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gstock
climber
Yosemite Valley
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Topic Author's Original Post - Feb 5, 2013 - 01:03pm PT
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This may be of interest to those of you who frequent the High Sierra. I suspect that this story is playing out on glaciers across the range.
Yosemite National Park's Largest Glacier Stagnant
Lyell Glacier Ceases Movement, Adjacent Maclure Glacier Moving at Historical Rate
The Lyell Glacier, the largest glacier in Yosemite National Park, has stagnated, or ceased its downhill movement, according to a recent study conducted by scientists from the National Park Service and the University of Colorado. The adjacent Maclure Glacier is still moving at its historical rate, about one inch per day.
Glaciers created much of the scenery of Yosemite, including iconic features such as Half Dome. Glaciers are defined as long-lasting ice masses that arise from the accumulation of snow, and move downhill by flowing and sliding. A glacier's health is determined by the amount of winter snowfall compared to summertime melting of snow and ice. The movement of a glacier is primarily determined by the glacier's thickness and steepness. Because they are sensitive to environmental conditions, glaciers are important indicators of climate change.
Building on historical research conducted by John Muir and other notable individuals in Yosemite's history, the research team monitored the Lyell Glacier and the Maclure Glacier, deep in Yosemite's high-country. Movement of the glaciers was monitored by placing stakes in the ice and tracking their positions over a four year period.
Data collected from the stakes placed on the Lyell Glacier showed that no movement has occurred within the last several years. Earlier research on the glacier showed that it was moving in the 1930's. Stagnation has therefore occurred since that time, perhaps within the past decade. In addition, the Lyell Glacier has decreased in size by about 60% since 1900, and has thinned by approximately 120 vertical feet. This thinning of the glacier is most likely why the glacier has stopped moving.
"The Lyell Glacier has historically been recognized as the largest glacier in Yosemite National Park and the second largest in the Sierra Nevada," said Yosemite National Park Geologist Greg Stock, who co-led the investigation with Robert Anderson of the University of Colorado. "However, the lack of movement suggests that the term 'glacier' no longer accurately describes this feature."
The team also measured the Maclure Glacier, which is adjacent to the Lyell Glacier. John Muir first documented movement of this glacier in 1872. The research team mimicked Muir's measurements in 2012 by measuring stakes over the same period of the melt season. Despite a similar amount of ice loss as the Lyell Glacier, the team found that the Maclure Glacier continues to move at the same rate as that measured by Muir, about one inch per day. Although the Maclure Glacier has also thinned substantially, it is still thick enough to move and flow. Much of the downhill movement occurs by slow sliding at the glacier bed due to increased amounts of meltwater.
Research on the glaciers will continue to be conducted through collection of data on snowpack, temperature, and ice melting rates. Guided by records of the local climate archived in the widths of tree rings in nearby forests, the research team will also create a model to show the change in size of the glaciers over the past 300 years. This model will provide insight into the future health of these ice masses.
This work contributes to the growing evidence of ice loss worldwide. The differing behavior of the adjacent Lyell Glacier and Maclure Glacier illustrates the complexity of the landscape's response to climate change. However, the fact that both glaciers are shrinking - causing the Lyell Glacier to cease movement -highlights the impact that a changing climate is having in Yosemite National Park.
Funding for this research project was provided by the Yosemite Conservancy.
Yosemite National Park has a robust research program. The park issues approximately 120 research permits per year, covering a wide array of natural, cultural, and social science subjects. Park scientists collaborate with researchers, mostly from universities and the US Geologic Survey, on the scientific research conducted in the park. Current research topics include studying a tract of old growth forest in the park, the decline of amphibian species in the high-country, and using remote sensing to measure the snowpack.
http://www.nps.gov/yose/parknews/lyellglacier.htm
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klk
Trad climber
cali
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thanks greg
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Reilly
Mountain climber
The Other Monrovia- CA
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Now it is on par with most SuperTopo participants.
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BooDawg
Social climber
Butterfly Town
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XLNT Greg! Sounds like fun and interesting "work." But someone's gotta do it!
LOL!
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scooter
climber
fist clamp
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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?
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JEleazarian
Trad climber
Fresno CA
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Now it is on par with most SuperTopo participants.
LOL!
Interesting stuff, as your posts always are, Greg. Thanks.
John
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rottingjohnny
Sport climber
mammoth lakes ca
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Reilly...We started stagnating once the boob thread was deleted...What else is there to look forward to other than watching paint dry...? RJ
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splitclimber
climber
Sonoma County
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aren't they tracking the conness glacier as well? or is it a different research group than the Yosemite group?
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10b4me
Boulder climber
Somewhere on 395
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thanks for the info.
just curious, if there is the same out of loss on both the Lyell, and Maclure glaciers, why is the Maclure still moving? is it because of the melt water? wouldn't melt water allow the Lyell to move also? very interesting.
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gstock
climber
Yosemite Valley
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Topic Author's Reply - Feb 5, 2013 - 03:18pm PT
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That's a good question, and one we don't have a simple answer for. I strongly suspect it comes down to thickness; 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 - perhaps 150 feet thick or so. Lyell appears to be thinner than that, while the Maclure is probably thicker. Because it is still moving, the Maclure Glacier has many crevasses which allow meltwater to get to the bed and enhance sliding, so there is a positive feedback there, at least for now. The Lyell Glacier no longer has crevasses.
