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Author Topic: Petermann Gletscher / Petermann Fjord / North West Greenland  (Read 428715 times)

BornFromTheVoid

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #750 on: August 18, 2020, 11:19:57 AM »
Hmm, IDK, Samuel. Is it sea ice thawing or crack opening what we see in your GIF?

In the zoomed in direct comparison i don't see the crack growing really.

I aligned the southern part so as to highlight the gap growth.
Doesn't seem like much, but it's close to 20 m growth on the northern section here
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #751 on: August 18, 2020, 11:48:11 AM »
Right, the gap on that side widened a bit. I agree.

(Great alignment job there, BTW ;) )

Tor Bejnar

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #752 on: August 26, 2020, 06:57:04 PM »
Seasonal evolution of supraglacial lakes on a floating ice tongue, Petermann Glacier, Greenland

by Grant J. Macdonald, Alison F. Banwell and Douglas R. MacAyeal
 Annals of Glaciology, Volume 59, Issue 76pt1  -  July 2018
Quote
Abstract

Supraglacial lakes [SGLs] are known to trigger Antarctic ice-shelf instability and break-up. However, to date, no study has focused on lakes on Greenland's floating termini. Here, we apply lake boundary/area and depth algorithms to Landsat 8 imagery to analyse the inter- and intraseasonal evolution of supraglacial lakes across Petermann Glacier's (81°N) floating tongue from 2014 to 2016, while also comparing these lakes to those on the grounded ice. Lakes start to fill in June and quickly peak in total number, volume and area in late June/early July in response to increases in air temperatures. However, through July and August, total lake number, volume and area all decline, despite sustained high temperatures. These observations may be explained by the transportation of meltwater into the ocean by a river, and by lake drainage events on the floating tongue. Further, as mean lake depth remains relatively constant during this time, we suggest that a large proportion of the lakes that drain, do so completely, likely by rapid hydrofracture. The mean areas of lakes on the tongue are only ~20% of those on the grounded ice and exhibit lower variability in maximum and mean depth, differences likely attributable to the contrasting formation processes of lakes in each environment.
The paper's conclusions end with
Quote
...
Based on previous studies of SGLs on Antarctic ice shelves, the presence of SGLs on Petermann's floating tongue may be indicative of its vulnerability to instability and potential collapse (e.g. Scambos and others, 2000, 2003; Banwell and others, 2013). We find lakes to cover <2.8% of the total surface area of Petermann's tongue, compared with the 5.3% of Larsen B's area that was covered prior to its collapse in 2002 (Banwell and others, 2014). Predicted future rises in air temperature (Kirtman and others, 2013) could enable a higher density of lakes, with larger volumes, to develop from earlier in the season, possibly leading to increased ice tongue instability. However, the decline of SGLs through July and August in each year studied, despite sustained high temperatures during those months, suggests that evacuation of meltwater from the tongue (e.g. by a river cf. Bell and others, 2017) may limit the total volumes of meltwater storage on Petermann's floating tongue, thereby mitigating the risk of instability and break-up.

(I found the article because I was looking for natural "hydrofracking" events being reported.  I had mis-read an ASLR comment a few days ago...)

I know this paper is a couple years old, but I don't recall reading about it before ... 

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #753 on: November 09, 2020, 08:11:05 AM »
Petermann Gletscher:
The crack we have been following for some time now seems to have extended by a few hundred meters from point 2 in the animation and the distance from point 1 to point 2 could now be down to 1.600 meters or 8 % of the width of the glacier.
Notice a new crack branch is developing into the glacier, close to point 2.
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #754 on: November 11, 2020, 10:36:57 AM »
Here is a 8 months study showing the crack expansion at Petermann Gletscher:

Please click on image to enlarge and animate!
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #755 on: November 17, 2020, 08:33:46 PM »
Here is small study to what happened prior to the extremely large calving (+/- 260 km2) that took place on August 10 2010.

