eye” is surprisingly calm with low winds and clear skies. • Hurricanes hit land with tremendous force, bringing huge waves and heavy rain. • Many hurricanes cause severe flooding. • About 90 percent of the deaths that occur during hurricanes result from drowning in floods. • The world’s worst hurricane (for loss of life) took place in 1970 in Bangladesh. That hurricane created a flood that killed more than one million people. • Thunderstorms often form within hurricanes and produce tornadoes.

29. Damage from Hurricanes boston.com sitemaker.umich.edu uta.edu soest.hawaii.edu

30. Hurricanes in Media Literacy • Movie • Raging Planet – Hurricane • Hurricane Katrina - National Geographic geology.com

31. Tracking Hurricanes Hugo and Katrina… • Hurricane Tracking Video Clip • Hurricane Lab

32. Day 3: Oceanic Circulation Objectives: • What are the two main types of ocean circulations? • Explain the difference between upwelling and downwelling. • What are eddies? • What is a wave? • Label the parts of a wave. • Explain the difference between deep and shallow water waves. • What is a tsunami?

33. Ocean Currents • Ocean Currents: Continuous, directed movement of ocean water generated by forces such as breaking waves, wind, Coriolis Effect, tides, temperature, density and salinity differences • Major ocean currents are predictable – they have been described as rivers without banks • Types of Currents: • Surface – 0-400 meters deep – 10% of ocean currents • Deep – below 400 meters – 90% of ocean currents • Three major factors set ocean currents in motion: • Thermohaline Circulation (density driven) • Wind Driven Circulation • Changes in Sea Level

35. Thermohaline/Density Driven Circulation • Affect deep ocean currents • Density differences are occur as a result of temperature and salinity. • Warm water holds less salt than cold water so it is less dense and rises toward the surface while cold, salt laden water sinks. • As the warm water rises though, the cold water is forced to rise through upwelling and fills the void left by the warm water. • When cold water rises, it too leaves a void and the rising warm water is then forced, through downwelling, to descend and fill this empty space, creating thermohaline circulation. • Coldest water is at the poles and have higher salinities because of low precipitation and the formation of sea ice • Minute changes in density cause large changes in circulation… for this reason, oceanographers measure density to 5 decimal places • Demonstration - http://www.divediscover.whoi.edu/circulation/demonstration.html

36. Wind-Driven Circulation • Wind transfers energy to the water it blows across by the force of friction on the water’s surface • Winds cause both surface currents and waves • Cause horizontal flow of water. • If the wind blows long enough in the same direction, it will cause a water current to develop • What happens if the wind then stops blowing? - The current continues to flow until internal friction, or friction with the sea floor, dissipates its energy

37. Global Wind Patterns

38. Gyres • Gyres: Large system of rotating ocean currents, particularly those involved with large wind movements. • Gyres are caused by the Coriolis Effect • There are five major gyres: • North Atlantic • South Atlantic • North Pacific • South Pacific • Indian

39. Upwelling versus Downwelling Upwelling Downwelling • Upward vertical current that brings deep water to the surface • Tends to bring deepwater nutrients up into the shallow water – increasing biological productivity • Sometimes upwelling occurs when a wind blowing parallel to shore pushes surface water out to sea due to Ekman Transport • Ekman Transport: The net motion of water column down to friction depth • Northern Hemisphere =90o to the right • Southern Hemisphere = 90o to the left • A downward vertical current that pushes surface water deep into the ocean • Carry nutrients and other essential materials out to the deep ocean – have no dramatic effect on biological productivity

41. Upwelling and Downwelling - Deep Ocean e-education.psu.edu

42. Coastal Upwellings and Downwellings eeb.ucla.edu

43. Eddies • Gyres flow in a general area but they don’t flow within perfectly defined paths… they can vary due to wind strength • Eddies: Swirling currents • Caused by friction with adjacent water • Can form large circular loops that can temporarily break away: • Cold–core eddies – flow counter clockwise in the northern hemisphere • Warm-core eddies – flow clockwise in the northern hemisphere • Both types can travel slowly for weeks, months, and even years… • Eddies are important because: • they can affect local temperatures and weather conditions by redistributing heat. • commercial fishing boats use eddies to located fish. • they can affect ship speeds.

44. The Ocean Conveyor Belt • The Ocean Conveyor Belt: The interconnected flow of currents that redistribute heat - AKA the Earth’s Air conditioner • It would take one to two thousand years for a drop of water to complete a cycle on the ocean conveyer belt…

45. Changes in Sea Level • Sea level: the Average level of the sea’s surface at its mean height between high and low tide • Changes in sea level occur in horizontal distances • Ocean circulation causes slopes to develop • Ex. when a land mass interrupts a current’s flow, water mounds up against the land • The slope in the water surface causes a horizontal difference in water pressure • The water will tend to flow out due to this difference creating a pressure gradient • The steeper the mound of water, the larger and faster the current will be

46. sealevel.jpl.nasa.gov

47. Importance of Ocean Circulation • Ocean circulation affects the Earth in many ways: • Circulates nutrients and energy throughout the ocean • Affects the Earth’s climate • Affects the transport and shipping industries. • Transport living things like seeds and actual organisms around the globe.

48. Studying Ocean Currents • Different Approaches: • Lagrangian Method (AKA the Float Method): Studies currents by tracking and drifting an object – floating something in the current that records information as it drifts • Eulerian Method (AKA the Flow Method): Studies currents by staying in one place and measuring the velocity of water as it flows past. • Flotsam Method: Scientists also take advantage of accidental opportunities to study currents… • In 1992 a cargo carrier lost its cargo – 30,000 athletic shoes while en-route to Seattle from Korea. Oceanographers asked the public to report the time, date, and place they found the shoes…. Using this info they were able to improve current models in the north pacific • In 1992 a ship lost 29,000 rubber ducks, frogs, and turtles while sailing from China to Seattle. The toys washed up along the north pacific coast at various location from Oregon to Alaska… eventually drifting through the Bering Strait… they are expected to make it New England… none of washed up yet.

49. Ocean Currents Song • http://safeshare.tv/w/HfLljJafyJ

50. Day 4: Waves • What is a wave? • What are the three types of waves? • What are the crest, trough, height, wavelength, period, and frequency of a wave? • How do wave length and period relate to a wave’s speed? • What disturbing forces cause waves? • What restoring forces resist waves? • Compare shallow water and deep water waves • What three factors affect maximum wave size? • What causes internal waves?