[GLIMS] Book chapter

[Wilfried Haeberli]

Thanks, Roger.

This is a fine contribution.

I especially appreciate that Figure 8.5 is a plot of mean *thickness versus
area *and not *volume versus area* (which would contain area in both axes
and hence seemingly suppress the scatter in the relation between the
originally measured variables thickness and area).

The data presentation in Figure 8.5 immediately shows that the uncertainty
in thickness - and hence volume - estimates from area is at least a factor
of 2 if not more. In addition to this very large uncertainty, area-related
thickness/volume estimates also contain the sometimes large uncertainty
about ill-defined areas and an unfortunate error propagation of the area
uncertainty in thickness/volume estimates. Moreover, the increasingly often
observed disintegration of glaciers into smaller pieces introduces
important artifacts concerning area-related thickness/volume estimates: in
the very moment the last ice crystal joining two glaciers melts the
thickness and hence total volume of the now 2 glaciers immediately becomes
smaller, because the estimated thickness of the two now separated and
smaller glaciers is smaller.

I think that we should still more critically reflect area-related
thickness/volume estimates. There have been good and well reflected reasons
to go away from such approaches already many years ago. First, area is not
really the primary factor influencing ice thickness but (in addition to the
mass balance gradient) elevation range and slope (which are available from
detailed glacier inventories). Second, we now have high-resolution digital
terrain information which opens a new dimension of local (rather than
average) ice thickness estimates and reconstruction of detailed glacier bed
topography. No need any more to limit our analysis to average thickness and
total volume. I think that this has become clear to many of us and should
be adequately mentioned.

Kind regards and very best wishes.

Wilfried




On Tue, Dec 6, 2011 at 6:25 PM, Roger Barry <rbarry at nsidc.org> wrote:

> FYI
> A chapter I reviewed
> Roger
>
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-- 
--
Wilfried Haeberli
Department of Geography / University of Zurich
Winterthurerstrasse 190 / CH - 8057 Zurich
Phone: +41/(0)44/635 51 20 / Fax: +41/(0)44/635 68 41
e-mail: wilfried.haeberli at geo.uzh.ch
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