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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #350 on: July 31, 2015, 06:29:46 PM »
I expect the new splitting tension crack that A-team discusses will likely result in another major calving event within two years or less, and a repetition of this mechanism will progressive move the PIIS calving face upstream, thus progressively relieving buttressing from the SW Tributary Glacier which will progressive induce the adjoining Thwaites Glacier ice flow velocities to accelerate.

It seems to me the 2013 calving happened at the point where the northern end of that crack reached almost exactly the same point as the northern end of the latest crack has just reached.

See
http://www.bbc.co.uk/news/science-environment-23249909
(linked in first post of this thread)

Is the buttressing from the rock at the northern side the critical point, and wouldn't that continue for a while possibly with thinner glacier possibly moving faster and calving more frequently but at the same point?

(Note I probably don't know what I am talking about and could easily be misjudging the position to be about the same.)

From a fracture mechanics point of view the pre-existing crevasses and basal meltwater channel patterns are critical (together with other boundary conditions, ice thickness and shelf location & geometry) for determining whether the failure mechanism will hinge about the north or south end of the splitting tension crack.  I suspect that the 2013 calving event swung out at the north end because local cracking around the submerged pinnacle allowed it to swing free there; while I suspect that this 2015 event has the calving face located further upstream than the 2013 event, so that the lateral (downstream) kicking force was stronger, and as Yuha points out there were likely sufficient pre-existing basal grooves (or channels) cut in the bottom of the ice shelf to allow a wedge shaped iceberg to be kicked out (also pushing the southern iceberg ahead of it).

As the calving face moves still further upstream, we may see different variations of calving events that are slightly different than both the 2013 & 2015 event but also with many commonalities.

Certainly, the PIIS is becoming thinner, and with the El Nino should have more subglacial meltwater grooves (channels); so for some decades to come we can certainly expect major calving events to me more frequent.
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oren

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #351 on: August 01, 2015, 01:47:49 AM »
Thanks to all those that responded to my rather stupid question. It all clicked into place.

sidd

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #352 on: August 01, 2015, 05:14:26 AM »
the name of this thread ought to have " again" at the end. I am sure people will be discussing this for a few more years (until the discussion moves to "Thwaites has fallen in, run inland and upwards")

sidd

oren

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #353 on: August 01, 2015, 09:34:23 AM »
Is it possible to compare the calving front position to the position after the previous major calving? I'm wondering if there's a retreat or not.

solartim27

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #354 on: August 02, 2015, 05:10:28 PM »
Just a glimpse of the notch area today.  Rotation around the pinnacle is evident.
FNORD

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #355 on: August 03, 2015, 01:46:28 AM »
Just a glimpse of the notch area today.  Rotation around the pinnacle is evident.

solartim27,

Another nice catch.  This image shows that the western face of the pinned iceberg clearly follows the alignment of the old splitting tension crack.  It will be interesting to see how long it takes for this iceberg to un-pin itself.

Best,
ASLR
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Wipneus

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #356 on: August 03, 2015, 02:23:28 PM »

Do you have earlier frames handy? To date the new crack, see when it developed, whether it is progressing. Also one longitudinal crack, bottom left, seems to pre-date the horizontal developments.


Sorry I missed this question at first. These are the PIG files that I have:

