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Author Topic: Pine Island Glacier (PIG) Calving and Discussion  (Read 429271 times)

paolo

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Re: PIG has calved
« Reply #1500 on: January 22, 2020, 09:40:52 PM »
to finish zooming in on the SWT's ice rise

Stephan

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Re: PIG has calved
« Reply #1501 on: January 22, 2020, 10:37:39 PM »
Thank you paolo and blumenkraft for the information. Will check the latest Sentinel pictures tomorrow for the development of further features.
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blumenkraft

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Re: PIG has calved
« Reply #1502 on: January 23, 2020, 11:11:56 AM »
Welcome, Stephan. :)

To make things complete here is the upstream cracks.
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Stephan

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Re: PIG has calved
« Reply #1503 on: January 23, 2020, 07:37:11 PM »
I analysed the latest Sentinel image of the NW tip of the SW Tributary (SWT)
Grounded icebergs (I think we have lost one of them) are circled in yellow.
New and/or widened cracks are marked by red lines
Some minor or mini calvings have happened (green circles)
The zone of destruction S of the tip, adjacent to the much much slower mowing ice W of the SWT is circled in orange. It shows a general widening of the cracks, one of the smaller icebergs within the cracks has tumbled over. I wonder whether a further calving of the tip will open a way for open waters to reach that area. The general flow direction is noted by blue arrows.

See attached picture.
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Stephan

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Re: PIG has calved
« Reply #1504 on: January 23, 2020, 08:03:42 PM »
I analysed the latest development at the E end of the SWT/The Cork area (Dec 27, 2019 vs. Jan 22, 2020).
I didn't detect any microcalving. But some of the cracks have lengthened and widened (marked in red). The triangle in the SW of the Cork has been further squeezed. The new crack in the south of the cork has massively widened (circled in green). I think it will separate soon from the Cork, thereby loosing its contact to the Southern Ice Shelf (SIS).

See attached picture.
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paolo

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Re: PIG has calved
« Reply #1505 on: January 24, 2020, 08:22:46 AM »
The beginning of the end

blumenkraft

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Re: PIG has calved
« Reply #1506 on: January 24, 2020, 08:32:33 AM »
Holy moly. :)
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Stephan

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Re: PIG has calved
« Reply #1507 on: January 24, 2020, 08:43:13 AM »
So, how many meters are left between the new calving front and the western end of R2?
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blumenkraft

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Re: PIG has calved
« Reply #1508 on: January 24, 2020, 09:09:08 AM »
IDK, Stephan. I don't see any joint on the SAR anymore, but of course, you can't really see it due to the low resolution.

Here is a rough overlay with the latest high-resolution picture. Click to play.
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paolo

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Re: PIG has calved
« Reply #1509 on: January 24, 2020, 09:49:27 AM »
my hypothesis

and the joint's still there

paolo

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Re: PIG has calved
« Reply #1510 on: January 24, 2020, 10:00:47 AM »
The high-resolution Sentinel1 image confirms my hypothesis.

blumenkraft

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Re: PIG has calved
« Reply #1511 on: January 24, 2020, 10:02:45 AM »
Cool, haha! That one came in handy!  ;D

Good call, Paolo.

The long wait continues. Any time now...
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paolo

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Re: PIG has calved
« Reply #1512 on: January 24, 2020, 10:12:28 AM »
And mini-calving on the north-west side of SWT

Stephan

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Re: PIG has calved
« Reply #1513 on: January 24, 2020, 04:12:11 PM »
and the joint's still there
thinner and weaker than never before
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blumenkraft

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Re: PIG has calved
« Reply #1515 on: January 24, 2020, 04:59:00 PM »
Yep, tip fell off.
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grixm

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Re: PIG has calved
« Reply #1516 on: January 24, 2020, 05:03:15 PM »
Yep, tip fell off.

We'll have to tow it outside the environment.

blumenkraft

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Re: PIG has calved
« Reply #1517 on: January 24, 2020, 05:37:23 PM »
For sale:

PIG water made from PIG ice.

Taste the water that's thousands of years old.