Due to difficulties picking up relevant data from Nasa / Landsat I have chosen 3 dates June 30 2010 (about 1,5 month before the calving) July 28 2010 (about 2 weeks before the calving) and August 11 2010 (a day after the calving event).

What really surprised me when I looked into the data, was how close the crack came from starboard to the port side (July 30 2010) before Petermann Gletscher actually calved August 10 2010.

There are many similarities between the situation now and then, the 2020 crack was only 1.600 meters away from the closest crack at port side last time I measured it.
 
But although the 2010 crack was almost perfect (100%), the Glacier chose to take several shortcuts when the glacier actually calved.

I would like to hear your comments to what you see?

Please click on image to enlarge and animate!
« Last Edit: November 18, 2020, 06:03:36 PM by Espen »
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Tor Bejnar

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #756 on: November 18, 2020, 05:35:17 PM »
Thanks, Espen.

Here is some of my thinking:
We often think of ice as being brittle.  Well it is - it cracks!  But it is also elastic.  Even as the middle of the tongue advances slightly faster than the edges (at least, this is typical of a glacier - the ice drags on the side walls), the cracks on the edges shows that forward motion there happens in a jerky motion (little or no motion, then something snaps) and does not only ooze [steady elastic movement], therefore the cracks.  In a perfectly symmetrical glacier, the left (facing 'down stream') side cracks and right side cracks would meet (eventually) in the middle.  In Petermann Glacier, for the currently watched cracks, they will be meeting (we predict) well to the left of center.  The middle (or left of middle, anyway) has more even flow, so the ice continues to ooze there, rather than crack. 

The compression forces in the "1.6 km" wide area (at least) must be strong, as the tongue 'slowly' flows northwestward down the fjord.  Given the tongue is floating, it moves forward by being pushed from behind (where gravity causes the glacier to flow downhill).  Espen's GIF shows the cracks on both sides of the floating tongue are slowly widening at the surface.  Why aren't the cracks closing, given the compression?  I wonder if well-below-the-surface parts of the tongue are still connected.  Might some of the tongues motion be some sort of lateral ridging (buckling), where the crest breaks open, creating a crevasse open at the surface but definitely compressed at the bottom?
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #757 on: November 18, 2020, 09:42:06 PM »
Petermann Gletscher:
Here is an animation containing the period 1976 to 2020.
Included in the animation is the first Landsat documented Petermann calving between 1976 and 1977 and the big 260 km2 August 10 2010 and the latest big calving July 16 2012.

Please click on image to enlarge and animate!
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oren

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #758 on: November 19, 2020, 06:25:06 AM »
I would like to hear your comments to what you see?
I cannot elaborate as much as Tor, but, it seems to me the tributaries on the right play a role in determining the calving position by exerting pressure on the ice shelf, and I also wonder why then and now the last holdout is the middle left of the glacier. I also note the longitudinal channels (on the left) play a small role in the outline of the breakup.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #759 on: November 20, 2020, 11:59:11 AM »
I am surprised with the low numbers of comments, so I will add some more data I find relevant in my shot at what I think is / will be happening next.
As an example I picked the Ryder Gletscher calving on July 20 2016 *), it is a very similar glacier althoug Petermann is bigger but the physics are the same in my opinion:

*) First documented here : https://forum.arctic-sea-ice.net/index.php/topic,886.msg84398.html#msg84398

Click on the image to enlarge and animate!
« Last Edit: November 20, 2020, 12:06:52 PM by Espen »
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SimonF92

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #760 on: November 20, 2020, 01:40:57 PM »
I am surprised with the low numbers of comments, so I will add some more data I find relevant in my shot at what I think is / will be happening next.
As an example I picked the Ryder Gletscher calving on July 20 2016 *), it is a very similar glacier althoug Petermann is bigger but the physics are the same in my opinion:

*) First documented here : https://forum.arctic-sea-ice.net/index.php/topic,886.msg84398.html#msg84398

Click on the image to enlarge and animate!

