Modeling air movement in the firn at wais d
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Modeling Air Movement in the Firn at WAIS-D. Mark Battle Bowdoin College. WAIS-D meeting NICL July 16, 2006. Possible firn modeling strategies:. Forward model, diffusion only ( Schwander etc. ) Inverse model, diffusion only ( Butler et al.1999)

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Modeling Air Movement in the Firn at WAIS-D

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Modeling air movement in the firn at wais d

Modeling Air Movementin the Firn at WAIS-D

Mark Battle

Bowdoin College

WAIS-D meeting

NICL

July 16, 2006


Possible firn modeling strategies

Possible firn modeling strategies:

  • Forward model, diffusion only (Schwander etc.)

  • Inverse model, diffusion only (Butler et al.1999)

  • Inverse model, diffusion only, a’la Rommelaire

  • Forward model, diffusion & heat (Severinghaus et al. 2000 )

  • Forward model, diffusion & close-off fractionation (Severinghaus & Battle, 2005 )

  • Other approaches?


Possible firn modeling strategies1

Possible firn modeling strategies:

  • Forward model, diffusion only(Schwander etc.)

  • Inverse model, diffusion only (Butler et al.1999)

  • Inverse model, diffusion only, a’la Rommelaire

  • Forward model, diffusion & heat (Severinghaus et al. 2000 )

  • Forward model, diffusion & close-off fractionation (Severinghaus & Battle, 2005 )

  • Other approaches?


Forward model diffusion only what are its virtues

Forward model, diffusion onlyWhat are its virtues?

  • Simple

  • Good reality check

  • Can determine age profile vs. depth


Forward model diffusion only overview

Forward model, diffusion onlyOverview

Measured density profile


Forward model diffusion only overview1

Forward model, diffusion onlyOverview

Measured density profile

Calculate porosity and diffusivity


Forward model diffusion only overview2

Forward model, diffusion onlyOverview

Measured density profile

Calculate porosity and diffusivity

Tune diffusivity until one species’ observations are reproduced


Forward model diffusion only overview3

Forward model, diffusion onlyOverview

Measured density profile

Calculate porosity and diffusivity

Tune diffusivity until one species’ observations are reproduced

Confirm(?) with other species


Forward model diffusion only overview4

Forward model, diffusion onlyOverview

Measured density profile

Calculate porosity and diffusivity

Tune diffusivity until one species’ observations are reproduced

Confirm(?) with other species

Use it


Field measured density in various cores at wais d

Field-measured density in various cores at WAIS-D


Fit to density used for diffusivity starting point

Fit to density, used for diffusivity starting-point.


How deep is the diffusive column

How deep is the diffusive column?


How deep is the diffusive column1

How deep is the diffusive column?

64.84mbs


Getting started with co 2

Getting started with CO2


Correcting for gravitational fractionation

Correcting for Gravitational Fractionation


Getting started with co 21

Getting started with CO2


After tuning

After Tuning…


After tuning1

After Tuning…


Testing with other species

Testing with other species…


Testing with ch 4

Testing with CH4


Testing with ch 3 ccl 3

Testing with CH3CCl3


Testing with f11

Testing with F11


Testing with hfc134a

Testing with HFC134a


Summary of basic forward model

Summary of basic forward model:

  • No big surprises!!!


Summary of basic forward model1

Summary of basic forward model:

  • No big surprises!!!

  • Density-based diffusivity requires only minor tweaking


Summary of basic forward model2

Summary of basic forward model:

  • No big surprises!!!

  • Density-based diffusivity requires only minor tweaking

  • XX vs. depth looks generally good for wide range of histories


Summary of basic forward model3

Summary of basic forward model:

  • No big surprises!!!

  • Density-based diffusivity requires only minor tweaking

  • XX vs. depth looks generally good for wide range of histories

  • “Gravitational” correction needs more data


Summary of basic forward model4

Summary of basic forward model:

  • No big surprises!!!

  • Density-based diffusivity requires only minor tweaking

  • XX vs. depth looks generally good for wide range of histories

  • “Gravitational” correction needs more data

  • DCH3CCl3/DCO2 consistent with SPO


Summary of basic forward model5

Summary of basic forward model:

  • No big surprises!!!

  • Density-based diffusivity requires only minor tweaking

  • XX vs. depth looks generally good for wide range of histories

  • “Gravitational” correction needs more data

  • DCH3CCl3/DCO2 consistent with SPO

  • DF11/DCO2 consistent with theory (and not SPO)


Summary of basic forward model6

Summary of basic forward model:

  • No big surprises!!!

  • Density-based diffusivity requires only minor tweaking

  • XX vs. depth looks generally good for wide range of histories

  • “Gravitational” correction needs more data

  • DCH3CCl3/DCO2 consistent with SPO

  • DF11/DCO2 consistent with theory (and not SPO)

  • Timing of forcing history crucial (e.g. HFC134a)


Summary of basic forward model7

Summary of basic forward model:

  • No big surprises!!!

  • Density-based diffusivity requires only minor tweaking

  • XX vs. depth looks generally good for wide range of histories

  • “Gravitational” correction needs more data

  • DCH3CCl3/DCO2 consistent with SPO

  • DF11/DCO2 consistent with theory (and not SPO)

  • Timing of forcing history crucial (e.g. HFC134a)

  • Ready to roll…


Where to next

Where to next?

  • Characterizing age spread by depth


Where to next1

Where to next?

  • Characterizing age spread by depth

  • You tell me…


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