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FredBear

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Re: PIG has calved
« Reply #750 on: March 06, 2018, 11:03:26 PM »
Apologies to solartim27, there was a new calving. The berg I saw flash out was the stray in the middle on the 3rd, and it moved north (lower) into the rest of the pack by the 4th. Sorry.

solartim27

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Re: PIG has calved
« Reply #751 on: March 10, 2018, 08:04:54 AM »
Nice pic from
https://twitter.com/AntarcticReport/status/972340634739617793?s=20
Where the front of Pine Island Glacier meets the sea; Antarctica’s fastest melting glacier terminates in a short ice shelf, protruding 50km from its grounding line into the Amundsen Sea; the grounding line has retreated inland more than 30km in last 25 years, pic Nicolas Bayou
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solartim27

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Re: PIG has calved
« Reply #752 on: March 20, 2018, 08:01:30 PM »
Excellent Sentinel 2 gif showing the recent small calving, and sea ice forming
https://twitter.com/peter_neff/status/976146007175000065
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solartim27

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Re: PIG has calved
« Reply #753 on: March 23, 2018, 07:11:00 PM »
Excellent thread with lots of info and videos
https://twitter.com/StefLhermitte/status/976945988261859334?s=19
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AbruptSLR

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Re: PIG has calved
« Reply #754 on: March 29, 2018, 05:32:38 PM »
The attached Sentinel 1 image from March 25 2018, makes the ice shelf for the Southwest Tributary glacier look rather fragile to me:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: PIG has calved
« Reply #755 on: April 03, 2018, 05:35:52 PM »
Here is a Sentinel 1 image of the SW Tributary Glacier ice shelf from April 2, 2018; and I believe that it shows a major calving event for this important ice shelf.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

solartim27

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Re: PIG has calved
« Reply #756 on: April 03, 2018, 11:44:45 PM »
New higher res picture shown here:
Not to mention the rift in PIG expanding.  Here's a higher res image from today
https://www.polarview.aq/images/105_S1jpgfull/S1A_IW_GRDH_1SSH_20180403T084646_B9CD_S_1.final.jpg
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solartim27

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Re: PIG has calved
« Reply #757 on: April 04, 2018, 04:47:00 PM »
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oren

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Re: PIG has calved
« Reply #758 on: April 04, 2018, 06:44:02 PM »
Great GIF. I must say the new breakage does seem like a piece of the PIIS itself, and not of the SW Tributary front, which is still holding on somehow.

AbruptSLR

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Re: PIG has calved
« Reply #759 on: April 05, 2018, 03:35:22 AM »
Great GIF. I must say the new breakage does seem like a piece of the PIIS itself, and not of the SW Tributary front, which is still holding on somehow.

While there is room for discussion as to what 'still holding on somehow' does or doesn't mean, the amount of movement exhibited by the old SW Tributary ice shelf front is so large that the buttressing on the glacier itself must be reduced.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Bernard

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Re: PIG has calved
« Reply #760 on: April 05, 2018, 11:03:33 AM »
What strikes me, but I'm no expert, is that this calving event did not deliver a simple big berg, but a lot of fragments. The previous large event has delivered a big berg, but which had split very rapidly in smaller chunks. I interpret both those rapid fragmentations as an indication of internal fragility of the shelf well before the calving. Is this a new behaviour?

oren

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Re: PIG has calved
« Reply #761 on: April 05, 2018, 12:32:19 PM »
What strikes me, but I'm no expert, is that this calving event did not deliver a simple big berg, but a lot of fragments. The previous large event has delivered a big berg, but which had split very rapidly in smaller chunks. I interpret both those rapid fragmentations as an indication of internal fragility of the shelf well before the calving. Is this a new behaviour?
I do think it is a new behavior, and it also seems that the frequency of calving increased, as if smaller chunks are breaking off instead of waiting for the periodical big crack to do its patient work. It feels as if the structural strength of the ice shelf has deteriorated. A few years ago there was the pinned iceberg that remained in front of the advancing glacier for a whole year, moving and rotating but mostly intact. Now they suddenly break at the slightest stimulus.
Note: all of this is subjective gut feeling. It would be interesting if some researcher would compile all calving events, their area, frequency, behavior, and make some statistics.

Bernard

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Re: PIG has calved
« Reply #762 on: April 05, 2018, 02:18:12 PM »
I do think it is a new behavior, and it also seems that the frequency of calving increased, as if smaller chunks are breaking off instead of waiting for the periodical big crack to do its patient work. It feels as if the structural strength of the ice shelf has deteriorated. A few years ago there was the pinned iceberg that remained in front of the advancing glacier for a whole year, moving and rotating but mostly intact. Now they suddenly break at the slightest stimulus.
Note: all of this is subjective gut feeling. It would be interesting if some researcher would compile all calving events, their area, frequency, behavior, and make some statistics.

Indeed. We share gut feelings, at least.  8)

FredBear

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Re: PIG has calved
« Reply #763 on: April 05, 2018, 08:03:30 PM »
PIG used to have a larger ice shelf which had infrequent large calvings which drifted away as slabs (e.g EOSDIS Worldview 14 Jan 2014).
Last summers calving (B44, c.9km long in direction of flow) quickly broke up (and lost its number), but mostly stayed upright.
Recent calvings have been even shorter (c. 1km but remain upright still?), probably compensate for the advance of the glacier.
c.f. Thwaites (to the west) seems to calve relatively short 'bergs - which then seem to collect in "rafts", which tend to hang around in front of the glacier for years - is this the future for PIG?

