Lyell Glacier stagnant

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Messages 21 - 40 of total 51 in this topic << First  |  < Previous  |  Show All  |  Next >  |  Last >>
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Feb 5, 2013 - 07:07pm PT
Greg: interesting stuff...thanks for posting this. Are you using GPS to monitor the locations of the stakes? If so, what is the shortest distance change that you can confidently detect from one year to the next? a few inches?
gstock

climber
Yosemite Valley
Topic Author's Reply - Feb 5, 2013 - 07:39pm PT
We did use differential GPS but found that more reliable measurements were attainable with reflecting prisms and a laser rangefinder. The uncertainty on those measurements is about 10 cm over 500 m.
Tobia

Social climber
Denial
Feb 7, 2013 - 01:21pm PT
Greg: when I was teaching I used the NPS video of you measuring the glacier an describing the demise of it a few years back. I wish I could gather those kids around and let them see the now of it.
Jon Beck

Trad climber
Oceanside
Feb 7, 2013 - 01:39pm PT
Interesting but very disturbing stuff. Kinda like watching a train wreck.
Tobia

Social climber
Denial
Feb 7, 2013 - 02:39pm PT
yep, in very slow motion.
Norwegian

Trad climber
Pollock Pines, California
Feb 7, 2013 - 04:25pm PT
dude that sucks,
the glacier aint gettin any action,

total dry spell, i can empathize,

i don't know,
just make the best of scenery for now,

and prop up yourself upon the
hope that big wet cold clouds
bring merry and unprotected
fornication that may well
advance your matrix.

may futures be yours.
here, you can have mine.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Feb 7, 2013 - 05:46pm PT
for more info on the status of glaciers worldwide check out this website...

http://extremeicesurvey.org/

Also, documentary film "Chasing Ice"
http://www.youtube.com/watch?feature=player_embedded&v=eIZTMVNBjc4
Reeotch

Trad climber
4 Corners Area
Feb 7, 2013 - 06:24pm PT
That green stuff is probably olivine. Looks like some nice striations, too.
Sheets

Trad climber
Livermore, CA
Feb 7, 2013 - 08:53pm PT
Bummer,

Kind of mind blowing that the glaciers have shrunk so much in the last 100 years.
Timid TopRope

Social climber
'used to be Paradise, CA
Feb 7, 2013 - 09:28pm PT
Seems like just yesterday I was crawling in the bergshrund (sp) chilling in the blue room...
Does this mean the Lyle glacier gets demoted from glacier status to a mere ice field? I guess the next USGS map update will have to make that call.
QITNL

climber
Feb 7, 2013 - 09:31pm PT
There is some good info here
http://glaciers.research.pdx.edu/glaciers-california
including this comparison photo

Lyell Glacier in 1904 (left, YNP) and in 2003 (right, photo by Hassan Basagic)

Even smaller when I was there, a similar angle:
Credit: QITNL
ionlyski

Trad climber
Kalispell, Montana
Feb 7, 2013 - 10:33pm PT
Am interested in an answer or some discussion on the question Scooter posed upthread. In short, is there a point considered the perfect amount of ice?

Arne
Dingus Milktoast

Gym climber
And every fool knows, a dog needs a home, and...
Feb 8, 2013 - 08:04am PT
I'm curious what you mean - perfect amount of ice for what? Stasis? To make a glacier flow? In the world?

Its either coming or going, innit?

DMT
ionlyski

Trad climber
Kalispell, Montana
Feb 8, 2013 - 10:06am PT
In the world. Or in the USA. Or in Yosemite. Yes, it's coming or going. So, is there a point scientists agree on that is the optimum amount?

Sincere.

As Yosemite Valley was once filled with ice in the ,geologically recent past, what is the point of stasis that the measurement of how much ice should be on Earth vs. should not? Is there a year or epoch that scientist concur on as to when we had the perfect amount of ice?
BBA

climber
OF
Jun 9, 2013 - 11:33am PT
Maybe the optimum amount of ice is enough to prevent a lot of people from starving in various agricultural areas needing water (India comes to mind). It's a sociological question until the population bomb is defused.