A group from UC Berkeley was monitoring stakes on the Conness Glacier, but I believe they had problems with the stakes melting out during the summer. We hauled in a steam drill to sink our stakes about 15 feet into the ice but still they nearly melted out after a few years.
QITNL, I was up there at that time so we probably did meet. With ice augers, PVC poles, and GPS antennae sticking out of our packs, we tend to attract a lot of attention on the trail.
Greg
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RP3
Big Wall climber
El Portal/Chapel Hill
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Poor Lyell...
Great work, Greg et al.!
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10b4me
Boulder climber
Somewhere on 395
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Greg, thanks for your answer.
I climbed Lyell in 1980. seems like we stepped off the glacier onto the summit.
How thick is the Conness glacier?
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RP3
Big Wall climber
El Portal/Chapel Hill
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From a distance, it looks the granodiorite of the Kuna Crest (makes sense given where you found it.
The "tortoise-shell" surfaces are a bit confusing to me. My hunch is joint surfaces. I find it hard to believe that they are glacial polish given that it is present on both sides.
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gstock
climber
Yosemite Valley
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Topic Author's Reply - Feb 5, 2013 - 05:25pm PT
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QITNL, great photos, thanks. I think the tortoise shell-looking stuff is caused by minerals (maybe epidote?) that precipitated along a fracture surface (a small fault in this case). The striations are called "slickensides" and formed as one block slid past another.
10b4me, I'm not sure how thick the Conness Glacier is, and I don't know whether it is presently moving or not.
Greg
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Gene
climber
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If it's not moving and is shrinking, is it still a glacier?
Serious question.
Thanks,
g
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gstock
climber
Yosemite Valley
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Topic Author's Reply - Feb 5, 2013 - 06:07pm PT
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A glacier can be shrinking and still move downhill. However, movement is a defining feature of a glacier, so once it stops moving then it is arguably not a glacier anymore.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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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?
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gstock
climber
Yosemite Valley
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Topic Author's Reply - Feb 5, 2013 - 07:39pm PT
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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.
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Tobia
Social climber
Denial
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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.
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Jon Beck
Trad climber
Oceanside
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Interesting but very disturbing stuff. Kinda like watching a train wreck.
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Tobia
Social climber
Denial
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yep, in very slow motion.
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Norwegian
Trad climber
Pollock Pines, California
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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.
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Reeotch
Trad climber
4 Corners Area
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That green stuff is probably olivine. Looks like some nice striations, too.
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Sheets
Trad climber
Livermore, CA
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Bummer,
Kind of mind blowing that the glaciers have shrunk so much in the last 100 years.
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ionlyski
Trad climber
Kalispell, Montana
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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
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ionlyski
Trad climber
Kalispell, Montana
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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?
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BBA
climber
OF
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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?
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Vitaliy M.
Mountain climber
San Francisco
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October
Mid August
Early February
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sempervirens
climber
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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.
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gstock
climber
Yosemite Valley
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Topic Author's Reply - Jun 10, 2013 - 11:19am PT
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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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Patrick Sawyer
climber
Originally California now Ireland
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So, as asked above, is Lyell still a glacier or just an ice field? Or has it yet to be determined which? I was only on Lyell once in the mid-1970s.
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donini
Trad climber
Ouray, Colorado
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Y'all call that a glacier......Patagonia is having a wet, cold winter and there are big smiles on the glaciers. There is nothing sadder than a dying glacier.
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Chiloe
Trad climber
Lee, NH
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Jim, do you have any personal observations from your years around Patagonian glaciers? I haven't been there but I've seen reports like this,
Patagonian Glaciers Melting in a Hurry
Ice fields in southern South America are rapidly losing volume and in most cases thinning at even the highest elevations, contributing to sea-level rise at "substantially higher" rates than observed from the 1970s through the 1990s, according to a study published Wednesday.
http://www.scientificamerican.com/article.cfm?id=patagonian-glaciers-melting-in-a-hurry
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donini
Trad climber
Ouray, Colorado
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The Patagonia Ice Caps, North and South are the two largest ice caps outside of the polar regions.....1,500 and 5,500 sq. mi. respectively. The last few summers have been hotter and dryer than normal. This winter they are getting a reprieve....quite wet and cold.
I have noticed recession but the glaciers are so large it's hard to determine how much.
When I was on Mt. Kenya in 2005 I compared what I saw with earlier pictures and the rate of recession was astonishing.
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SCseagoat
Trad climber
Santa Cruz
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A phenomenal documentary if you haven't seen it already
ABOUT THE FILM Chasing Ice is the story of one man’s mission to change the tide of history by gathering undeniable evidence of climate change. Using time-lapse cameras, his videos compress years into seconds and capture ancient mountains of ice in motion as they disappear at a breathtaking rate. - See more at: http://www.chasingice.com/#sthash.sCHg1E2n.dpuf
http://www.chasingice.com/
Susan
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