Espen, I do not feel informed enough to contribute but I always follow these threads and highly enjoy the material you post
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gerontocrat

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #761 on: November 20, 2020, 01:47:05 PM »
I am surprised with the low numbers of comments, so I will add some more data I find relevant in my shot at what I think is / will be happening next.
As an example I picked the Ryder Gletscher calving on July 20 2016 *), it is a very similar glacier althoug Petermann is bigger but the physics are the same in my opinion:

*) First documented here : https://forum.arctic-sea-ice.net/index.php/topic,886.msg84398.html#msg84398

Click on the image to enlarge and animate!

Espen, I do not feel informed enough to contribute but I always follow these threads and highly enjoy the material you post
Same with me...not sure that "Cor, blimey" and "Bloody hell" add much science to the discussion.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #762 on: November 20, 2020, 09:07:59 PM »
Thanks for that important (and very possibly controlling) addition, Oren.
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #763 on: November 21, 2020, 12:03:28 AM »
Hello guys,

I appreciate all your comments, I expected more though from you citizen sciencetist, some of you are heading in the same direction that will be my conclusions, but let's see  if more is willing to contribute to this interesting discussion, you all know Petermann will make headlines again.
And the professionals will not show their cards and and try to make profits from it, a well known exercise in this business, but we can afford to loose in that game!
« Last Edit: November 21, 2020, 12:27:11 AM by Espen »
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oren

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #764 on: November 21, 2020, 12:14:07 AM »
I will add one more observation. After the crack is seen widening significantly, even though it's not yet completed across the glacier, the calving comes along very soon, within days or a few weeks at most. So I am guessing we are nearing the end.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #765 on: November 27, 2020, 12:26:40 PM »
Not really sure if this helps, but the underwater topography might play a role in calving, the bedrock is significantly elevated to the 'left'.

I suspect the calving face is thicker on the left due to the ocean being colder on that side due to less upwelling of warmer currents
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #766 on: March 14, 2021, 05:12:23 PM »
This time it is Petermann Gletscher entering the limelight on the Sentinel 2 stage:

Please click on image to enlarge!
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #767 on: March 28, 2021, 10:32:12 PM »
Petermann Gletscher:
After years of studies, the crack we have watched are now almost complete and only missing about 6 - 7 % of the glacier width.
Resulting in the calving of a +/- 200 km2 calf.

Please click to enlarge and animate!
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #768 on: March 28, 2021, 10:56:01 PM »
When it calves, will the glacier have retreated further than where it was after the previous calving? In other words, will this be a record glacier retreat?

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #769 on: March 29, 2021, 01:22:07 AM »
do we know how thick it is?

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #770 on: March 29, 2021, 08:39:47 AM »
When it calves, will the glacier have retreated further than where it was after the previous calving? In other words, will this be a record glacier retreat?

Nothing spectacular, I will name it status quo compared to 2012, note the black line is the expected next calving line:

Please click on image to enlarge and animate!
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #771 on: March 29, 2021, 09:27:11 AM »
"Nothing spectacular" ? By the time Petermann calves again (July - August ?), it will move further ahead and if it is happening next season the front will be ahead of 2012.
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #772 on: March 29, 2021, 10:14:34 AM »
Thanks for all these updates Espen.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #773 on: March 29, 2021, 10:49:31 AM »
Thanks for all these updates Espen.

Thanks!
The main reason for the calving (my oppinion), is the fact the width in the fjord is sharply reduced from about 19-20 km down to about 16 - 17 km in this area and then there is a bend to the left (port) forcing the glacier to calve. Unless there is a major change in melting and velocity of glacier this area will be where calvings will happen in the future.
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #774 on: April 07, 2021, 11:53:19 AM »
Petermann Gletscher Crack Study:

The crack is still developing, notice the new crack player at port side (Red Arrow)

Over the year the glacier moved +/- 1.100 meter

Please click on image to enlarge and animate!
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oren

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #775 on: April 07, 2021, 12:27:39 PM »
I am amazed that it's still not calved...

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #776 on: April 10, 2021, 09:01:35 PM »
I am amazed that it's still not calved...

