Pine Island Glacier (PIG) Calving and Discussion

[Stephan]

... We should follow his fate after he has finally calved...

Hmm, could be very hard to do given it's so tiny?

We have watched it so many times, and it has such a unique surface structure. It will be recognizable among the other icebergs. I'll try my best, of course depending on clear Sentinel pictures...

[baking]

This brings me to another point, because I found the nomenclature system we agreed upon (R0, R1, R2, R3, Cork and Cork II) very useful. Therefore I take this calving event as an opportunity to invite the followers of this thread to agree on a further rift numbering system.
I propose to follow the numbers, R3 is still present, and to number the future rifts R4, R5, and so on. This makes communication and explanation of actual events much more easily.

What is your opinion?

Since "R" stands for Rift and R0, R1, and R2 are now the front (or tiny cracks in the front) and R3 will most likely end up the same way I think that terminology is history, but that is my opinion.

[paolo]

Stephan,
Given that I introduced this type of notation I can only agree 

Blumenkraft,
> Cork: it's not good, you find difficulties only because it has bothered you the last two months 
> answer to Oren: and yet in my very first post I had alerted "Total crack" title and image (1204x878) and in the next post I had added the animation just zoomed on the NE side of the... I have the impression that in situations like today the first posts are ignored...

Translated with www.DeepL.com/Translator (free version)

[paolo]

Baking,
You are right, if new rifts appear we can name him R1, R2, ... and, if R3 hasn't calved yet, rename him R3-2019.

Edit: in the same way we will rename R2 in R2-2019 in the very unlikely case that he still hasn't completed the extension to North by finishing his calving.

[baking]

There were a lot of fractures in this calving event and although no one expected this iceberg to stay in one piece for very long due to everything we've been seeing happen lately, I was certainly surprised to see it breakup as it calved and so I've been trying to wrap my head around how it might have happened.

I've added new annotations in yellow to my image below from yesterday.  I think the "before" image works better to help explain what I think happened.

I propose that the calving started at the Northern end where R0 broke through to the marginal ice.  Others have noticed that the calving ice has moved parallel to the front in the Southwestern direction, so I'm assuming that it was pretty forceful.

That force was transferred to the other point of attachment around a bend that resulted in most of the new fractures.  After the second attachment broke free, there were some secondary fractures between R1 and R2 probably caused just by the forceful motion of the ice.

[paolo]

Baking,
I am still convinced that the starting point was the SW side and that is where we had the largest absolute post-calving displacement.
The Iceberg/Cork joint collapsed and all of a sudden this released the tensions that were already there: compression and torsion (the SW side moved much more than the NE side) and this produced the effect we saw and even on the Cork which received a big blow.
But we are a posteriori and it will be difficult to prove it.

Edit: and R1 reached the fracture zone upstream!
Edit2: and the joint Cork/iceberg R2-R3 exploded
Edit3: and the thickening in the middle of the iceberg (white in the image), which could not easily break, was surrounded and isolated by a NE fracture and a SW fracture.

[baking]

I am still convinced that the starting point was the SW side and that is where we had the largest absolute post-calving displacement.

And it somehow pulled this huge iceberg towards the cork?

I'm just going to call you a diehard "corkwatcher" and I mean it in the nicest sense.

[paolo]

The calving force is in reality the release of existing tensions...
Edit3: The iceberg detaches from the Cork, it's free and the tensions are released.

Edit: and how did the movement multiply as it propagated? Movement in the SW is much stronger than in the NE.

Edit2: With the elements that we have in any case many of the answers will remain unknown and/or undemonstrable, but I feel that we here are trying to understand in order to be able to better predict in the future and therefore this discussion is not useless if everyone is able to move forward in this direction.

[Stephan]

I just want to remind all that this calving event has produced the most upstream calving front ever since satellite observation began. 

[Shared Humanity]

Seeing as how the cork received a shattering blow in the process, it would appear that it did have some stabilizing role on the edge of the big iceberg. It's notable how the cork managed to mostly stay in place despite this blow - perhaps it is more attached in its other sides than would appear to be from the sat images.

grounded?

[Shared Humanity]

Thank you guys for following this with such intendity and insight. This has been one of my favourite topics during the past weeks.

Any guesses how the situation will develop? Stabilization to the new calving front or further collapse?

If you look closely a these animations, I think you can see that the large portion of the glacier behind the obviously calved portion has also calved. Will become much more obvious in the next week.

[Shared Humanity]

This brings me to another point, because I found the nomenclature system we agreed upon (R0, R1, R2, R3, Cork and Cork II) very useful. Therefore I take this calving event as an opportunity to invite the followers of this thread to agree on a further rift numbering system.
I propose to follow the numbers, R3 is still present, and to number the future rifts R4, R5, and so on. This makes communication and explanation of actual events much more easily.

