1. Surface and bottom topography of the oceans

2. How do we measure seafloor topography? Why is ocean bathymetry important? Questions:

3. What does it mean to be at an altitude of 4000m? It means that I am 4000m above the Mean Sea Level (MSL) Then, what sets the mean sea level ?

4. Geoid of a rotating tank Geoid = the shape of mean sea level Centrifugal force pulls up the surface away from the axis of rotation Parabolic surface Apparent gravity is perpendicular to the tilted surface

5. Geoid on a spherical planet Centrifugal force bulges out the surface away from the axis of rotation Geoid ≈ ellipsoid Apparent gravity is deflected outward The Earth’s geoid has irregularities due to spatially varying gravity (shape) of the planet

6. Geoid reflects seafloor topographic features

7. What sets the Earth’s geoid? 1. The spin of the planet  Ellipsoid 2. Irregular seafloor topography  Local changes in gravity

8. Measuring seafloor from space Reading material on Class Website “Satellite Topography and Oceanography from Space”

9. Satellite can measure the height of ocean surface very accurately The shape of surface ocean reflects spatially varying gravity of the planet Seafloor topography can be calculated based on the irregularity of gravity field

10. Why ocean bathymetry? Tsunami prediction Ocean current, climate studies Offshore resource development Submarine cables for telecommunication International boundaries

11. Ocean Circulation and Climate Heat Transport affected by topography!

12. Ocean Circulation and Climate Ocean Currents take different paths!

13. Ocean Circulation and Climate Deep ocean mixing and pathways

14. Ocean Circulation and Climate Mixing energy and dissipation of tides!

15. Ocean Circulation and Biology Seamounts ….

16. Societal impacts Tsunami

17. Societal impacts Gas and oil extraction