S1A_IW_GRDH_1SSH_20141009T084630_20141009T084655_002750_003169_F84D.zip
S1A_IW_GRDH_1SSH_20141010T043522_20141010T043546_002762_0031AF_F034.zip
S1A_IW_GRDH_1SSH_20141022T043522_20141022T043547_002937_00355B_95D6.zip
S1A_IW_GRDH_1SSH_20150207T043519_20150207T043544_004512_0058A1_FEB5.zip
S1A_IW_GRDH_1SSH_20150219T043519_20150219T043544_004687_005CB0_749C.zip
S1A_IW_GRDH_1SSH_20150408T043519_20150408T043544_005387_006D8A_7DC3.zip
S1A_IW_GRDH_1SSH_20150420T043520_20150420T043545_005562_0071E3_5E98.zip
S1A_IW_GRDH_1SSH_20150502T043521_20150502T043546_005737_0075DF_DC8B.zip
S1A_IW_GRDH_1SSH_20150526T043535_20150526T043600_006087_007E31_01D2.zip
S1A_IW_GRDH_1SSH_20150619T043537_20150619T043602_006437_00883B_D089.zip
S1A_IW_GRDH_1SSH_20150701T043537_20150701T043602_006612_008D15_C99D.zip
S1A_IW_GRDH_1SSH_20150713T043524_20150713T043549_006787_0091F9_7479.zip
S1A_IW_GRDH_1SSH_20150725T043525_20150725T043550_006962_0096F9_D8D7.zip


On the new crack: I noticed that for the first time on a Landsat image from 6th Feb. Seen it since then both Landsat and Sentinel images, developing from a "maybe" to certainly in these latter images.
http://forum.arctic-sea-ice.net/index.php/topic,429.msg44967.html#msg44967

A-Team

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #357 on: August 03, 2015, 05:03:08 PM »
Thanks! The second crack you observed back in February is just barely visible in the 01 Dec 14 Landsat (after beating on it with local adaptive contrast).

Wipneus

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #358 on: August 08, 2015, 03:31:16 PM »
Sequence of two frames, each a combination of two hi-res (IW) Sentinel images, shows the before and after of the recent calving.

crandles

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #359 on: August 08, 2015, 03:55:39 PM »
Is it possible to rotate, scale and align and create blink gif of

http://ichef-1.bbci.co.uk/news/624/media/images/68649000/jpg/_68649121_2013_07_02.jpg

to show where the current calving front on last gif is compared to last time?

Or is this impossible? Too few points not on glacier that are too uncertain as to position on other image? (There seem to be a couple of clearly recognisable features on the south side of the glacier.)
« Last Edit: August 08, 2015, 04:07:23 PM by crandles »

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #360 on: August 08, 2015, 05:37:19 PM »
While I have not developed very good image processing skills, the attached image by Matt Owens, compares the PIIS condition in Sept 2012 to Sept 2013.  When one compares this image with the blink images Wipneus just posted of the PIIS in July - August 2015 it is apparent how far upstream the calving face has migrated.  While the face migration associated with the July 2015 calving leaves substantial buttressing support for the SW Tributary Glacial; I would not be surprised if the next upstream splitting tension (and/or flexural) crack will likely calve still further upstream (particularly because of the active advection of warm CDW currently occurring below the PIIS); which will likely further reduce the buttressing support on the SW Tributary Glacier.
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Wipneus

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #361 on: August 08, 2015, 07:01:04 PM »
Is it possible to rotate, scale and align and create blink gif of

http://ichef-1.bbci.co.uk/news/624/media/images/68649000/jpg/_68649121_2013_07_02.jpg

to show where the current calving front on last gif is compared to last time?

Or is this impossible? Too few points not on glacier that are too uncertain as to position on other image? (There seem to be a couple of clearly recognisable features on the south side of the glacier.)

Could be better, but here is something.

oren

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #362 on: August 08, 2015, 07:06:38 PM »
Wow. What a difference over two years. I was working on some comparison, but my gimp is misbehaving and my skills are low.
It's interesting that the whole retreat is on one side of the flow, I guess this has to do with the pressure from the SW tributary glacier (or maybe something with the flow of warm water underneath).

crandles

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #363 on: August 08, 2015, 08:31:54 PM »
Thank you very much. Large retreat on south side was evident, but trying to rotate in my head to try to figure out how much  the north side had retreated and any changes on north side buttressing was beyond me.

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #364 on: August 08, 2015, 08:42:55 PM »
Thank you very much. Large retreat on south side was evident, but trying to rotate in my head to try to figure out how much  the north side had retreated and any changes on north side buttressing was beyond me.

