Support the Arctic Sea Ice Forum and Blog

Author Topic: PIG has calved  (Read 321026 times)

Stephan

  • Grease ice
  • Posts: 758
    • View Profile
  • Liked: 230
  • Likes Given: 126
Re: PIG has calved
« Reply #1100 on: November 05, 2019, 06:50:51 PM »
Micro calving at PIIS today.
Close to the "cork" the part NE of it which showed enhanced cracks in blumenkraft's animation has gone (circled in orange). The iceberg has moved fast into NW direction which shows the strength of the current in Pine Island Bay.

See attached picture. Sorry for the unclear view due to high clouds.


PS: A daily observation opf PIIS/PIG seems to be necessary!
It is too late just to be concerned about Climate Change

crandles

  • Young ice
  • Posts: 2511
    • View Profile
  • Liked: 94
  • Likes Given: 47
Re: PIG has calved
« Reply #1101 on: November 05, 2019, 06:56:28 PM »
Micro calving at PIIS today.
Close to the "cork" the part NE of it which showed enhanced cracks in blumenkraft's animation has gone (circled in orange). The iceberg has moved fast into NW direction which shows the strength of the current in Pine Island Bay.

See attached picture. Sorry for the unclear view due to high clouds.


PS: A daily observation opf PIIS/PIG seems to be necessary!

I was wondering whether to try to name that the 'cork clip', but now it has gone without the cork following (at least not just yet), I guess it is too late.

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1102 on: November 05, 2019, 09:42:41 PM »
Attached:

1) Today's Polar View image of calving (04h UTC)
    No calving in yesterday's image (04h UTC) and therefore 9 km in less than 24 hours

2) The Sentinel image of 10/24

3)The Sentinel image of 11/03 with comments on calving and differences with the previous image

Click to expand images

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1103 on: November 05, 2019, 09:45:41 PM »
Question:

Why to expand my images to the maximum you have to click twice?

blumenkraft

  • Nilas ice
  • Posts: 1271
  • Fans of Hans Club - circa 2018
    • View Profile
  • Liked: 580
  • Likes Given: 820
Re: PIG has calved
« Reply #1104 on: November 05, 2019, 09:50:00 PM »
I only have to click once. Might be a Mac/PC difference?
Refugees welcome

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1105 on: November 05, 2019, 10:16:59 PM »
I have to click twice, the first time I open another window with an enlarged image, but not to the maximum

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1106 on: November 05, 2019, 11:16:42 PM »
Question:

Why to expand my images to the maximum you have to click twice?
Could be an image size issue.  Images up to size A re displayed full size on the page.  Above that size they are opened in a window of size B.  If they are larger than B they require another click to see at maximum resolution.

Edit:  I think A is 700 pixels and B is 1400 pixels.

Edit: Edit: B might be 1000 pixels.
« Last Edit: November 05, 2019, 11:25:39 PM by baking »

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1107 on: November 05, 2019, 11:21:39 PM »
Thank you very much

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1108 on: November 06, 2019, 04:31:13 PM »
Today's Polar view image (06/11/2019 8H UTC) is much more detailed and I'll correct my comments on the Sentinel image of 03/11/2019 (post 1102)

Note: the iceberg is later moved to the W, the outbound current is strong and the warm underwater current must be as strong….

Attached:
1.   The Polar View image of 06/11/19
2.   Zooming in on the calving's location
3.   The Sentinel image with corrected comments

Wipneus

  • Citizen scientist
  • Young ice
  • Posts: 3996
    • View Profile
    • Arctische Pinguin
  • Liked: 619
  • Likes Given: 0
Re: PIG has calved
« Reply #1109 on: November 06, 2019, 08:18:59 PM »
The cracks are so wide now that we can see an iceberg breaking off and toppling over, withing the crack. If I am not mistaken of course.

blumenkraft

  • Nilas ice
  • Posts: 1271
  • Fans of Hans Club - circa 2018
    • View Profile
  • Liked: 580
  • Likes Given: 820
Re: PIG has calved
« Reply #1110 on: November 06, 2019, 08:30:37 PM »
hmmm, this might be bad news.

