Lyell Glacier stagnant

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gstock

climber
Yosemite Valley
Topic Author's Original Post - Feb 5, 2013 - 01:03pm PT
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

Lyell Glacier from Mount Maclure
Lyell Glacier from Mount Maclure
Credit: gstock
klk

Trad climber
cali
Feb 5, 2013 - 01:22pm PT
thanks greg
Reilly

Mountain climber
The Other Monrovia- CA
Feb 5, 2013 - 01:33pm PT
Now it is on par with most SuperTopo participants.
BooDawg

Social climber
Butterfly Town
Feb 5, 2013 - 01:38pm PT
XLNT Greg! Sounds like fun and interesting "work." But someone's gotta do it!

LOL!
scooter

climber
fist clamp
Feb 5, 2013 - 01:54pm 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?
JEleazarian

Trad climber
Fresno CA
Feb 5, 2013 - 02:35pm PT
Now it is on par with most SuperTopo participants.

LOL!

Interesting stuff, as your posts always are, Greg. Thanks.

John
rottingjohnny

Sport climber
mammoth lakes ca
Feb 5, 2013 - 02:41pm PT
Reilly...We started stagnating once the boob thread was deleted...What else is there to look forward to other than watching paint dry...? RJ
splitclimber

climber
Sonoma County
Feb 5, 2013 - 02:45pm PT
aren't they tracking the conness glacier as well? or is it a different research group than the Yosemite group?

QITNL

climber
Feb 5, 2013 - 02:48pm PT
Hey Greg - I saw this article in the paper and realized I might have run into you. Were you and your crew up on Lyell around 9/22 last year? I ran into a team of geologists who were working on such a project. Real interesting stuff. If that were you - nice to meet you.
10b4me

Boulder climber
Somewhere on 395
Feb 5, 2013 - 03:03pm PT
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.
gstock

climber
Yosemite Valley
Topic Author's Reply - Feb 5, 2013 - 03:18pm PT
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
RP3

Big Wall climber
El Portal/Chapel Hill
Feb 5, 2013 - 03:30pm PT
Poor Lyell...

Great work, Greg et al.!
QITNL

climber
Feb 5, 2013 - 03:35pm PT
^Yep, that sounds like you! You were also easy to spot since we were the only ones up there. It was fun watching you guys working. Someone pointed out your markers from previous observations.

I got a couple shots of you guys going about your routine:

Credit: QITNL

Credit: QITNL

Credit: QITNL

A few more here:
http://www.qitnl.com/v/092112/
-Joe
10b4me

Boulder climber
Somewhere on 395
Feb 5, 2013 - 04:41pm PT
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?
QITNL

climber
Feb 5, 2013 - 04:56pm PT
And since I might have a chance to "ask the geologist" - I remember coming across this big weird rock down in the moraine. It looked like a giant tortoise turned on its side, certainly caught my eye:

Credit: QITNL

Credit: QITNL

What the heck would this be?
RP3

Big Wall climber
El Portal/Chapel Hill
Feb 5, 2013 - 05:11pm PT
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.
gstock

climber
Yosemite Valley
Topic Author's Reply - Feb 5, 2013 - 05:25pm PT
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
Gene

climber
Feb 5, 2013 - 05:55pm PT
If it's not moving and is shrinking, is it still a glacier?

Serious question.

Thanks,
g
gstock

climber
Yosemite Valley
Topic Author's Reply - Feb 5, 2013 - 06:07pm PT
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.
QITNL

climber
Feb 5, 2013 - 06:12pm PT
Thanks Greg! - I had a hunch that might be slickenslide stuff but I didn't want to sound stupid. It reminded me of the weird rock at the Beaver St. Wall in San Francisco. Once again, real nice meeting you & I really like the knowledge you share and the work that you do. - Joe

Edit: Here's the story as reported in the SF Chronicle yesterday:
http://www.sfgate.com/default/article/Yosemite-s-Lyell-Glacier-may-be-receding-4250789.php
It also ran on the TV news accompanied with stock footage of Clouds Rest & Half Dome
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