The large retreat is on the north side.

Edit: I forgot to say how awesome Wipneus' images are.
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solartim27

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #365 on: August 08, 2015, 08:44:33 PM »
It's interesting that the whole retreat is on one side of the flow, I guess this has to do with the pressure from the SW tributary glacier (or maybe something with the flow of warm water underneath).
The first flow in the 2013 picture caused the start of this thread (I think).  The part that is still remaining can be seen upstream of the crack in the 2013 picture, and is grounded on an undersea pinnacle.

I am curious about the new cracks forming, and how long it takes for the next calving event.  Does anyone have the dates for noticing the crack for the 2013 calving?  The current calving was first seen in a post by Wipneus in Oct 2014, and calved several months earlier than AbuptSLR's prediction.

The next crack is visible in this shot from June, but I don't know if that is the earliest
FNORD

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #366 on: August 08, 2015, 11:44:05 PM »
So that others can learn from my mistakes:  In my opinion the primary reasons that my "prediction" of the calving event was off by several months are: (a) I assumed that sea ice would pin the pending iceberg in place longer; however, the strong current El Nino appears to have advected so much warm CDW into the area that the local sea ice looks either fragile or absent; and (b) I had not accurately considered how the basal melting and associated basal changes would allow the pending iceberg to fracture into so many pieces (i.e. while the primary rupture was along the blue line in the first attached image from Reply #221, the secondary along the red line drawn by icefest in Reply #207, came as a surprise to me).

On to projecting the next major calving event: In my opinion the July 2015 calving event has changed the compressive stress field in the PIIS due to the SW Tributary Glacier (see the second attached image from MacGregor 2012); which, leads me to suspect that before any new major calving event occurs we will see a new splitting tension (flexural) crack upstream from the crack highlighted in A-Team's animation in Reply #357.  I believe that this new crack will line-up with the arrow marked "A" in the third attached image by icefest in Reply 217 (note to crandles: the longitude & latitude lines on this image show help you to get out of your NH orientation & into a SH orientation) and that within ½ year of the formation of this new crack formation (say by January 2016) that the new major calving will occur along the crack highlighted by A-Team in Reply #357; which more or less means that I am "predicting" another major calving event in next year's July-August timeframe.  If this occurs, the buttressing on the SW Tributary Glacier will be further reduced.

P.S.: Note that the change in the direction for ice flow in the MacGregor image is due to the compressive stress between the SW Tributary Glacier & the PIIS; and that as the buttresses action of the PIIS progressively degrades in the coming decade, or two, the ice flow direction of the SW Tributary Glacier ice will progressive change to point more upstream.  Thus future splitting tension (flexural) crack will likely migrate upstream from point "A" (at Evans Knoll) in the third attached image, progressively to points further upstream.
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Wipneus

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #367 on: August 09, 2015, 02:07:07 PM »
Here is a different comparison between 2013 and 2015, this time with Landsat 7/8 thermal images. For the Landsat 7 2013 image that is band 6V1, for the Landsat 8 2015 I used band 10.
The 2013 crack is clear without image enhancement. To bring out the 2015 crack I manipulated the contrast somewhat.

solartim27

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #368 on: August 12, 2015, 06:07:18 AM »
Do we need a new thread for Thwaites? 

Sentinel went by again, and I noticed some movement.  I have no idea how this motion compares for ZI or JI up in Greenland, but since PIG remnants show up it's valid to go here.  Here is a GIF from 8/1 to 8/11, and the overview of the area.
FNORD

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #369 on: August 23, 2015, 06:42:01 PM »
The Sentinel image from the 18th shows that the grounded calving split in two.

(click to animate)

solartim27

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #370 on: August 23, 2015, 06:48:10 PM »
Do you see a new crack forming above the old new crack, or is my screen dirty?
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AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #371 on: August 23, 2015, 07:22:33 PM »
Do you see a new crack forming above the old new crack, or is my screen dirty?

