

NASA Data Reveals Mega-Canyon under Greenland Ice Sheet - olefoo
http://www.nasa.gov/content/goddard/nasa-data-reveals-mega-canyon-under-greenland-ice/#.Uh_YCWSe_Iw

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ovis
I wonder how much this new map will effect model predictions of ice velocity
and dynamic mass balance. Ice thickness measurements are important for
calculating the stresses required to model ice velocity, and these are in turn
relevant to predictions for the ice sheet's future because they affect how the
ice might respond, for example, to increased melting at either the surface or
coastal margins.

I would also be interested in seeing simple calcs of hydraulic potential with
the new bed geometry. I wonder if water is still routed along this canyon?

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madaxe
Almost certainly. They even say so in the article. Most glacial melt flow is
subsurface - disappears down a moulin and flows out under the overhanging
shelf, accelerating melt. Feedbacktastic.

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ovis
This is true.

Ah ha! Much more detail here:
[http://www.sciencemag.org/content/341/6149/997.full](http://www.sciencemag.org/content/341/6149/997.full)

Seems that in some parts of the upper canyon, the ice configuration likely
leads water away, but in the lower part, it controls the direction of water
flow.

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acjohnson55
It blew my mind to learn a couple weeks ago that many scientists believe that
Greenland is actually three separate major islands that together hold up the
icecap.
[http://news.google.com/newspapers?nid=860&dat=19511024&id=pW...](http://news.google.com/newspapers?nid=860&dat=19511024&id=pWwKAAAAIBAJ&sjid=xEoDAAAAIBAJ&pg=5335,4712968)

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jmadsen
Says at the end that "it may play a major role in transporting melt
water...into the Arctic Ocean"

Seems to me, we just need to dynamite it shut and _Presto_ world saved from
eventual catastrophic flooding.

Don't everyone thank me at once.

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Gravityloss
No, we must _nuke it_.

~~~
yk
Somebody call Bruce Willis.

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U2EF1
Just think, within our lifetimes we'll be able to explore this canyon by foot.

~~~
ddeck
Perhaps with some deep sea diving gear. The surface of Greenland's bedrock is
close to sea level in the interior and the discovered canyon appears to in the
area that is below sea level.[1]

In addition, it's estimated that a complete melting of the ice sheet would
increase sea levels by ~24ft[2] and that's not taking into account the larger
impact of the rest of the world melting (Antarctic ice sheet is much larger).

[1]
[http://commons.wikimedia.org/wiki/File:Topographic_map_of_Gr...](http://commons.wikimedia.org/wiki/File:Topographic_map_of_Greenland_bedrock.jpg)

[2]
[http://en.wikipedia.org/wiki/Greenland_ice_sheet](http://en.wikipedia.org/wiki/Greenland_ice_sheet)

~~~
nfg
You're not accounting for rebound: [http://en.wikipedia.org/wiki/Post-
glacial_rebound](http://en.wikipedia.org/wiki/Post-glacial_rebound).

~~~
ddeck
True, but that would need to be some kind of rebound ;).

Even ignoring sea level rises due to ice loss elsewhere and the fact that the
area we're discussing already appears well below sea level, the average ratio
of bedrock rise to decrease in ice shelf thickness has been running at about
1:10 in recent years.

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jaekwon
I read that as "huge crayon", and for a moment thought all my long held
suspicions had proven true.

~~~
jtms
I read it as both "NSA" instead of "NASA" AND "crayon" instead of "canyon".

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pests
I did too and after all the recent NSA articles I thought it was just par for
the course.

