What can you tell me about the increased melting by ash on snow or what
changes it introduces to the albedo.
Mr. Bloch
Hi Mr. Bloch,
I am finally able to give you a partial answer. I got help from Dr.
Thorvaldur Thordarson, a recent PhD graduate from our Department here in
Hawai'i now working in New Zealand:
-
- Immediately I do not remember if there are any papers that deal
specifically with increased melting by ash on snow or what changes it
introduces to the albedo. I will dig into some of my files and see what
I can come up with.
-
From personal experience (i.e., the 1991 Hekla eruption) ash cover in the
range of 1- 5 cm accelerated melting of snow + slight thickness variations
in the ash cover caused differential melting of the suface snow on a local
scale. As a result of that ash (dirt) mounds formed on the surface of the
snow (i.e., cone shaped mounds with a surface cover of ash and core of
snow/ice).
-
Extensive cover of basaltic tephra over snow/glacier covered surface has
to reduce the surface albedo considerably, but maybe not so if the tephra
is light colored rhyolite. I am sure that the glaciology litterature has
something on this subject, because many valley glaciers have very dirty
snouts (lots of dark colored debri on the surface). Someone must have
addressed this issue for melting of + reflectance from glaciers.
-
Sorry that I cannot be of more help to you on this issue - but I will look
into my files + some of the litterature I know of which might address this
problem.
Aloha
Thor
As for the ice sheet business, there is a recent article in EOS,
Transactions, American Geophysical Union, Volume 76, number 27, July 4,
1995 (page 265-270). I can't do the article justice, but it and the
references included in it should be of help to you.
Sincerely,
Scott Rowland, University of Hawaii
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