First, I would like to thank Wipneus again for providing such outstanding images.

That said:
(a) While I do not yet see a new crack forming upstream of the old new crack; it does appear to me that the old new crack is extending to the southwest, and I am concerned that when the calving front collides with the still grounded iceberg that the new old crack will extend still further to the southwest.
(b) I remark on how little sea ice there is in this area, suggesting that the advection of warm CDW is high at the moment (probably due to the strong and strengthening current El Nino event); and I am concerned that such abnormally strong advection of warm CDW is accelerating basal melting of the ice shelf, and may have contributed to the fracturing of the grounded iceberg.
(c) I am further concerned that if the "old new crack" extends far enough to the southwest then the next major calving event of the ice down stream of the "old new crack" may occur (maybe a year from now) when an ice fracture occurs in the middle of the calving front and normal to the calving face so as to form two new icebergs that can rotate outward from such a hypothetical rupture (normal to the calving front) by pivoting about the northeast and southwest corners of the ice front.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #372 on: August 24, 2015, 09:55:39 AM »
Do you see a new crack forming above the old new crack, or is my screen dirty?

Do you mean A or B?

Open other end.

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #373 on: August 24, 2015, 11:15:13 AM »
Reply #371 was referring to "A" as the "old new crack".
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solartim27

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #374 on: August 24, 2015, 09:14:45 PM »
I circled the area I was referring to.  Sorry for the confusion, should have done that first.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #375 on: August 25, 2015, 12:52:32 AM »
I circled the area I was referring to.  Sorry for the confusion, should have done that first.

Right, or wrong, I do not yet see any crack in the area that solartim27 circled; however, I imagine (based on my understanding of fracture mechanics) that by this austral summer will we likely see a crack immediately upstream of this circled area.  Further, I image that by the July-August 2016 timeframe a new calving event will occur along the crack labeled A.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #376 on: August 25, 2015, 07:53:45 AM »
I circled the area I was referring to.  Sorry for the confusion, should have done that first.

i see it too.  i had to zoom in all the way to see it, and it's clearest on the far right and far left edges, in the middle it seems to disappear completely.  its so faint i would want to see another pic of it to confirm it.... but solartim ur screen cant possibly be dirty!!!! (maybe we both have the contrast settings too high? :) haha just kidding)

AbruptSLR

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #377 on: August 26, 2015, 04:24:27 PM »
The attached Sentinel 1a image of the northeast corner of the PIIS from August 25 2015 shows: (a) minor calving in the "notch" area, and (b) that the calving face of the PIIS is about to contact the grounded iceberg.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #378 on: August 28, 2015, 11:07:23 PM »
The sun has returned so I made a GIF with Sep 14, 2014.  Sort of cloudy, so it's hard to pick a good spot to compare the amount of advancement.  Looks like the calving in the notch has continued, filling in the open water behind the stuck berg.

EDIT:  You can see marks showing a big advance of the southwest (?) tributary glacier, It has been slowly moving over the year, comparing the Sep 14 pic with Apr 1, 2015, but it doesn't look like it has picked up speed since the last PIG calving.
« Last Edit: August 28, 2015, 11:27:46 PM by solartim27 »
FNORD

solartim27

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #379 on: August 28, 2015, 11:40:26 PM »
I zoomed in on the southwest tributary glacier, and added the Apr 1 frame.
FNORD

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #380 on: August 29, 2015, 12:39:51 AM »
I zoomed in on the southwest tributary glacier, and added the Apr 1 frame.

Thanks for the great detective work on the SW Tributary Glacier showing that it has not yet significantly accelerated due to loss of buttressing.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #381 on: August 29, 2015, 01:26:38 AM »
I wish I was as confident as you make me sound.  I think it's too soon after the break to say for sure, and I don't think Modis gives a good enough resolution to say for sure.

