olivier marchal woods hole oceanographic institution roger francois earth and ocean sciences, u....
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![Page 1: Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory,](https://reader035.vdocuments.site/reader035/viewer/2022081514/56649d435503460f94a1ef57/html5/thumbnails/1.jpg)
Olivier MarchalWoods Hole Oceanographic Institution
Roger FrancoisEarth and Ocean Sciences, U. British Columbia
Jan ScholtenMarine Environment Laboratory, Monaco
An Inverse Method to Combine of 230Th Data and a Circulation Model:
Application to the North Atlantic
Thanks to Carl Wunsch (MIT)
![Page 2: Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory,](https://reader035.vdocuments.site/reader035/viewer/2022081514/56649d435503460f94a1ef57/html5/thumbnails/2.jpg)
• Half-life = 76 kyr
• In ocean waters: 230Th/234U = O(10-4)
230Th
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CENTRAL NORTH PACIFIC 23oN, 158oW
Data: Roy-Barman et al. (EPSL, 1996)
r2 = 0.99 (n=8)
unfiltered samples
filtered samples
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SUBANTARCTIC ZONE 47oS, 142oE
r2 = 0.99 (n=12)
Data: R. Francois (pers. comm.)
filtered samples
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SOME STATIONS WITH DISSOLVED 230Th MEASUREMENTS
Data: R. Francois (pers. comm.)
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DISSOLVED 230Th IN NORTH ATLANTIC
Data: R. Francois (pers. comm.)
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Can 230Th data complement physical oceanography data?
QUESTION
![Page 9: Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory,](https://reader035.vdocuments.site/reader035/viewer/2022081514/56649d435503460f94a1ef57/html5/thumbnails/9.jpg)
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
STRATEGY
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MODEL GRID
Total 230Th
Dissolved 230Th
HORIZONTAL SPACING:
3o x 3o
VERTICAL LEVELS:
1000 m2000 m3000 m4000 m5000 m
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INVERSION # 1
HYDROGRAPHIC DATA + CIRCULATION MODEL
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HYDROGRAPHIC DATA
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CIRCULATION MODEL
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= 0
Tarantola & Valette (1982)Mercier (1986)
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HORIZONTAL FLOW BETWEEN 1000-4000 m
ERRORS IN (U,V)
Ui + Vj
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HORIZONTAL FLOW BETWEEN 4000-5000 m
ERRORS IN (U,V)
Ui + Vj
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INVERSION # 2
HYDROGRAPHIC DATA + CIRCULATION MODEL + 230Th
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230Th MODEL
![Page 19: Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory,](https://reader035.vdocuments.site/reader035/viewer/2022081514/56649d435503460f94a1ef57/html5/thumbnails/19.jpg)
FRACTION OF 230Th IN PARTICULATE FORM (K = Cp/C)
SED.
SED.
SED.
Mean 01.015.0K (n = 75)
Cochran et al. (EPSL, 1987)Colley et al. (DSR, 1995)Moran et al. (EPSL, 1997, 2002)Vogler et al. (EPSL, 1998)
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EFFECT OF 230Th IN ESTIMATION OF INTEGRATED TRANSPORTS
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EFFECT OF 230Th IN ESTIMATION OF INTEGRATED TRANSPORTS
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WHY DO 230Th LEAD TO HIGHER ESTIMATES OF VOLUME TRANSPORT?
![Page 23: Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory,](https://reader035.vdocuments.site/reader035/viewer/2022081514/56649d435503460f94a1ef57/html5/thumbnails/23.jpg)
IN SITU DENSITY AT 3000 m IN NORTH ATLANTIC
– 1000 (kg/m3)
< 41.66 41.66> 41.66
C.I. = 0.02 kg/m3
Data: HydroBase2 (R. Curry)
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u = 0 is a possible solution
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u = 0 is NOT a possible solution unless C(z) is linear
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CONCLUSIONS
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 gradients are insignificant
Yes, 230Th data can complement physical oceanography data
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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?
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COMPARISON BETWEEN INTEGRATED TRANSPORTS
Roemmich & Wunsch (1985)
Bryden et al. (2005)
Roemmich & Wunsch (1985)
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Error in radiochemical balance: <C
2>1/2 = 0.75 x 105 dpm s-1
EFFECT OF 230Th IN ESTIMATION OF INTEGRATED TRANSPORTS
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FLOAT TRAJECTORIES
Data from Hogg and Owens (1999)
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Marchal and Nycander (J. Phys. Oceanogr., 2004)
Floats
Theory
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MODEL GRID
Total 230Th
Dissolved 230Th
HORIZONTAL SPACING:
3o x 3o
VERTICAL LEVELS:
1000 m2000 m3000 m4000 m5000 m
![Page 35: Olivier Marchal Woods Hole Oceanographic Institution Roger Francois Earth and Ocean Sciences, U. British Columbia Jan Scholten Marine Environment Laboratory,](https://reader035.vdocuments.site/reader035/viewer/2022081514/56649d435503460f94a1ef57/html5/thumbnails/35.jpg)
DATA & MODEL RESIDUALS
i,o
i,oi
c
xx.r.n
i,f
i
c
)x(f.r.n
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INVERSION # 2: DENSITY AND 230Th
• x0 extended to include 230Th
• C0 extended to include 230Th errors
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DATA & MODEL RESIDUALS
i,o
i,oi
c
xx.r.n
i,f
i
c
)x(f.r.n
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(w* = Kws = 115 m yr-1)