1l only 13.99 euro.
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paolo

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Re: PIG has calved
« Reply #1518 on: January 24, 2020, 06:50:23 PM »
So the 24/01 two calvings, CR hour by hour (according to the pictures):

Aqua/modis image: no calving

Sentinel1 image: Iceberg: As a result of compression detachment of a splinter from the joint with the Cork (the detached part does not belong to the core of the joint and is next to the part under compression, but now the joint is no longer flanked by lateral thickenings at the compression stress reinforcing it and the joint is so thin ...)

Terra/Modis image: calving of the SW tip of the Iceberg (emblematic of the bad condition of the iceberg, already noticed)

Now he can break at any time.

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« Last Edit: January 24, 2020, 06:57:25 PM by paolo »

baking

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Re: PIG has calved
« Reply #1519 on: January 25, 2020, 05:09:41 PM »
Confirmation from Sentinel-1 that the tip fell off.

RoxTheGeologist

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Re: PIG has calved
« Reply #1520 on: January 25, 2020, 06:10:49 PM »
Confirmation from Sentinel-1 that the tip fell off.

That's just the tip of the iceberg from the upcoming calving.

(Sorry. I'm a Dad.)

blumenkraft

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Re: PIG has calved
« Reply #1521 on: January 25, 2020, 07:46:45 PM »
I can't believe i didn't think of that one...  ;D

Well played, Rox.
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blumenkraft

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Re: PIG has calved
« Reply #1522 on: January 26, 2020, 08:08:39 AM »
Let's see if a little wind can do something...
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Re: PIG has calved
« Reply #1523 on: January 26, 2020, 04:13:23 PM »
Nice and sunny at the PIG today. Pretty Sentinel 2 pics should come in later today. \o/
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paolo

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Re: PIG has calved
« Reply #1524 on: January 26, 2020, 06:30:48 PM »
While waiting for the images of the 26th we have the images of the 25th concerning the ice rumple on the west side of the SWT:
The whole north side is breaking up and calving very quickly, although the icebergs may stay there for a while because of the pinning points:

* Overall picture

* Zooming in on the iceberg that has almost calved

* Animation of the zoom on the south side from the images of 06/01 and 25/01 (the interval is not optimal, different orbits, but the image of 05/01 was not good  >:( )

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baking

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Re: PIG has calved
« Reply #1525 on: January 26, 2020, 07:03:41 PM »
I call this one "Schrodinger's Tip"

Stephan

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Re: PIG has calved
« Reply #1526 on: January 26, 2020, 07:14:04 PM »
Thank you paolo for that latest information. Three days ago I reported about the NW tip of SWT and now there is new calving activity...

Unfortunately I have no access to the Jan 25 or 26 pictures yet.

edit:
If this tipping point gets lost (and only isolated grounded icebergs remain there) and on the other side (along the Cork) the connection to PIIS-MIS is no longer I expect a speeding up and rapid calving of the SWT. The cracks are already there...
« Last Edit: January 26, 2020, 07:26:19 PM by Stephan »
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paolo

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Re: PIG has calved
« Reply #1527 on: January 26, 2020, 07:17:11 PM »
Baking
- «I call this one "Schrodinger's Tip" » ?? I don't understand
- The posted image is a collage of Sentinel Hub from the 25th (for the small floating icebergs) and the 22nd for the future iceberg !!
« Last Edit: January 26, 2020, 07:37:10 PM by paolo »

paolo

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Re: PIG has calved
« Reply #1528 on: January 26, 2020, 07:27:44 PM »
Stephan:
Polar doesn't work well at the moment (at least on my pc), when you click on a date it gives the previous date; to have the image of the 25th you have to position yourself on the ice rumple and ask for the 26th.

paolo

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Re: PIG has calved
« Reply #1529 on: January 26, 2020, 07:33:16 PM »
Baking,
Okay, I understand. :D
For the explanation see the two previous posts: (1527 second point and 1528)

Stephan

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Re: PIG has calved
« Reply #1530 on: January 26, 2020, 07:33:43 PM »
Thank you for this. I have chosen the 26th and finally received the 25th picture.
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Stephan