The photo which follows is a panorama of Palisade Glacier in August of 1959. How's it doing these days? Any photos?

Credit: BBA
Vitaliy M.

Mountain climber
San Francisco
Jun 9, 2013 - 12:00pm PT
Sill, Polemonium, N. Palisade, and Starlight-our view from camp
Sill, Polemonium, N. Palisade, and Starlight-our view from camp
Credit: Vitaliy M.

October

Palisades
Palisades
Credit: Vitaliy M.

Mid August

Love this place-Palisade traverse in winter &#40;Feb&#41;
Love this place-Palisade traverse in winter (Feb)
Credit: Vitaliy M.

Early February
sempervirens

climber
Jun 9, 2013 - 12:26pm PT
As Yosemite Valley was once filled with ice in the ,geologically recent past, what is the point of stasis that the measurement of how much ice should be on Earth vs. should not? Is there a year or epoch that scientist concur on as to when we had the perfect amount of ice?

That does sound like a climate change denier.

I can't answer but I'll assume those are valid questions. Has glaciology defined a point of stasis? Has there ever been a static amount of ice? It's true that the earth is dynamic, isn't that all the more reason to study what's going on? And a dynamic environment can still be affected by human activities (if that is what you are getting at).

A perfect amount of ice? Perhaps more useful would be, why did the glacier stop moving?, Can we predict other future conditions? what does this tell us about climate? There are many more questions we could ask.
Bruce Kay

Gym climber
BC
Jun 9, 2013 - 01:45pm PT
a glacier will flow once it has sufficient thickness (and slope, which isn't changing here), and conversely will stop flowing when it thins below that threshold



Greg - I assume a pile of ice "flows" similar to an inclined snowpack - faster at tthe surface, slower at the ground interface, so it actually deforms in shape. I'm amazed that no movement at all is detected at the surface if it is inclined at all. Perhaps I'm wrong that it deforms like a snowpack?

The more it think about it, snowpack deforms mostly due to settlement and densification. Ice is already dense and not prone to getting much denser. So a glacier "glides" as opposed to "creeps"?
Doug Tomczik

climber
Bishop
Jun 9, 2013 - 01:55pm PT
Bruce, this source should help to answer your questions.
http://www.antarcticglaciers.org/glacier-flow/
gstock

climber
Yosemite Valley
Topic Author's Reply - Jun 10, 2013 - 11:19am PT
That is a good link, Doug.

Bruce, you are correct that glaciers "creep" through internal deformation of ice. I often explain this as honey flowing down an tilted plate. In this situation the velocity at the honey/plate interface is zero, and increases upward to a maximum velocity at the surface; in essence, the closer you get to the surface, the more motion accumulates from below.

But glaciers, especially temperate ones, also move by basal sliding. In this situation, water at the bed of glacier reduces the basal friction and allows the glacier to slide along the ice/bedrock contact. The analogy here could be the same honey-on-a-tilted-plate scenario, but now the plate is coated with a thin film of oil that allows the whole blob of honey to slide across the plate. In reality the resisting stresses are much higher, so it's very unlikely that a glacier would ever just slip off the mountain!

In most cases total glacier movement is a combination of these two types of movement, with deformation occurring year-round and basal sliding contributing more during the summer melt season.

One of the conundrums of our studies of the Lyell and Maclure glaciers is that the Lyell has a greater surface area but has stagnated, whereas the smaller Maclure continues to move about 25 feet/year. We think that this has to do primarily with thickness - although the Lyell has a larger surface area, it must be very thin to exhibit no movement at all. If correct, this ice will probably melt away very fast in the coming years. I have already seen big changes in ice area in just seven years.

Conversely, the Maclure must still be thick enough to drive some deformation, and numerous crevasses allow meltwater to penetrate to the bed to cause sliding. Last year we placed ice screws into the base of the glacier (accessed by an ice cave at the glacier toe), and when we return this fall we'll measure that movement against the movement of stakes on the top of the glacier. In this way we should be able to parse deformation versus sliding.

Greg

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