I'm not.
As I have been trying to point out, you chaps are looking at the front end of a floating orphaned Ice shelf. The glacier here and in other places like 79 North ends behind the mountains now. The entry channels are plugged with debris. The floating ice has been eroded away from below by subglacial outwash. Parallel shear margin fracturing shows how the whole channel has thinned and ice surface dropped to near sea level. 
Big calving collapses are occurring from the soggy dome every few days at the root of the channel as big cascade ruptures of the basal lake and channel system blast a few more tens of meters off the  base of the ice there.
At Z.I it took less than ten years to fill the 800 m deep basin with rubble under the glacier and chew the ice down to sea level. Same has happened with Humboldt. Now in progress at Petermann.
I don't think there is much to be gained from watching the few thick remnants at the seafront. They are held back by  seafloor terminal moraines at the fronts. Occasionally a basal outburst will shift them if they have thinned enough. But stranded floes at the front of a slush river surely cannot be considered a marine glacial calving front.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #777 on: April 10, 2021, 11:16:40 PM »
This sounds like complete nonsense unrelated to Petermann, but I'll let Espen comment first, I might be misunderstanding something.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #778 on: April 18, 2021, 03:24:42 AM »
Aligning these is near impossible to get close to perfect using Google photos on a phone, however here we seem to have a large piece of the Northern Nares head of Petermann shunt forward towards the Strait.
Between  the 2nd and 17th of April.

Original (reduced to manageable size) images attached also in case anyone can muster the courage to do a better job.
« Last Edit: April 18, 2021, 08:33:15 AM by oren »

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #779 on: April 18, 2021, 06:33:36 AM »
OffTheGrid,
Please stop saying and doing anything
You have misaligned two images relating to two different orbits, moreover one image was in high resolution and the other in low resolution.
You will find below an animation consistent with the images of 24/31, 05/04 and 17/04.
All is quiet and the bears are still sleeping.
Please buy yourself a book, even a very basic one, on geology.
As a bonus, I also post a picture of the rolling mountains.......

PS: I apologise for the fact that the images are not completely aligned, but I can't open the files in Gimps (files are too big for my PC) and I have been reduced to aligning images on the screen.


Click to animate.
« Last Edit: April 18, 2021, 06:42:52 AM by paolo »

OffTheGrid

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #780 on: April 18, 2021, 11:06:04 PM »
Quote
Please buy yourself a book, even a very basic one, on geology.
As a bonus, I also post a picture of the rolling mountains.......
   

That was almost rude enough to be offensive.
If it was not ludicrous enough to give me a fit of giggles.

Do you really think you will find ANY book that has a decent interpretation of the reality of geology?
My father is a genius Oxford trained geologist, with a huge library btw.

By the age of ten I had absorbed his geology books, driven him crazy by questioning everything, and had extensive theoretical understanding of the paradigm believed at the time of his degree, and years of core drilling and analysis experience as his assistant. We lived on a landmass about 200kmx 50km that in an ancient, probably catastrophic deglaciation event had been tipped off a continental shelf, and block inverted with all the strata now upside down. Before being uplifted by the largest submarine Flood Basalt Province recognised on the planet being thrust underneath it.
This and three  estimated 1 km high Tsunami in the last 40kA sweeping over the whole region are common knowledge to our govt scientists now. Clear to us in the 1980s. But in no books or published papers.

Understanding of geology is a fast changing picture from what we observe. But the consensus career goals and politics of academia mire it down.
For example a few months ago was published the seismic interferometry results showing that what is usually referred to as the Iceland hotspot is in fact a small branch from a deep fluid basalt plume that has other branches to Jan Mayen, Svalbard, and a major one to central Greenland. Very likely not the only branches of the system to make surface. Does anyone understand the ramifications of this? Perhaps observing the tiny flood Basalt ongoing in Iceland might help. Recognise that it is hydraulically connected to these other volcanic Islands, through the non-viscous root system. And observe it laying an impermiable sheet across landscapes of porous ash and till.