This is a GIF showing some frames of last summer and two frames this summer. Note the upper right crack. This is, according to the Sentinel map, directly above the rounding line.

Location is eastern side, like 40/50km upstream.

Click to play
Refugees welcome

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1111 on: November 06, 2019, 09:14:02 PM »
Wipneus, it seems to me that it breaks into three pieces:

1.   the point (top of the image), which it rotates partially (you can always see the superficial part, even tilting)

2.   a piece (right) that doesn't turn

3.   the remaining part that rotates completely or almost

Note: At the top you can see the iceberg partially returned already reported (post 1067)
« Last Edit: November 06, 2019, 09:22:06 PM by paolo »

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1112 on: November 06, 2019, 09:32:36 PM »
The cracks are so wide now that we can see an iceberg breaking off and toppling over, withing the crack. If I am not mistaken of course.
You are correct.  Small (non-tabular) icebergs do this frequently.  The underside of the ice does not back-scatter like the snow covered upper surface so it appears darker with some highlights to the radar.

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1113 on: November 06, 2019, 10:16:38 PM »
Location is eastern side, like 40/50km upstream.

Northern side?  15-20km upstream from the ice front?  It's ice rise rise above the northern ice shelf.  See the red arrow in the map below, if it is where I think it is.

Stephan

  • Grease ice
  • Posts: 758
    • View Profile
  • Liked: 230
  • Likes Given: 126
Re: PIG has calved
« Reply #1114 on: November 06, 2019, 10:45:50 PM »
The place your arrow points at is roughly where the NE end of the actual calving front is, close to Evan's Knob.
The new crack blumenkraft detected (thanks !) is much further upstream, indicated by the tip of the black arrow. Sentinel says this is where the grounding line used to be around 2010.

See attached picture.
It is too late just to be concerned about Climate Change

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1115 on: November 07, 2019, 02:43:30 AM »
The place your arrow points at is roughly where the NE end of the actual calving front is, close to Evan's Knob.
The new crack blumenkraft detected (thanks !) is much further upstream, indicated by the tip of the black arrow. Sentinel says this is where the grounding line used to be around 2010.

See attached picture.

Oops!  Good catch.  Here is a revised map.

blumenkraft

  • Nilas ice
  • Posts: 1271
  • Fans of Hans Club - circa 2018
    • View Profile
  • Liked: 580
  • Likes Given: 820
Re: PIG has calved
« Reply #1116 on: November 07, 2019, 09:28:27 AM »
That's the correct location, Stephan! Thanks for pointing it out.

Sorry for not being detailed enough, Baking.

Here is a GIF showing the supposed Sentinel grounding line.


https://m.imgur.com/ha91dZW
Refugees welcome

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1117 on: November 07, 2019, 01:32:13 PM »
I pulled all the high resolution Sentinel-1 images I could get.  I have a bunch from late March through late June then there is a four month gap and a new set in the last 30 days with the most recent being from today.  I made them into a GIF below and I have labeled today's image with the significant features.

I think the most significant observation is the new rifts forming on the glacier side of the shear margin.  Presumably they are forming after the glacier passes the submerged ridge.  Two have formed in the last year or so.  These are important because they are moving with the glacier and if they continue to form and move along they will weaken more and more of the northern shear margin causing continued acceleration of the glacier.  (This is what happened on the southern shear margin beginning in 1999 and the rifts there have almost reached the ice front.)

What I am call thing the Northern Ice Shelf "Pocket" is a roughly triangular shaped shelf that is not attached to the rest of the Northern Ice Shelf.  It is bordered by the Pine Island glacier to the South, the Hudson Mountains to the North, and a submerged ridge to the East.

The new crevasse (I hesitate to call it a "crack") is probably a transverse crevasse caused by movement of the ice shelf off of the ridge.  Whether this movement is faster than normal is hard to say.  The important point is that the crevasse is relatively stationary and not moving with the glacier.  Yes the shelf does provide support for the glacier, and weakening of the shelf does imply further weakening of the glacier, but I find the spreading of the rifts along the margin to be a greater concern.


charles_oil

  • Frazil ice
  • Posts: 302
    • View Profile
  • Liked: 22
  • Likes Given: 35
Re: PIG has calved
« Reply #1118 on: November 07, 2019, 02:21:44 PM »
Many thanks Baking for the gifs!    Any chance it could pause / stop at the latest with a click to restart - its hard to see when its rolling round and round (and I dont know how to put it on slow-motion).

