1 / 38

Olivier Marchal Woods Hole Oceanographic Institution Roger Francois

An Inverse Method to Combine of 230 Th Data and a Circulation Model: Application to the North Atlantic. Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory, Monaco.

erin-hudson
Download Presentation

Olivier Marchal Woods Hole Oceanographic Institution Roger Francois

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. An Inverse Method to Combine of 230Th Data and a Circulation Model: Application to the North Atlantic Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory, Monaco Thanks to Carl Wunsch (MIT)

  2. 230Th • Half-life = 76 kyr • In ocean waters: 230Th/234U = O(10-4)

  3. b

  4. unfiltered samples filtered samples CENTRAL NORTH PACIFIC 23oN, 158oW r2 = 0.99 (n=8) Data: Roy-Barman et al. (EPSL, 1996)

  5. SUBANTARCTIC ZONE 47oS, 142oE filtered samples r2 = 0.99 (n=12) Data: R. Francois (pers. comm.)

  6. SOME STATIONS WITH DISSOLVED 230Th MEASUREMENTS Data: R. Francois (pers. comm.)

  7. DISSOLVED 230Th IN NORTH ATLANTIC Data: R. Francois (pers. comm.)

  8. QUESTION Can 230Th data complement physical oceanography data?

  9. STRATEGY Use of an inverse method to assess dynamical information in 230Th data: • Inversion # 1: Hydrographic data + circulation model • Inversion # 2: Hydrographic data + circulation model + 230Th

  10. MODEL GRID HORIZONTAL SPACING: 3o x 3o VERTICAL LEVELS: 1000 m 2000 m 3000 m 4000 m 5000 m Total 230Th Dissolved 230Th

  11. INVERSION # 1 HYDROGRAPHIC DATA + CIRCULATION MODEL

  12. HYDROGRAPHIC DATA

  13. CIRCULATION MODEL

  14. = 0 Tarantola & Valette (1982) Mercier (1986)

  15. HORIZONTAL FLOW BETWEEN 1000-4000 m Ui + Vj ERRORS IN (U,V)

  16. HORIZONTAL FLOW BETWEEN 4000-5000 m Ui + Vj ERRORS IN (U,V)

  17. INVERSION # 2 HYDROGRAPHIC DATA + CIRCULATION MODEL + 230Th

  18. 230Th MODEL

  19. SED. SED. SED. (n = 75) Mean FRACTION OF 230Th IN PARTICULATE FORM (K = Cp/C) Cochran et al. (EPSL, 1987) Colley et al. (DSR, 1995) Moran et al. (EPSL, 1997, 2002) Vogler et al. (EPSL, 1998)

  20. EFFECT OF 230Th IN ESTIMATION OF INTEGRATED TRANSPORTS

  21. EFFECT OF 230Th IN ESTIMATION OF INTEGRATED TRANSPORTS

  22. WHY DO 230Th LEAD TO HIGHER ESTIMATES OF VOLUME TRANSPORT?

  23. r – 1000 (kg/m3) < 41.66 41.66 > 41.66 IN SITU DENSITY AT 3000 m IN NORTH ATLANTIC C.I. = 0.02 kg/m3 Data: HydroBase2 (R. Curry)

  24. u = 0 is a possible solution

  25. u = 0 is NOT a possible solution unless C(z) is linear

  26. CONCLUSIONS Yes, 230Th data can complement physical oceanography data • In 1st inversion (230Th data not considered), the flow displays a WBC and coherent structures in the interior with low statistical significance • In 2nd inversion, the flow is further constrained by 230Th data: - Addition of 230Th leads to the estimation of a larger amplitude of the integrated meridional transports below 1000 m (by 2-9 Sv) - Correction by 230Th for a tendency of inverse geostrophic models to lead to the inference of a vanishing flow when horizontal r gradients are insignificant

  27. PENDING QUESTIONS • How comparable are 230Th data generated in different laboratories? • How do particle fluxes and composition influence Th scavenging? - Need for 230Th measurements on both dissolved and particulate phases (K) - Need for Th scavenging experiments with various particle types (e.g., Chase et al., 2002) • Should we aim for more sophisticated scavenging models?

  28. COMPARISON BETWEEN INTEGRATED TRANSPORTS Roemmich & Wunsch (1985) Bryden et al. (2005) Roemmich & Wunsch (1985)

  29. EFFECT OF 230Th IN ESTIMATION OF INTEGRATED TRANSPORTS Error in radiochemical balance: <eC2>1/2 = 0.75 x 105 dpm s-1

  30. FLOAT TRAJECTORIES Data from Hogg and Owens (1999)

  31. Floats Theory Marchal and Nycander (J. Phys. Oceanogr., 2004)

  32. MODEL GRID HORIZONTAL SPACING: 3o x 3o VERTICAL LEVELS: 1000 m 2000 m 3000 m 4000 m 5000 m Total 230Th Dissolved 230Th

  33. DATA & MODEL RESIDUALS

  34. INVERSION # 2: DENSITY AND 230Th • x0 extended to include 230Th • C0 extended to include 230Th errors

  35. DATA & MODEL RESIDUALS

  36. (w* = Kws = 115 m yr-1)

More Related