Thank you however for taking the time to falsify what was seemingly apparent on the comparison of two images I attempted an animation of. Gold medal to you for guts and not resorting to reptile brain kill the threat to worldview without pause to rationalize.

Many of the world's top geologists are emphatic that plate tectonics is a stop start process driven by glaciation/deglaciation events when you talk to them privately. Unfortunate that they commit suicide with their career if they don't keep parroting the circa 1960s uniformitarian line.



Sorry for the OTs Oren. I felt it called for by the amusing suggestion that I should read a basic book on geology.
I would still like to stimulate some discussion on the apparent movements on the East Coast. That area is most threatening to large population groups. Will do it on an appropriate thread. I have a paper somewhere that analyse the collapse of the Antarctic peninsula ice sheet, circa 10000 b.p and shows the timescales, results to the bed over the now open ocean 600km expanse of shelf it cleared. I will try and dredge it out for those who want to understand real geology, not like found in books written to not scare the children.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #781 on: April 18, 2021, 11:25:44 PM »
OTG, I will leave your post as is this time, but will just say this: I don't care how genius you are in geology or any other subject. You must abide by forum rules, including staying on topic, avoiding the promotion of conspiracy theories, and avoiding false claims.
Who judges these things? Unfortunately, myself in this section.
If you still wish to claim north Greenland ia moving large movements, I judge this to be a false claim.
If you still wish to claim that scientists or governments are hiding this, I judge this to be a conspiracy theory.
Feel free to post such stuff elsewhere, but not under my jurisdiction.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #782 on: April 19, 2021, 12:16:18 AM »
Well, if it does not agree with observations, it is wrong. Greenland has not moved 30 kilometers..  ::)

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #783 on: April 19, 2021, 03:22:00 PM »
Whats going on here?
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #784 on: April 19, 2021, 08:18:04 PM »

If you still wish to claim north Greenland ia moving large movements, I judge this to be a false claim.


Am I to understand that Greenland is moving but without any evidence of earthquakes? That would be some trick.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #785 on: April 19, 2021, 08:21:46 PM »

If you still wish to claim north Greenland ia moving large movements, I judge this to be a false claim.


Am I to understand that Greenland is moving but without any evidence of earthquakes? That would be some trick.
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #786 on: April 19, 2021, 11:58:53 PM »
No need to discuss this nonsense, it's already derailed this and other threads.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #787 on: May 06, 2021, 10:59:33 AM »
Petermann Gletscher Crack Study:

A new crack showed up at port side April 27 2021 marked 3. in the animation below.

And the distance between the visible cracks marked 1. and 2. in the animation is now only 1100 meters, or just less than 6 % of the total width of the glacier at this point (+/-19 km).

I am now pretty convinced the calving will happen this year and the calf will be +/- 200 km2

Please on image to enlarge and animate!
« Last Edit: May 06, 2021, 11:05:49 AM by Espen »
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Tor Bejnar

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #788 on: May 12, 2021, 12:55:48 AM »
A new minor crack extension on Petermann Glacial Tongue formed (mostly) around May 2-4.  Images from Sentinel Playground  Image positions adjusted to minimize area movement due to glacial flow.
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nukefix

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #789 on: May 12, 2021, 10:12:54 AM »
Sentinel-1 InSAR would detect an ultra-narrow crack (based on differential movement), and could follow it's evolution ahead of the "visible" crack... it's possible (but not likely) that the calving has alreadt happened on the last scenes.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #790 on: May 24, 2021, 11:17:24 AM »
I'm being more conserviative on predictions these days.
it's this transition zone ice that I'm finding is being the bit that always catches me out.

I'll go as far as saying that sometime within the next 18 months the calving will complete.

