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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: October 16, 2018, 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

solartim27

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Re: PIG has calved
« Reply #782 on: October 19, 2018, 12:46:44 AM »
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AbruptSLR

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Re: PIG has calved
« Reply #783 on: October 19, 2018, 06:15:05 PM »
Polarview has a nice shot today,

It appears to me that the SW Tributary Glacier is pushing on the large chunk of the PIIS downstream of the major crevasse shown in your image.  If so, I have little doubt that we will see a major calving event this coming austral summer.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Grygory

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Re: PIG has calved
« Reply #784 on: October 24, 2018, 09:21:38 PM »
Today"s polarview photo (changed colors)
I think it is certain that the glacier will move back 5 km this year.I wonder if only by 5 km or the next rift will grow just as quickly


Stephan

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Re: PIG has calved
« Reply #785 on: October 24, 2018, 10:23:47 PM »
Have all the ice bergs in the open sea disappeared or were they outside of this photograph's frame?

Grygory

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Re: PIG has calved
« Reply #786 on: October 24, 2018, 11:11:22 PM »
Have all the ice bergs in the open sea disappeared or were they outside of this photograph's frame?

They have not disappeared - I wanted to show the rifts  better. It"s the effect of changing colors
original photo:
https://www.polarview.aq/images/105_S1jpgfull/S1A_IW_GRDH_1SSH_20181024T084656_6605_S_1.final.jpg

solartim27

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Re: PIG has calved
« Reply #787 on: October 25, 2018, 04:06:04 AM »
The pinning berg on the Tributary glacier is starting to break up.  All the cracks seem to have progressed fully across PIG.  Still impossible to say when it will go.  Previous large calvings have been preceded by smaller calvings in the left hand notch area, I would expect the same this time.
« Last Edit: October 25, 2018, 08:09:41 AM by solartim27 »
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Wipneus

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Re: PIG has calved
« Reply #788 on: October 25, 2018, 04:55:12 PM »
Three image (60m/pix) animation, showing the developments in the cracking field.

Stephan

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Re: PIG has calved
« Reply #789 on: October 25, 2018, 06:10:56 PM »
Thanks a million for this important animation. I wonder whether this is just another major calving event or whether it is the beginning of the complete collapse of the PIIS.

Reallybigbunny

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Re: PIG has calved
« Reply #790 on: October 25, 2018, 06:30:06 PM »
Wow! Thanks Wipneus. Seems pretty ominous for PIG.

RoxTheGeologist

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Re: PIG has calved
« Reply #791 on: October 25, 2018, 06:48:14 PM »
Seriously: that's amazing. Thanks Wip.

FrostKing70

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Re: PIG has calved
« Reply #792 on: October 25, 2018, 06:51:44 PM »
So this will be the 6th major calving since 2001, and the 3rd in the last 4 years?

FrostKing70

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Re: PIG has calved
« Reply #793 on: October 25, 2018, 06:54:42 PM »
January 2001,
November 2007,
December 2011,
August 2015,
September 2017 (267 square kilometers), and
October 2018  (300 square kilometers)?

oren

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Re: PIG has calved
« Reply #794 on: October 25, 2018, 08:59:23 PM »
Not sure how fast it will break away, but it certainly seems to be hanging by a thread.

Wipneus

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Re: PIG has calved
« Reply #795 on: October 26, 2018, 02:33:31 PM »
Thanks a million for this important animation. I wonder whether this is just another major calving event or whether it is the beginning of the complete collapse of the PIIS.

Estimating the shift in 24 days about 32 pixels (@10m/pix in the original Sentinel images), plus or minus 3 pix gives an average speed of 32*10/24=13.3 m/day (range 12.1-14.6).

I started making such estimates 5 years ago when the speed was about 10, gradually climbing through the years to 11, to 12 and now about 13 m/day.

So speed increases slowly, but not a collapse yet.

On the other hand, if the upstream movement of the calving front is the thing to worry about than I'm not so sure.


AbruptSLR

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Re: PIG has calved
« Reply #796 on: October 26, 2018, 02:46:31 PM »
...
On the other hand, if the upstream movement of the calving front is the thing to worry about than I'm not so sure.

If upstream movement of the calving front abruptly accelerates the ice flow velocity of the SW Tributary Glacier, which in-turn destabilizes the Thwaites Glacier's eastern shear margin, we may all have something to worry about.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Stephan

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Re: PIG has calved
« Reply #797 on: October 26, 2018, 05:24:13 PM »
...
On the other hand, if the upstream movement of the calving front is the thing to worry about than I'm not so sure.

Would it be possible to overlay or animate pictures to show the calving front movement of the last years to have a rough idea whether, and if, how far it has moved inland?
Thanks in advance Stephan

oren

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Re: PIG has calved
« Reply #798 on: October 26, 2018, 05:57:53 PM »
There' s some animations up-thread showing the PIIS behavior over the last few years, here's what I think is the most recent from Feb 2018. Of course it's not updated with the latest advance and cracking.
https://forum.arctic-sea-ice.net/index.php/topic,429.msg142392.html#msg142392

Stephan

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Re: PIG has calved
« Reply #799 on: October 26, 2018, 06:06:18 PM »
Thanks for that link. Eyeballing the calving fronts after big calving events they seem to be at almost identical positions. Wonder whether this holds true for the next big calving event...