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Re: PIG has calved
« Reply #1531 on: January 26, 2020, 07:35:04 PM »
I call this one "Schrodinger's Tip"
That is a good one.
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paolo

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Re: PIG has calved
« Reply #1532 on: January 26, 2020, 07:53:46 PM »
For what did not follow, I attach the baking image with notations (the limit between the image of the 22nd and the image of the 25th is just visible, two shades of black)

blumenkraft

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Re: PIG has calved
« Reply #1533 on: January 26, 2020, 08:11:17 PM »
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Stephan

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Re: PIG has calved
« Reply #1534 on: January 26, 2020, 09:03:40 PM »
Two minor calvings of PIIS-MIS visible on the actual EOSDIS picture.
The first one on the NE edge - there are two little new icebergs (circled in green).
The second one along the former tip (circled in green). This calving hasn't been completed yet, but should be visible in more detail tomorrow on Sentinel.
"Schrödinger's tip" has already moved about 26.5 km in W direction (circled in yellow).

The latest minor calvings on the NW edge of SWT (circled in blue) are very hard to see due to the low resolution of EOSDIS. So the actual calvings are bigger than that paolo reported about this afternoon.
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paolo

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Re: PIG has calved
« Reply #1535 on: January 26, 2020, 09:48:44 PM »
Stephan,
The ones you see  at SWT are: the old iceberg, calving in October, which has turned over and quickly grounded and the iceberg in the NW corner, which has hardly moved (grounded) and as the only action it has split in two.
You can see them very well in my first picture of post 1524
« Last Edit: January 26, 2020, 09:55:19 PM by paolo »

paolo

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Re: PIG has calved
« Reply #1536 on: January 26, 2020, 10:09:04 PM »
The image of the 26th is available, but for the reasons mentioned in the previous post, it cannot be accessed (you cannot request a date after the 26th!).
 >:( >:( >:( >:(
We'll have to wait until the date of the 27th is available ...

paolo

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Re: PIG has calved
« Reply #1537 on: January 27, 2020, 01:23:23 AM »
It's the 27th!  ;)
Accessing the images of the 26/01  :)

Attached are the images:
* of the Join Cork-SWT-SIS
* of the joint Cork-Iceberg-MIS
* of the tip of the iceberg

paolo

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Re: PIG has calved
« Reply #1538 on: January 27, 2020, 01:24:47 AM »
Attached:
* R1-R2: Nearly completed joint between R1 and R2 and pause of R2's extension.
* Extension R3

blumenkraft

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Re: PIG has calved
« Reply #1539 on: January 27, 2020, 07:31:47 AM »
Some animations 06. vs. 26.

1&2: The growth of rifts on the north side and a new iceberg
3: The SW joint
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Stephan

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Re: PIG has calved
« Reply #1540 on: January 27, 2020, 06:25:17 PM »
Thank you paolo and blumenkraft for the detailed information.
@blumenkraft: Would you mind to adjust the third gif to the movement of the MIS south of R2? It is a little bit disturbing to find it moving upstream... thanks
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blumenkraft

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Re: PIG has calved
« Reply #1541 on: January 27, 2020, 06:47:15 PM »
Like this, Stephan?
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blumenkraft

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Re: PIG has calved
« Reply #1542 on: January 27, 2020, 06:54:14 PM »
Or this?
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Stephan

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Re: PIG has calved
« Reply #1543 on: January 27, 2020, 06:56:06 PM »
yes - the first one is perfect. Thanks
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blumenkraft

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Re: PIG has calved
« Reply #1544 on: January 27, 2020, 07:04:04 PM »
Welcome! :)

With the very first (third of three) i wasn't sure which spot to chose as a pivoting point because at that zoom level everything is moving into another direction...
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Stephan

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Re: PIG has calved
« Reply #1545 on: January 27, 2020, 08:03:20 PM »
Open waters south of "Cork II" in the zone of destruction (circled in green)
[of course Cork II is not a real cork as it has no solid connection to the Main Ice Shelf (MIS) of PIIS].