What is your opinion?

Give the rift a number that incorporates a date R090220?

[oren]

Stephan,
Given that I introduced this type of notation I can only agree 

Blumenkraft,
> Cork: it's not good, you find difficulties only because it has bothered you the last two months 
> answer to Oren: and yet in my very first post I had alerted "Total crack" title and image (1204x878) and in the next post I had added the animation just zoomed on the NE side of the... I have the impression that in situations like today the first posts are ignored...

Translated with www.DeepL.com/Translator (free version)

Paolo, I saw the total crack, but there was some kind of optical illusion that caused me to see it next to the glacier on the NE side, and along R0 all the way to the SW side. "Blind me" as mentioned. Admittedly, I viewed that on my cell, and the last animation on my PC which probably helped.

[paolo]

Oren,
My apologies, I, like others here, often forget the consultation of the forum on the mobile phone. Indeed we should have made small zoom instead of a single big zoom...

But we have to be fast... 

[Shared Humanity]

I would just like to make the observation that there were, at most, only a handful of people on the planet that were aware of this calving before we were and that says something about you guys.

[paolo]

While waiting for the new images, which should arrive in a few hours, I wanted to add an animation of the calving (images from 08 and 09) with the addition of information about the movements during the calving.
I think it's very meaningful.

twice click to animate and zoom

[KiwiGriff]

Thanks to all the contributors this thread.
Please sirs.
Can we have a gif of both the grounding line, the historic front and the calving to see what we have lost in an easily digested format.

[paolo]

A detail that had escaped me: R1 and R2 did not meet and the joint between the iceberg and the part of the ice shelf between R1 and R2 held what caused the ice shelf between R1 and R2 to burst.

[blumenkraft]

Link this, Griff?

[KiwiGriff]

Almost.
Add.
Grounding line as in when does   ice-cliff instability kick in?
I am looking at the two cracks up stream for the next riveting installments of our long running soap opera.

[paolo]

a detail that has intrigued me since yesterday:
a ridge (longitudinal thickening of the ice shelf) has detached itself from the rest. This is something unusual and I didn't find similar cases in the images of the last calvings.

[blumenkraft]

If you ask me, Griff, these two cracks indicate that the ice behind the supposed grounding line is already starting to float meaning the real grounding line is further south.

If i'm right, ice-cliff instability has already kicked in and the calving front has no say in it.

[KiwiGriff]

I bow before your Superior knowledge Sensei .
That is what I  am suggesting is worth exploring from my ignorance.

[blumenkraft]

Nah, Griff, see it as an educated guess, nothing more. My knowledge is not at all superior. But thanks.

[paolo]

There's no fractures at the grounding line.
Talking about ice-cliff instability is very, very premature.

[blumenkraft]

Paolo, what happens when the grounding line retreats by a lot and parts of the ice mass start floating?

[KiwiGriff]

There's no fractures at the grounding line.

I do not expect a fracture on  the grounding line.
In fact in my humble opinion the grounding line is not the point were ICI kicks in.
As far as my limited understanding goes, Sensei, Ice Cliff Instability  is dependent on height of the calving front not the position of the  of grounding line.
https://www.sciencedirect.com/science/article/pii/S0012821X14007961

Please Sirs .
I just requested an illustration of were we are in comparison of said historic point.
 

[paolo]

Blumenkrafy,
That there is no longer any stress at the base which should lead to an increase in the speed of the glacier if the ice shelf cannot hold it.

To have "ice-cliff instability" the thickness of the ice pack on the calving line must be very high.

Concerning the migration of the grounding line of the PIG, after years of strong retreat in the early 2000s, it has slowed down considerably.

[blumenkraft]

Ice Cliff Instability  is dependent on height of the calving front

This is where i'm coming from. The area we are talking about is indeed elevated.

[KiwiGriff]

From the above linked paper ICI kicks in at about 100 meters .
We seem to be at about 70 + or - 15 .
Still away to go.....yet ,
One could suggest that the calving we have just witnessed will result in accelerated retreat due to a reduction of stress between the PIG and the ice to the west as well as the loss of the ice shelf.

Ideas are free actual evidence rules....keep watching the serial. These are the days of your glacier../.

[paolo]

KiwiGriff,
Attached:
an animation of the PIG between 2003 and 2014

[blumenkraft]

Woah, amazing! <3

[paolo]

Blumenkraft,
As he did mention KiwiGriff."Ice Cliff Instability  is dependent on height of the calving front"

[KiwiGriff]

2020....
I can not easily reconcile your gif with the present reality.
Can we surmise  that the interaction  between pig and ice to the west has changed since 2014 ?

[paolo]

KiwiGriff,
Attached:
an animation of the PIG between 2014 and 2016

[paolo]

KiwiGriff,
Attached:
an animation of the PIG between 2016 and 2019

[blumenkraft]

2000 to 2020 quick and dirty via Nasa-Worldview.

