GLIMS definition issues

Tue Aug 28 16:02:43 MDT 2001

Hi Bruce:

Thanks for the e-mail message.  I also received related e-mails from Hugh
Kieffer, John Dwyer, and Jeff Kargel.  My reply is directed at the request
for definitions:

1. Definition of a glacier.

Here is what Mark Meier has to say in the 15th edition of the Encyclopedia
Britannica (1974, p. 175):

"A glacier may be defined as a large mass of perennial ice that originates
on land by the recrystallization of now or other forms of solid
precipitation and that shows evidence of past or present flow.  The
definition is not precise, because exact limits for the terms large,
perennial, and flow cannot be set.  Except in terms of size, a small snow
patch that persists for more than one season is hydrologically
indistinguishable from a true glacier.  One international group has
recommended that all persisting snow and ice masses larger than 0.1 square
kilometer (about 0.04 square mile) be counted as glaciers.  Hence in the
absence of an agreed-upon upper size limit for glaciers, a body of ice as
large as the Antarctic Ice Sheet could properly be considered a glacier."

The Illustrated Glossary of Snow and Ice (Scott Polar Research Institute
Special Publication No. 4) by Armstrong and others, 1973, gives the
following definition for a glacier on p. 17

"A mass of snow and ice continuously moving from higher to lower ground or,
if afloat, continuously spreading.  The principal forms of glaciers are:
ice sheets, ice shelves, ice caps, ice piedmonts, and various types of
mountain glacier."

UNESCO (1970) and Muller and others (1977) listed 9 types of glaciers in
their glacier classification and description:

Continental ice sheet
Ice field
Ice cap
Outlet glacier
Valley glacier
Mountain glacier
Glacieret and snowfield
Ice shelf
Rock glacier

They also listed another category that that showed as Uncertain or
miscellaneous.

2. How to treat ice shelves.

Ice shelves should be treated as a floating ice sheet.  An ice shelf is a
specific type or form of glacier.

Armstrong and others (1973, p. 26) define an ice shelf as follows:

"A floating ice sheet of considerable thickness attached to a coast.  Ice
shelves are usually of great horizontal extent and have a level or gently
undulating surface.  They are nourished by the accumulation of snow and
often by the seaward extension of land glaciers.  Limited areas my be
aground.  The seaward edge is termed an ice front."

3. Coordinate systems.

The World Glacier Inventory Project, now part of the World Glacier
Monitoring Service, published an "Instructions for Compilation and
Assemblage of Data for a World Glacier Inventory" in 1977 (Muller and
others, 1977).  It provides a digital data base system for classifying
glaciers and their form and providing other glaciological information.  The
Standard Data Sheet has entries for both latitude and longitude coordinates
and UTM coordinates.  I frankly prefer UTM coordinates, because one can
accurately pinpoint very small glaciers easily under the UTM coordinate
system.  Latitude and longitude coordinates descend from degrees to minutes
to seconds or fractions of seconds to achieve the accurate geographic
location.  Of course, with computers it is relatively easy to transform
between different coordinate systems.  I recommend using UTM coordinates.

I hope that the above is of help to you.  Please let me know if I can be of
further assistance.

Best regards,

Richie

 Richard S. Williams, Jr.
 Research Geologist-ST

U.S. Geological Survey
Woods Hole Field Center
384 Woods Hole Road
Woods Hole, MA 02543-1598 U.S.A.

Tel: 508-457-2347
Fax: 508-457-2310
e-mail: rswilliams at usgs.gov

"... it is to try to understand, to add a little more to human knowledge.  That is the mission of the
researcher ... Rejection of ignorance, the desire to know and explain are, I think, the honor and
glory of the human mind."
                              Theodore Monod, French scientist (1902-2000)

                    Bruce Raup                                                                      
                    <braup at nsidc.        To:     GLIMS Database mailing list                        
                    org>                 <glims_database at flagmail.wr.usgs.gov>, GLIMS Parameters    
                                         mailing list <glims_param at flagmail.wr.usgs.gov>,           
                    08/24/01             <jferrign at oemg.er.usgs.gov>, <rswilliams at usgs.gov>         
                    04:07 PM             cc:                                                        
                                         Subject:     Re: GLIMS definition issues                   

On 2001-08-24 11:36 -0500,  John L Dwyer wrote:

> See the attached file (if you can read a Powerpoint slide) that shows
> how well the geometry and georeferencing of an ASTER Level-1B product
> compares with a map-overlay.  I would consider either re-writing this

John's attachment was too large for our list configuration, so it bounced.
You can now see the two slides at the glims_database scratch site:

http://spot.colorado.edu/~braup/glims_database/

Bruce

--
Bruce Raup
National Snow and Ice Data Center                     Phone:  303-492-8814
University of Colorado, 449 UCB                       Fax:    303-492-2468
Boulder, CO  80309-0449                                    braup at nsidc.org