Download - 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:
• 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 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 onlyWhat are its virtues?
•Simple
•Good reality check
•Can determine age profile vs.
depth
Forward model, diffusion onlyOverview
Measured density profile
Forward model, diffusion onlyOverview
Measured density profile
Calculate porosity and diffusivity
Forward model, diffusion onlyOverview
Measured density profile
Calculate porosity and diffusivity
Tune diffusivity until one species’
observations are reproduced
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 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
Fit to density, used for diffusivity starting-point.
How deep is the diffusive column?
How deep is the diffusive column?
64.84mbs
Getting started with CO2
Correcting for Gravitational Fractionation
Getting started with CO2
After Tuning…
After Tuning…
Testing with other species…
Testing with CH4
Testing with CH3CCl3
Testing with F11
Testing with HFC134a
Summary of basic forward model:
• No big surprises!!!
Summary of basic forward model:
• No big surprises!!!• Density-based diffusivity requires only minor
tweaking
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 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 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 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 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 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?
• Characterizing age spread by depth
Where to next?
• Characterizing age spread by depth• You tell me…