Grygory

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Re: PIG has calved
« Reply #764 on: April 09, 2018, 08:07:54 PM »

Wipneus

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Re: PIG has calved
« Reply #765 on: June 16, 2018, 07:20:48 PM »
New crack parallel with the existing one developed quite suddenly.

sidd

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Re: PIG has calved
« Reply #766 on: June 16, 2018, 09:43:20 PM »
I posted something about PIG in another thread: Dow et al attribute some fracturing to channelized basal melt:

https://forum.arctic-sea-ice.net/index.php/topic,622.msg159198.html#msg159198

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Wipneus

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Re: PIG has calved
« Reply #767 on: September 21, 2018, 09:11:33 AM »
The sun has returned enabling optical images again. The first cloud-free Landsat image shows clearly two shallow calvings developing in the last few months.

A much deeper crack that was visible on some Sentinel 1 radar images is marked with an arrow in the first image. The second image is a detail with some contrast enhancement.

Grygory

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Re: PIG has calved
« Reply #768 on: September 30, 2018, 06:30:18 PM »
Pine island glacier today in two colors

source: https://www.polarview.aq/antarctic

steve s

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Re: PIG has calved
« Reply #769 on: September 30, 2018, 07:23:22 PM »
Thank you Grygory.

The low angle light shows many cracks extending almost all the way across the glacier. Apart from individual calving events, this seems to indicate a new widespread loss of stiffness for many kilometers upstream, and suggests the imminent loss of buttressing for the SW tributary glacier. 

Grygory

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Re: PIG has calved
« Reply #770 on: October 04, 2018, 02:44:33 PM »
Thank you Grygory.

The low angle light shows many cracks extending almost all the way across the glacier. Apart from individual calving events, this seems to indicate a new widespread loss of stiffness for many kilometers upstream, and suggests the imminent loss of buttressing for the SW tributary glacier.
The surface of the Pine Island glacier is probably not flat like any ice shelf , and it"s only when the contrast increases that you can see the cracks in the lower resolution? -I do not know why even below 99W it looks like the glacier was covered with a whole network of rift -It's the effect of reflections?

https://www.polarview.aq/images/105_S1jpgfull/S1A_IW_GRDH_1SSH_20181001T043553_97BD_S_1.final.jpg


maga

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Re: PIG has calved
« Reply #771 on: October 06, 2018, 08:51:19 PM »
Action! That's a serious one!

Grygory

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Re: PIG has calved
« Reply #772 on: October 07, 2018, 09:03:51 AM »
I have marked approximate lengths in the picture.

Wipneus

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Re: PIG has calved
« Reply #773 on: October 07, 2018, 02:16:51 PM »
Here is the Landsat view, natural colors 30m/pix not entirely cloudless.

Click for the big image (xx MB).

Wipneus

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Re: PIG has calved
« Reply #774 on: October 07, 2018, 03:05:33 PM »
And a Sentinel 1 animation, showing the event took place between 24-30 September.

charles_oil

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Re: PIG has calved
« Reply #775 on: October 07, 2018, 03:27:10 PM »
Great animation - thanks.  What is the potential size of the block that is breaking loose ?

steve s

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Re: PIG has calved
« Reply #776 on: October 07, 2018, 04:39:56 PM »
If I read the animation correctly, the SW tributary glacier is now forcing the cracking and the west side of the PIG is moving faster than the east side near the terminus. That newly enlarged and extended crack shown 5km from the terminus should speed up the tributary glacier's flow -- more so after it calves a berg or bergs.

This summer is likely to be interesting.

Shared Humanity

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Re: PIG has calved
« Reply #777 on: October 07, 2018, 05:47:17 PM »
I think it is more the case that the pinning effect of the Southwest tributary is disappearing as is evidenced by all of the fracturing. The PIG should speed up dramatically as a result and calving will as well. Would not be surprised to see dramatic retreat of the calving face over the next couple of years.

The elimination of the pinning is a state change for this glacier.

solartim27

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Re: PIG has calved
« Reply #778 on: October 07, 2018, 06:20:26 PM »
I wonder if PIG speeds up enough that the calving front could advance instead of retreating.  Here's a screenshot of the trib area, showing one last little bit of pinning.  Original file size is 50 mb.
https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20181007T043512_9850_S_1.final.jpg
« Last Edit: October 07, 2018, 07:01:29 PM by solartim27 »
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Shared Humanity

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Re: PIG has calved
« Reply #779 on: October 07, 2018, 10:09:00 PM »
I wonder if PIG speeds up enough that the calving front could advance instead of retreating.  Here's a screenshot of the trib area, showing one last little bit of pinning.  Original file size is 50 mb.
https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20181007T043512_9850_S_1.final.jpg

Certainly possible. Either way the PIG is going to contribute more to SLR.

Stephan

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Re: PIG has calved
« Reply #780 on: October 13, 2018, 10:10:00 PM »
Wipneus, thanks a million for your contributions in this thread. I discovered this and I am fascinated by the development.
Do you have an actual glacier velocity of the PIG → did it further increase this year?

AbruptSLR

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Re: PIG has calved
« Reply #781 on: Today at 05:13:36 PM »
I wonder if PIG speeds up enough that the calving front could advance instead of retreating.  Here's a screenshot of the trib area, showing one last little bit of pinning.  Original file size is 50 mb.
https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20181007T043512_9850_S_1.final.jpg

Certainly possible. Either way the PIG is going to contribute more to SLR.

Here is an image from Oct 16 2018, which makes it look like the major crevasse is becoming progressively wider.  This suggests to me that we are already witnessing a slow-motion major calving event, that should (in my opinion) result in a major new iceberg sometime this austral summer:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson