Physical Oceanography OEAS 405/505 Fall 2013

Transcription

1 Physical Oceanography OEAS 405/505 Fall 2013 Instructor: Prof. Tal Ezer Office: CCPO, Innovation Research Park Bldg. # Monarch Way, Room 3217 Office Hours: Tuesday, 9am-11am (or me any time) Telephone Number: address: Class time: Monday, Wednesday, 5:00pm-6:15pm Place: Room 3200, CCPO, Res. 1 Bldg. web page for class:

2 Official Textbook Knauss, 1997: Introduction to Physical Oceanography, Second Edition, Waveland Press. Other useful books- Stewart, 2006 (web): Introduction to Physical Oceanography ( ) Pickard & Emery, 1982: Descriptive Physical Oceanography More advanced- Pond & Pickard, 1983: Introductory Dynamic Oceanography Mellor, 1996: Introduction to Physical Oceanography Other supporting resources will be used such as web resources for online data, journal articles, results from computer models, etc.

3 Grading Homework assignments: 40% Examination #1 ( ): 20% Examination #2 ( ): 20% Final Examination ( ): 20% Assignment must be returned on time (due in one week after assigned) Please type or write clearly If you can not return homework on time due to emergency, send me an before the day its due Follow ODU honor code for student conduct Turn off cell-phone, blackberry, etc

4 Other activities: (not required, but recommended) Seminars: Comp/Eng Bldg (physical oceanography): Mondays 3:30-4:30 (cookies at 3:00) ( ) Rm.200 (phys., biol., chem., geol.): Thursdays 3:00-4:00 (cookies at 4:00) ( )

5 Field trips: Research cruise on the R/V Fay Slover (late October) join OEAS-604 and OEAS-640 classes (if space available).

6 Field trip to see the Omni Globe at the Oceanography/Physics building

7 (1) (2)

8 Schedule (continue ) Book Chapter (3) (4)

9 Why Study Oceanography? More than 70% of earth s surface is covered by water and much of the deep ocean is yet to be explored Large portion of earth s population lives near coasts (build onshore and offshore structures; oil spill impact). Recreation (swimming, diving, boating, surfing ) Transportation. BP oil spill 2010 Source of food (e.g., fishing industry) Source of chemicals & energy. Pollution (e.g., industrial waste carries by ocean currents) Oceans are important for the earth s climate changes Oceans are important for weather (e.g., hurricanes)

10 Disciplines in Oceanography Biological Oceanography Geological Oceanography Oceanography Physical Oceanography Chemical Oceanography However, oceanography becomes more and more an interdisciplinary field

11 Note that oceanographers often interact with scientists from other fields: Atmospheric sciences and meteorology Coastal engineering Fluid dynamics Computer sciences Environmental sciences Even important for political decisions or global economy areas (e.g., policy issues)

12 What is Physical Oceanography? The goal of Physical Oceanography is to obtain a quantitative description of the ocean water and its movement Why? - What?- in order to understand the ocean behavior and allow to predict future changes. Temperature and salt content (and other dissolved substances) Ocean currents and circulation Waves- surface waves, internal waves, tides, tsunamis. Various processes such as mixing (turbulence) Interaction with other components of the earth such as the atmosphere

13 How do we explore and study the ocean? But also with satellites or computer models

14 Approaches in Physical Oceanography Descriptive (or Synoptic) Make observations, diagnose and describe. Try to find logical explanation to what you observed and the relation to other features or theories. Dynamical (or Theoretical) Use known laws of physics and apply them to the ocean (i.e., forces acting on a body), then try to solve mathematical equations ( equation of motion ) to obtain new information on the expected motion under given forces In practice we often combine the two methods:. Example Observation of the thermal gradient offshore of the east coast of the U.S. Why does this occur? Set up the equations to explain. Apply those equations ( model ). Make additional observations and modify the original equations. This may suggest new observations that should be made. - Models may include analytical or numerical (computer) models

15 Techniques in Observation of Motion Eulerian Measuring the flow of water at a given point Example: moored current meter The result is the velocity at point (x 0,y 0,z 0 ) as a function of time V(x 0,y 0,z 0,t) (fig) Lagrangian Tracking a particle by moving with it Example: floats The result is the location of the float as a function of time X(t), Y(t) and sometimes Z(t) (fig)

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17 Sea Surface Temperature (SST) obtained from satellite images

18 Note: Oceans are dynamic and change all the time!

19 History of important expeditions and observational programs James Cook- 3 Pacific Ocean expeditions (Endeavour, Resolution, Discovery) Beagle- South Atlantic & Pacific Oceans Challenger circumnavigated the globe Meteor- Atlantic Ocean International Geophysical Year global International Indian Ocean Expedition 1970s MODE (Mid-Ocean Dynamics Experiment); POLYGON (USSR, Equatorial Atlantic), POLYMODE (US/USSR, Atlantic Ocean) 1990s WOCE (World Ocean Circulation Experiment)- global, start of satellite observations

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26 TOPEX/POSEIDON Satellite Altimeter Sampling

27 Ocean Features and Shapes (separated from oceans or have distinct characteristics) World Map The oceans are basins of salt water on the surface of the solid earth. Their shapes are important for physical oceanography since they affect ocean circulation. Earth: 71% water vs. 29% land Major oceans: Atlantic Ocean, Pacific Ocean, Indian Ocean, Arctic Ocean, Southern Ocean Smaller bodies of water: Mediterranean Sea, Caribbean Sea, Gulf of Mexico, Sea of Japan, etc.

28 How can we project a globe (sphere) into a flat map? There are many different ways!

29 (Cylindrical Equidistant projection)

30 (Robinson projection)

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33 North Pole Distribution of land and sea on earth as a function of latitude Equator South Pole

34 Comparisons of Major Ocean Basins Ocean Atlantic Pacific Indian Area, million sq. km Volume, million cu. km Mean Depth, m Mean Temperature ( C) Mean Salinity ( ) Questions: Why is the Pacific Ocean cooler than the Atlantic and Indian Oceans? Why are the Atlantic and Indian Oceans saltier than the Pacific Ocean?

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36 The general pattern of winds over the globe and the expected gyres circulation

37 But ocean circulation is much more complex. Why?

38 Ocean circulation is complex as a result of many parameters such as winds, the shape of each basin, earth rotation, airsea interaction, etc. (Physical Oceanographers aim to understand them) Pacific Ocean Atlantic Ocean