It's going to be an interesting austral summer.  Wonder if we'll see melt ponds anywhere, that would be something.
FNORD

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #382 on: August 29, 2015, 01:42:40 AM »
I wish I was as confident as you make me sound.  I think it's too soon after the break to say for sure, and I don't think Modis gives a good enough resolution to say for sure.

It's going to be an interesting austral summer.  Wonder if we'll see melt ponds anywhere, that would be something.

Here is a photo of melt ponds on PIIS circa 2005:
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #383 on: August 31, 2015, 11:02:43 AM »
A new hi-res (IW) image, here rendered at 30m/pix from sentinel is available. The free floating calving has moved out, the grounded part will meet with the glacier soon. Perhaps when the Sentinel is again in the same orbital position: 11th September.

(must click)
« Last Edit: August 31, 2015, 11:10:10 AM by Wipneus »

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #384 on: September 02, 2015, 05:16:25 PM »
For fun I post both the Terra and the Aqua satellite images, respectively, of the PIIS for Sept. 1 2015.  And while it is too cloudy to say for sure, it appears that a limited amount of minor calving is occurring on the calving face near the notch area (northwest end of the calving front), but otherwise, very little change is indicated in the pinned iceberg.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #385 on: September 03, 2015, 11:24:03 PM »
Looks to me like the pinned berg has broken apart, hard to say for sure.
Edit:  Still there on the Aqua image.
« Last Edit: September 04, 2015, 12:49:46 AM by solartim27 »
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #386 on: September 06, 2015, 08:26:21 PM »
I post the two accompanying Terra images both from Sept 5 2015 to show that: (a) the first image shows that the iceberg in front of the PIIS is still grounded and (b) the second image shows that the icebergs that moved away from the PIIS calving front are now locked in sea ice, as is the Thwaites Ice Shelf and residual Ice Tongue.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #387 on: September 11, 2015, 05:26:57 PM »
In the way of an update.  The attached image of the PIIS is by Aqua from the afternoon of September 10 2015, and to me it indicates that the fractured ice field from the "notch" area appears to be in compression now and may be pushing the grounded iceberg, thus preventing the rest of the calving front from making contact with the berg.  If so, this may: (a) slow and/or prevent the reformation of the "notch" until the grounded iceberg is displaced; and (b) increase the span-length contributing to accelerated splitting tension crack extension as the season progresses.
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Wipneus

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #388 on: September 11, 2015, 07:09:27 PM »
The once in 12-day Sentinel 1A update. The grounded calving manages to slide somewhat with the approaching glacier front, keeping the gap still open.

(click to animate)

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #389 on: September 13, 2015, 05:08:00 PM »
While I cannot say for sure, the first attached Aqua image from the afternoon of Sept 12 2015 appears to indicate that the northeastern portion of the grounded iceberg may be fracturing/calving (or this appearance could be the influence of clouds, and/or confusion with sea ice). The second image shows the same photograph with blue contrasts that help to show where the clouds end and the ice begins.
« Last Edit: September 14, 2015, 01:26:34 AM by AbruptSLR »
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #390 on: September 16, 2015, 12:03:29 AM »
The attached Terra image from Sept 15 2015, makes it clear that the grounded iceberg near the PIIS calving front is still intact.
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #391 on: September 19, 2015, 08:57:16 AM »
Landsat season has started!

Here is the first reasonably unclouded image of the southern summer. The width of the split between the grounded calving and the glacier is less than 60m wide.
To my surprise in this mostly untreated image the new crack is NOT visible. Snow? fog? Call in A-team for torturing some data?

(click the picture for a 60m/pix image)

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #392 on: September 19, 2015, 02:56:26 PM »
Comparing with last season's images and applying judicious contrast enhancements brings out the future crack running top-left to bottom-right in the second attached image.

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #393 on: September 19, 2015, 07:33:29 PM »
Comparing with last season's images and applying judicious contrast enhancements brings out the future crack running top-left to bottom-right in the second attached image.

