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Modeling Tides for Southern Ocean GLOBEC

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

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Modeling Tides for Southern Ocean GLOBEC

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  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 1/4o E/W and 1/12o N/S (~10 km at 70oS). Forced by height fields along 58oS obtained from the Oregon State University TPXO5.1 global tidal solution.

  5. CATS Model Domain

  6. 2-D Model: CATS Resolution: The resolution is 1/4o E/W and 1/12o N/S (~10 km at 70oS). Forced by height fields along 58oS obtained from the Oregon State University TPXO5.1 global tidal solution. Bathymetry: modified ETOPO-5. Constituents: K1,O1,P1,Q1, M2,S2,N2,K2,Mm,Mf.

  7. K1 M2

  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 1/8o E/W and 1/15o 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 1/8o E/W and 1/15o N/S (~8 km). Forced by normal flow at open boundaries (taken from CATS). Bathymetry: modified ETOPO5. Constituents: K1 and M2, modeled separately.

  14. K1 K1

  15. M2 Adelaide Island

  16. K1 Adelaide Island

  17. M2 Adelaide Island

  18. M2 M2

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

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