[oren]

Here's another one, courtesy of StefLHermitte. Only goes up to 2018, I tried to edit the gif to slow it down and freeze frame 2018 and even draw the updated front over it but I failed as the individual images were weird and the resolution too low for my capabilities.

[blumenkraft]

Here you go, Oren.

[oren]

Thank you BL, that was quick.

[blumenkraft]

Welcome.

EZGIF is E Z man.

BTW, the RAMMB gave us a few frames could-free catching the event and a calving plume in the north.

[baking]

A detail that had escaped me: R1 and R2 did not meet and the joint between the iceberg and the part of the ice shelf between R1 and R2 held what caused the ice shelf between R1 and R2 to burst.

paolo,
   I don't know what you are trying to say here.  The ice between R1 and R2 broke up in a number of places as you posted on February 4, 5 days before the calving.  What you are now looking at was a long thin piece of ice still connected at the end of R1 but not longer connected to any ice above R2.

What appears to have happened to it is that it moved to the SW and encountered the narrowing between R1 and R2 and and then broke apart.  The energy released from that may have caused the clockwise rotation you have already noted.

Look at the two icebergs shaped like "wood biscuits" (just Google it and look at the images, I can think of no better way to describe them)  And notice that there was no way that ice was going to squeeze past them without something giving way.

Maybe if you weren't so focused on the "cork" you would see the larger picture? 

[paolo]

Baking:
1) I said: "A detail that had escaped me: R1 and R2 did not meet and the joint between the iceberg and the part of the ice shelf between R1 and R2 held what caused the ice shelf between R1 and R2 to burst." This is the description of what happened (see animation). I would have expected the whole piece to detach itself from the iceberg (R1 had almost joined R2). Moreover it's only a detail it's not a piece in the dossier.
2) On the other hand, I am waiting for you to explain to me how a push to one side of the iceberg determining a movement manages to impress a movement three times stronger and in another direction on the other side. (Edit: see post 1665)
3) For me the Cork is only a detail, we can make folklore about it, the important thing is to understand what happened starting from the facts.
Maybe if you weren't so focused on the north side you would see the larger picture?

[baking]

Baking:
1) I said: "A detail that had escaped me: R1 and R2 did not meet and the joint between the iceberg and the part of the ice shelf between R1 and R2 held what caused the ice shelf between R1 and R2 to burst." This is the description of what happened (see animation). I would have expected the whole piece to detach itself from the iceberg (R1 had almost joined R2). Moreover it's only a detail it's not a piece in the dossier.
2) On the other hand, I am waiting for you to explain to me how a push to one side of the iceberg determining a movement manages to impress a movement three times stronger and in another direction on the other side.
3) For me the Cork is only a detail, we can make folklore about it, the important thing is to understand what happened starting from the facts.
Maybe if you weren't so focused on the north side you would see the larger picture?

1) Maybe it is a language issue, but quoting what I quoted to you does not help explain what you meant.  I am as puzzled as ever.  Maybe if you restated it, it might help.  Or if somebody else who understands it could.  I literally have no idea what you are trying to say there.

EDIT: I think I understand now, at least your new text.  The problem is that R1 and R2 had already joined on February 4 so there was no longer any pressure on the end of R1 to join with R2.  The 3 fractures that did happen with the calving were probably caused when the "old pieces" in your picture became wedged between the Eastern edge of R2 and the moving ice still attached at R1.

2) It is like dominoes.  The first crack moves the ice X meters, later cracks also separate and that movement is added to the first movement.  That is why the ice at the Southern end moved further than ice at the Northern end.  Because the cracks started in the North.  I can think of no other explanation for that movement.  If you have one, give it a shot.

[paolo]

It's going fast, so R3 and SWT-SIS are calving...

click twice to zoom out

[paolo]

And the little icebergs of the SWT's ice rumple hang out to join the party

[blumenkraft]

When i looked at the RAMMB shots, i was wondering why the melange in the zone of destruction isn't floating out. Now i know. An iceberg is blocking it, an iceberg that broke off the SWT taking the cork with it.

So, Stephan. Our cork tracking is beginning.

Do i get that right, R4 is now R1?

[paolo]

I don't see anything serious to hold back the little icebergs...

[blumenkraft]

No, it's now open sea basically.

This is why i'm very concerned. R1 (formally R4) and R2 (formally R5) might develop very fast. The next major calving might be pretty soon.

[paolo]

Blumenkraft,
after R3 for the moment there are no serious rifts to be taken into account. we will see in the next few days if the two marginal rifts wake up or not and if central rifts are declared
At the moment he will be named R1 to follow the new calving, but thanks to God for the moment there is nothing.