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1119 on: November 08, 2019, 01:49:41 AM »
Many thanks Baking for the gifs!    Any chance it could pause / stop at the latest with a click to restart - its hard to see when its rolling round and round (and I dont know how to put it on slow-motion).

Don't know how to make a GIF that stops, but here is one that pauses before a 3-month gap and at the end.  Also a slower frame-rate.  Hope it helps.  There are also tools to split a GIF into individual frames, some are web based.

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1120 on: November 08, 2019, 02:16:56 AM »
So, I just happened to notice this happening on the opposite "bank" of PIG.

It's on the Southern Shear Margin, at the Eastern end of the Southern Ice Shelf.  There's a gap in the GIF between June 22 and October 8 which is when this "event" happened.

oren

  • Young ice
  • Posts: 4465
    • View Profile
  • Liked: 866
  • Likes Given: 1285
Re: PIG has calved
« Reply #1121 on: November 08, 2019, 08:09:22 AM »
Seriously excellent stuff, baking. Thank you.
Note the slower gifs are much clearer.

blumenkraft

  • Nilas ice
  • Posts: 1271
  • Fans of Hans Club - circa 2018
    • View Profile
  • Liked: 580
  • Likes Given: 820
Re: PIG has calved
« Reply #1122 on: November 08, 2019, 05:52:50 PM »
Yes, plus one! Thanks for those GIFs, Baking. :)
Refugees welcome

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1123 on: November 08, 2019, 07:27:56 PM »
I've slowed down the GIF and paused it at three images.  I've also labeled areas on each of the images for the following reconstruction of the narrative.  As always, the dates of the images are in the file names and all images are from Sentinel-1 radar images via Polar View.

March 24:  This is the earliest image I have available for now.  The site is a point on the Southern Shear Margin of Pine Island Glacier where it passes a submerged ridge and then expands causing rifting along the margin, separating the glacier from the rest of the ice shelf.  A small strip of older ice appears to have partially pulled away from the submerged ridge while possibly still connected to some ice between a couple of older rifts.

June 22:  The "break-away" strip has been caught in the flow of the shear margin and appears to have caused the opening of the old rift.  This open has weakened a large section of older upstream ice causing a rapid collapse next to the ridge.

November 7:  The collapsed ice has backed-up behind the rift, causing the rift to open even wider which has put stress on old ice downstream from the rift.

The end result of this will ultimately be the weakening of the Southern Ice Shelf which forms the Southern Shear Margin of PIG removing even more downstream resistance to the accelerating glacier.

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1124 on: November 08, 2019, 09:55:53 PM »
I wanted to do a movement analysis in the current joint between PIG and SWT.

The results clearly show the play of the pressures between PIG, SWT and the three pieces of the SSI forming the join between PIG and SWT, which lead these three pieces to strong deformations, and, in the case of piece 3 ("Cork"), to calving’s and to turn (which caused an acceleration in the movement of the corresponding part of the PIG that generated the recent mini-calving

Attached to this post:

1.   The image of 03/11/2010 with general notations for existing elements (in red), join limits (orange), main actions: deformations, compressions, rotations and update with the mini-calving of 06/11

2.   Always the image of 03/11 with indications of movements between 24/10 and 03/11 (10 days). For each position tested I circled with a circle the area containing the points tested (for each position I measured the displacement of several points to check the consistency of the measurements; normally 2 or 3). I also measured changes in the distance between two points straddling the PIG rift

3.   The image of 31/01/2019 with the notations relating to the current join (this image clearly shows the deformations that have occurred since 31/01)
« Last Edit: November 08, 2019, 10:02:13 PM by paolo »

Stephan

  • Grease ice
  • Posts: 758
    • View Profile
  • Liked: 230
  • Likes Given: 126
Re: PIG has calved
« Reply #1125 on: November 08, 2019, 10:48:08 PM »
Excellent job, paolo, Thanks a million.
The look at the "cork" ten months ago shows how broad it had been at that time.
I also saw the very little piece (numbered "2") being further compressed in blumenkraft's last animation from Nov 4.
It is too late just to be concerned about Climate Change

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1126 on: November 09, 2019, 09:11:34 PM »
In future posts I would like, before to consider future changes, to analyze the current situation
of the SWT and the part of the SIS between PIG and SWT, and more specifically that being in contact with the current join PIG-SWT.