See attached picture.
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Jim Hunt

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Re: PIG has calved
« Reply #1546 on: January 27, 2020, 11:09:54 PM »
A new PIG learned journal article, available behind the Nature paywall via Jonathan Bamber's Twitter feed:

https://twitter.com/jlbamber/status/1221878688133865472

Quote
We use high-resolution satellite observations of elevation change since 2010 to show that thinning rates are now highest along the slow-flow margins of the glacier and that the present-day amplitude and pattern of elevation change is inconsistent with fast grounding-line migration and the associated rapid increase in mass loss over the next few decades.
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sidd

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Re: PIG has calved
« Reply #1547 on: January 28, 2020, 07:24:55 AM »
From the Bamber paper referenced by Mr. Hunt:

"we  compare  thinning  rates  derived  from  ICESat-1  for  2003–2009  with  swath-processed CryoSat-2 data from 2010 to 2018."

"Changes in driving stress, due to a steeper slope at the glacier margin, could be responsible for the ice drawdown on the northern flank ...  probably too small  to  explain  the  change "

"Subshelf  melt  rates  increased  from  2013  to  values similar to those from 1998–2010"

"the maximum thinning  rates  during  the  CryoSat-2  epoch,  exceeding  3  m  yr–1  (Figs.  1g  and  2a),  are  occurring  not  in  the  fast-flowing  main  trunk  or  tributaries,  as  previously  reported,  but  beyond  the  shear  margins,  in  areas  of  relatively  slow  flow  (50–100  m  yr–1)  where  motion  is  controlled by ice deformation not basal sliding. By contrast, the fast-flowing main trunk has mean thinning rates of about a factor three lower than the interstream region (Fig. 2a). The peak thinning rate in the interstream region is also associated with an acceleration in flow (Fig. 1c,f) and a modest increase in gravitational driving stress (Fig. 1f ).  Thus,  mass  loss  is  now  propagating  into  areas  of  slow,  deformation-dominated  flow  "

"from 2013, ice shelf thinning recommences with a rate comparable to that in the first decade of the 2000s (Fig. 3). We detect a modest increase in the thinning rate close to the grounding line coincident with  the  resumption  of  oceanic  melting  (Figs.  2, 4c  and  3),  but  in  general,  the  highest  thinning  rates  have  shown  a  decline  between  2012 and 2017"

"therefore, in the  absence  of  anomalously  high  subshelf  ocean  melting,  grounding line retreat and accelerated mass loss of PIG will be limited and at the lower end of model estimates leading to about 3 mm sea level equivalent above the present-day imbalance (of ~0.4 mm yr–1) over the next five decades[6]. We note, however, that subshelf melt rates are sensitive  to  decadal  ocean  variability[27,28]  and  have  a  complex  relationship with climate variability[29,30], the geometry of the cavity[31] and tidal pumping close to the grounding line[32]"

sidd

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Re: PIG has calved
« Reply #1548 on: January 28, 2020, 08:03:01 AM »
"the maximum thinning  rates  ... are  occurring  not  in  the  fast-flowing  main  trunk  or  tributaries,  as  previously  reported,  but  beyond  the  shear  margins,  in  areas  of  relatively  slow  flow

You can see this clearly in the radar pictures. These regions are pitch-black in summer, meaning very wet.
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paolo

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Re: PIG has calved
« Reply #1549 on: January 28, 2020, 07:40:27 PM »
Thank you, Jim Hunt for the reference.

The article is interesting and important, but on first reading it seems to me to be one of those articles that only takes into account part of the aspects with an optimism that I think is excessive and that does not cure my pessimism about the fate of the PIG.  ::)

It requires a reasoned discussion and a harvest of elements which takes time, so it will be for the next few months once the news is over: once Hamlet has chosen: to calve or not to calve?  ;)

Blumenkraft: The areas that we see blackish in the Sentinel images1 are areas of the PIIS (and behind the Hudson Mountains) and the areas referred to in the article: "occurring not in the fast-flowing main trunk or tributaries" are on the contrary upstream of the grounding line, in the PIG (the glacier therefore and not the Ice Shelf). But they are not important, that is not where the fate of the PIG is at stake (at least if there is not a truly catastrophic retreat of the calving front).


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