date: Fri, 16 Jul 2004 11:07:05 +0100
from: Sarah Raper <sraper@awi-bremerhaven.de>
subject: Re: next
to: Tom Wigley <wigley@cgd.ucar.edu>


On 15 Jul 2004, at 13:41, Tom Wigley wrote:

> Sarah,
>
> I will cover the new points and add the refs. They are
> important in case we get some of these authors as
> reviewers. It is hard to add text specifically to knock
> the TAR method. One problem is that it should be
> a differential equation at the outset. My addition changes
> it to a differential equation -- but in a rather roundabout
> way. The reason that the TAR method is OK is that
> if the time scale is >> 100 years (as it seems to be) then
> the d/dt term drops out. Praps I can add a little bit about
> this at the end.
>
> What is annoying to me is that the TAR method is
> conceptually flawed and it happens to work not becoz of
> cleverness and forward thinking by Jonathan, but by a
> fluke.
>
> Oh well.

EXACTLY! As you say never mind.
>
> Jane Leggett, who is funding some of my MAGICC work,
> wondered about sensitivity proportional to remaining
> V instead of A. To test this I can use proporional to V**n
> for different 'n'.. Then we could cite the J. Glac. paper too.
> This is only one line of code.
>
> What 'n' range?

I used this but the better reference is probably

Bahr, D. B., Meier, M.F., and Peckham, S.D.;1997 The Physical Basis of 
Glacier Volume-Area scaling.  J. Geophys. Res 102 20355-20362.

 From memory they find V=A**alfa where alfa is 1.36 for glaciers and 
1.25 for icecaps. The original data for the glacier part comes from 
Ohmura and Chen I will try to send you the graph and if I can get the 
pdf I will also send you that.

In the J. Glac paper I used 1/1.36 = 0.735 in A=V**0.735. FOR GLACIER

Will look in paper for n range but for this purpose we combine glacier 
and icecaps don't we.


>
> Here is what I said to Jane .....
>
> ------------------
>
>> The linear with volume vs linear with area is something I will look 
>> into. There
>> is a paper that Sarah is first author on in J. Glaciology a few years 
>> back where
>> we note that one can use A = V**n. I can put this in the code to see 
>> the
>> sensitivity to 'n'. My intuition says it will be small. To 2100, 
>> volume has no
>> effect, so 'n' cannot be important. For large times the paths must 
>> tend to the
>> initial volume, so 'n' can have no effect there either. Still, it is 
>> easy to do the
>> full sums to check this out. Good point.
>
>
> ----------------------------
>
> Tom.
>
>