NB:
when vewing glaciers I always like to think of them as slow moving fluids, so there is a boundry layer and a transition zone from this to the main glacial flow (which can be either turbulent or laminar)
The transition zones are then made up of highly mixed up ice some of which is old and very hard and some of which is newer and more "fluid" due to the recent churning of the region. Thus due to nature of the glacier in this transition zone, crack propogation is arrested by the ice composition. Somewhat like the hardening processes assoceated with metallergy.

https://en.wikipedia.org/wiki/Hardening_(metallurgy)
https://en.wikipedia.org/wiki/Boundary_layer
https://en.wikipedia.org/wiki/Fracture_mechanics

Yes I know there's lots of papers on ice fracture mechanics and stability but I find that thinking in some simplistic generalisations helps with the basic principles.

Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #791 on: June 18, 2021, 11:19:45 AM »
Petermann Gletscher: Crack study - June 29 2020 - June 17 2021 - Still moving on at the speed of 1.100 - 1.200 meter a year depending on where being measured - Next 4 - 8 weeks will be very interesting to follow.

Please click on image to enlarge and animate!
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Tor Bejnar

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #792 on: June 21, 2021, 06:04:22 PM »
In early June there were a few melt ponds on the Petermann Glacier tongue.  By June 15 there were lots.  Interestingly, it appears some of them drained quite a bit between the 17th and 19th.  Images from Sentinel Playground.

I'm sure water found its way through the ice during the three-day interval.  Did a crevasse extend?  Moulin form (or open up)?  Blockage in drainage channels clear?  Optics change between the 3 days (nothing to see but a mirage)?

(area image: main two ponds (lakes?) of GIF are near the middle)  [Click GIF to enlarge & run, apparently.]

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Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #793 on: June 23, 2021, 10:05:02 AM »
Petermann Gletscher: Crack study - June 29 2020 - June 17 2021 - Still moving on at the speed of 1.100 - 1.200 meter a year depending on where being measured - Next 4 - 8 weeks will be very interesting to follow.

Please click on image to enlarge and animate!

Closing in only to about 500 meters from port side crack to starboard side crack or less than 3 % of the width of the glacier, updates soon.
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Espen

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #794 on: June 23, 2021, 11:41:06 AM »
Petermann Glacier: Another Crack Study - June 17 - June 22 2021 - The red line indicates where the crack is not visible yet.

The red line is about 500 meters
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #795 on: June 28, 2021, 12:14:20 PM »
Before the calving that I believe will take place later this summer.

Lets take a look at the cracks of the 2012 Calf compared to the future Calf, because the 2 calvings will almost be similar except from size the 2010 was 130 km2 and the future calf will be +/- 200 km2, but the cracks before the calvings are almost identical, telling me it is a psycial calving created by the surroundings in other words calvings very similar to what we see at Ryder Gletscher further North. Of course the velocity of the glacier (+/-1.260 meters a year measured June 2021 in the middle of the glacier) and thinning are factors too.

Please click on image to enlarge and animate!
« Last Edit: June 28, 2021, 01:27:09 PM by Espen »
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oren

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #796 on: June 28, 2021, 11:26:57 PM »
It is interesting to note that until 2010 Petermann had contact with a tributary that probably provided some buttressing (upper middle of the image) but that now is far from the front, and that the next calving could possibly remove the last buttressing provided by the next tributary (upper right) which appears to be a strong one.
This effect is on top of the shortening of the ice shelf, which also removes some buttressing by itself.
I wonder if Petermann accelerated slightly after 2010, and if it will accelerate slightly again.

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #797 on: July 01, 2021, 02:18:10 PM »
For the last week or so the Petermann glacier and its catchment area have been subject to strong daily melt.

Presumably this will not do the glacier or the ice in the Nares Strait a lot of good?
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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #798 on: July 15, 2021, 09:22:17 AM »
Petermann Gletscher: Another one of them Crack Studies - The crack is progressing now in a different direction that I expected, but I am still expecting a calving this season.

Please click on image to enlarge and animate!
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Tor Bejnar

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #799 on: July 15, 2021, 03:51:38 PM »
Interesting, Espen!  I see two areas of crack extension (circled).  I actually do not believe my suggested connection between the two.  :o 

The 'upper' crack, I'm certain, drained most of that supraglacial lake.  (I annotated a part of Espen's GIF.)
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"