Wipneus,

Thanks for the great images.  It looks to me like the crack/crevasse is likely buried by some recent snowfall.  Also, if you have a chance sometime, could you try to estimate the ice flow speed for the small "Southwest Tributary Glacier" Ice Shelf that is immediately located to the southwest of the PIIS.  While I do not think that this ice flow speed has accelerated yet, it would be nice to have a baseline speed to compare to, should the PIIS calving front retreat far enough in the next few years for the Southwest Tributary Glacier flow speeds to accelerate.

Best,
ASLR

Edit: See Reply #379
« Last Edit: September 20, 2015, 09:01:52 AM by AbruptSLR »
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #394 on: September 20, 2015, 02:25:26 PM »
Quote
Snow? fog? Call in A-team for torturing some data? injudicious contrast enhancements to bring out the crack? buried by some recent snowfall?

I could envision blowing old snow, new snow, or the sun not oriented favorably for crack shadowing (eg, along-crack). While reflectance of incident radiation will vary greatly with wavelength, it is most unusual in Greenland for Sentinel radar to provide better resolution of ground features than cloud-free Landsat.

This is not snow-penetrating radar and a 15 m wide crack would not induce noteworthy polarization effects so it's not clear why Sentinel would see any better under the first two scenarios. However Sentinel sweeps a forward-looking oblique view whereas Landsat looks straight down (nadar view). Only the former sees terrain shadowing (crack depression by edge of crack).

I don't have the Sentinel orbital metadata handy but being in polar orbit, it presumably crosses the image at a slight angle to north-south. This would give it some terrain shadowing of the track because it has a goodly east-west component. It's always a good idea to draw a line on in the image showing the orbital track if there has been re-projection.

Meanwhile, metadata on the 18 Sep 15 Landsat above (LC82321132015261LGN00) shows fairly extreme sun elevation and azimuth. As indicated in the second image below, Landsats at EarthExplorer arrive re-projected to a local Mercator patch with north still up for Antarctica.

Sun Elevation     6.4º
Sun Azimuth    57.6º

Such a low sun angle is normally extremely favorable for showing slight variations in landscape elevation but here the odd azimuth may undo that benefit by more or less aligning with the crack, causing it not to be shadowed. Here the operative azimuthal convention has 180º due south. This makes it much harder to tweak contrast usefully while at the same time not introducing artifacts (first image).

The crack is barely visible in minimally enhanced band 8 of this Landsat (equilization). It can be drawn out somewhat by an adaptive contrast enhancement series, and perhaps more with a northeasterly shadowing convolution or embossing/bump map step. Note the azimuthal shadowing direction is quite apparent in the ridging.
« Last Edit: September 20, 2015, 08:01:18 PM by A-Team »

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #395 on: September 20, 2015, 08:24:30 PM »
There was a sentinel shot over part of the area, so I wanted to look at what I had called the 'new new crack' above.  On a whim I tried an image enhancement, here is the result in a gif.  I believe it is the grounding line we are looking at, as it can be seen to extend clearly past the area I had circled.  Could it be that a combination of glacier advancement with extreme tidal fluctuations is what results in the ridges and cracks?

You'll need to click the lower image to see the enhanced image gif.

Edit, added the enhanced still image.
FNORD

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #396 on: September 22, 2015, 09:14:42 PM »
solartime27,

If you are correct, then the images that you show may indicate that the "new new crack" extends all the way to the northeast side of the PIIS.

Separately,

Attached is a relatively clear Terra image for Sept 22 2015, showing that the main calving front is about to make contact with the grounded iceberg.

Best,
ASLR
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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #398 on: September 25, 2015, 05:07:29 PM »
SAR penetrates deep into a dry snowpack, at C-band we are talking meters of even tens of meters.

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Re: Pine Island Glacier (PIG) Calving and Discussion
« Reply #399 on: September 26, 2015, 01:40:46 PM »
This latest Landsat image, natural color pan-sharpened to 15m/pixel, shows that the gap between glacier en grounded calving has about closed. The very bright stuff near the "contact spot" may be the result of the collision.