But first, I would like to document the recent history of the join PIG-SWT and its switching from a strong and direct join PIG-SWT to an indirect link (with components of the SIS between the two), less strong, uncertain and much further back

Attached:
1.   A mov file relating to the PIG from 1975 to 2011(Rignot et al. 2014)
2.   A mov file relating to the PIG from 2001 to 2018(Alley et al. 2019)
3.   A composite image with the PIG-SWT join of 12/01/17, 18/01/18, 28/12/18 and 06/11/2019
« Last Edit: November 09, 2019, 10:58:59 PM by paolo »

blumenkraft

  • Nilas ice
  • Posts: 1271
  • Fans of Hans Club - circa 2018
    • View Profile
  • Liked: 580
  • Likes Given: 820
Re: PIG has calved
« Reply #1127 on: November 13, 2019, 04:43:39 PM »
TIL there is a gyre in front of the calving front!

23 frames, 51-minute increments ( there is a gap though, you'll notice )
Refugees welcome

Stephan

  • Grease ice
  • Posts: 758
    • View Profile
  • Liked: 230
  • Likes Given: 126
Re: PIG has calved
« Reply #1128 on: November 13, 2019, 10:34:10 PM »
Where is this gyre located exactly?
It is too late just to be concerned about Climate Change

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1129 on: November 14, 2019, 03:33:44 AM »
Where is this gyre located exactly?
75S/102W

paolo

  • New ice
  • Posts: 26
    • View Profile
  • Liked: 16
  • Likes Given: 0
Re: PIG has calved
« Reply #1130 on: November 14, 2019, 03:11:57 PM »
blumenkraft,

Attached is a figure from Thurnherr et al. (2014) related to gyre.

Notice of this figure :

Figure 1.Observations in Pine Island Bay (inset), including topography (gray-shaded contours; Nitsche et al. [2007]), Pine Island Glacier calving front (red line), near-surface velocity field (green arrows), radial gyre transport above 700m (red labels), and potential density anomaly between 500 and 550 m (colored bullets). Arrows show SADCP velocities averaged between 30 and 300m and gridded into ~3x3 km horizontal boxes. The large blue circle indicates the approximate extent of the gyre dominating the upper-ocean circulation in PIB, with the blue star marking its center. Numbered CTD station bullets are discussed in the text; ‘‘R’’ labels indicate repeat station

Note: the mini iceberg calved the 05/11 goes around in circles in the gyre (see image of previous baking post)

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1131 on: November 14, 2019, 04:48:50 PM »
I'm finding numerous sources that say the CDW flows up the northern margin of PIG and returns down the southern margin, which would be consistent with the clockwise gyre at the ice front.  And  there are apparently two gyres under the ice now, on either side of a transverse ridge.

blumenkraft

  • Nilas ice
  • Posts: 1271
  • Fans of Hans Club - circa 2018
    • View Profile
  • Liked: 580
  • Likes Given: 820
Re: PIG has calved
« Reply #1132 on: November 14, 2019, 06:54:54 PM »
@paolo, awesome, thanks a lot.

@baking i'm guessing caused by tidal forces?
Refugees welcome

baking

  • New ice
  • Posts: 56
    • View Profile
  • Liked: 54
  • Likes Given: 1
Re: PIG has calved
« Reply #1133 on: November 14, 2019, 08:51:20 PM »
@baking i'm guessing caused by tidal forces?

I don't think CDW is effected much by tides.  It is probably more the underwater terrain in combination with water temperatures.  Colder water temps block the CDW from entering over a 700 meter deep ridge, causing the CCW rotation in figure 4e below.  Warmer temps allow the CDW through causing the CW circulation in figure 4f.

See Webber 2017 "Mechanisms driving variability in the ocean forcing of Pine Island Glacier"
https://www.nature.com/articles/ncomms14507