1. Physical Oceanography SACS/AAPT Spring Meeting March 29, 2003 Coastal Carolina University

2. What is Physical Oceanography? Physics applied to the oceans…… Properties and Motion of Seawater, including: Density, Pressure, Temperature Waves, Tides Global Heat Fluxes Equations of Motion (Newton’s 2 nd Law Applied to water…)

3. It’s how you explain this:

4. Equations of Motion (Newton’s 2 nd Law applied to water) Oceanographers like to consider the force per volume of water: Of course, oceanographers never write out F/V, it’s just understood:

5. Coordinate System Used for all calculations from now on….

6. Forces on a Parcel of Water Gravity Coriolis Pressure Friction

7. Coriolis “Force” This apparent (or pseudo) force exists because we all live on an accelerating reference frame (a rotating planet). Since our coordinate system is rotating with the planet, it is indistinguishable from a ‘real’ force, and we will treat it as such. Coriolis Force Simulation

8. Coriolis “Force” Coriolis force = m f (speed) m = mass of water parcel f = Coriolis parameter = 2  sin(  )  = Earth’s angular velocity  = latitude Remembering that Oceanographers like their forces per volume:

9. Pressure Gradient A Pressure Gradient is a measure of how the pressure is changing as you move in the horizontal direction. It is simply: What are its units? How is this a force?

10. Why this is a force: Force between 1 and 2: But we want force per volume…..

11. What happens then? Because of this force, fluids move from areas of high pressure towards areas of low pressure:

12. How do you get a pressure gradient in the water?

13. How do you measure  P? (i is the surface slope)

14. Equations of Motion Coming back to the x and y equations of motion:

15. Geostrophic Balance If: Only important forces are Pressure Gradient and Coriolis Ocean is in “Steady State” (no acceleration)

16. Geostrophic Balance (2) or

17. Geostrophic Current: Which way does the current flow if the surface height is increasing towards the South? West? North?

18. Dynamic Topography

19. Geostrophy Movie

20. Gulf Stream

21. Quiz 1: Which direction does the water flow around this pressure feature if it is in the Northern Hemisphere? Counter-Clockwise Cyclonic

22. Quiz 2: Which direction does the water flow around this pressure feature if it is in the Southern Hemisphere? Counter-Clockwise Cyclonic ? NO….anti-cyclonic