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SUMMARY:Ablation -and maybe growth - at the base of floating ice sheets - 
 D. Hatton\, ITG
DTSTART:20090514T103000Z
DTEND:20090514T113000Z
UID:TALK18215@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Changes in the extent and volume of sea ice can disrupt region
 al and  global temperature\, alter ocean circulation\, and affect sensitiv
 e  ecosystems.  Therefore\, it is important to understand the physics by  
 which sea ice ablates (or grows) at its base.  Theoretical modelling  of t
 his process is a very well-studied problem\, and we take as a  starting po
 int a model from the literature\, based on phase equilibrium  at the ice/f
 luid interface\; heat balance between turbulent transport  in fluid\, cond
 uctive transport in ice\, and latent heat consumption in  ablation\; and s
 alt balance between turbulent transport in fluid and  salt consumption in 
 ablation.  The model uses a linear temperature  profile in the ice\, meani
 ng conductive heat transport inversely  proportional to ice thickness.  Th
 is makes thin ice tend to grow and  thick ice tend to ablate.  We note pro
 perties of the model not  emphasized in the literature: the thickness-depe
 ndence of heat  transport gives ice a surprisingly small equilibrium thick
 ness\, which  it approaches on a surprisingly rapid relaxation timescale. 
  We  suggest a refinement to the model\, based on the idea that the ice ba
 se  has imperfect information about the thickness of ice above it\, which 
  brings the model into closer agreement with field data on ablation  rates
 .  We note\, however\, that neither the original nor the refined  model ca
 n fully explain how ice of typical field thicknesses grows. We  speculate 
 on the possibility that\, at certain times\, diffusive  transport dominate
 s over turbulent transport in the fluid\, and on  whether this can explain
  the growth of thick ice.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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