1. Modeling Tides for Southern Ocean GLOBEC Susan Howard and Laurence Padman Earth & Space Research

2. Motivation Tidal currents are “noise” in ship ADCP records. A model helps us remove them to highlight the mean circulation. Tides contribute to benthic stirring and pycnocline mixing. Ocean-applied stresses on the sea-ice base affect ice kinematics and surface buoyancy exchanges.

3. Topics 2-D model Description of model Results Validation 3-D model (preliminary work): Description of model Results

4. 2-D Model: CATS Resolution: The resolution is 1/4 o E/W and 1/12 o N/S (~10 km at 70 o S). Forced by height fields along 58 o S obtained from the Oregon State University TPXO5.1 global tidal solution.

5. CATS CATS Model Domain

6. 2-D Model: CATS Resolution: The resolution is 1/4 o E/W and 1/12 o N/S (~10 km at 70 o S). Forced by height fields along 58 o S obtained from the Oregon State University TPXO5.1 global tidal solution. Bathymetry: modified ETOPO-5. Constituents: K 1,O 1,P 1,Q 1, M 2,S 2,N 2,K 2,M m,M f.

7. K1K1 M2M2

8. CATS Model Mean tidal speed 10 Constituents Weak tides except at shelf break Tides at shelf break diurnal (TVW) Currents will be affected by bathymetry

9. Tidal Signal in Drifters Max speeds 15 cm s -1 Diurnal band only Speed varies with position & spring neap cycle Evidence of strong tides near shelf break

10. CATS vs. Moorings

11. 3-D Model: POM Resolution: The resolution is 1/8 o E/W and 1/15 o N/S (~8 km). (we want to work toward a 2-4 km res.) Forced by normal flow at open boundaries (taken from CATS).

12. POM Model Domain (preliminary)

13. 3-D Model: POM Resolution: The resolution is 1/8 o E/W and 1/15 o N/S (~8 km). Forced by normal flow at open boundaries (taken from CATS). Bathymetry: modified ETOPO5. Constituents: K 1 and M 2, modeled separately.

14. K1K1 K1K1

15. Adelaide Island M2M2

16. K1K1

17. M2M2

18. M2M2 M2M2

19. Conclusions Tidal currents are quite weak except at the shelf break. Internal tides may be generated by both diurnal and semidiurnal flows across the upper continental slope. Surface tidal currents move the ice pack around, and may also increase open- water fraction. Lots of room for model improvements!

20. CATS Model Improvements Rerun Cats with New WHOI Bathymetry Improve resolution Update internal tide dissipation parameterization Assimilate BPR and coastal tide gauge data

21. POM Model Improvements Use new WHOI bathymetry Increase resolution Increase domain size Use spatially varying stratification Examine seasonal effects of stratification Improve open boundary conditions

22. Acknowledgements We would like to thank Dick Limeburner for providing us with drifter data and Lana Erofeeva for help with tide modeling.