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Adam Ash

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Re: PIG has calved
« Reply #1000 on: May 31, 2019, 01:42:16 PM »
The PIG may have thinned sufficiently to have become less brittle. Local crevasses may provide local stress relief, slowing the formation of full-width crevasses.     

...and in thinning, absorbed more heat too.  No?  And if so warmed toward its melting point, then, along with all the ice in the warming world, has it not become weaker, and more prone to structural mush-failure? 
And if a glacier fragments via structural failure rather than by melting, does not a one tonne block of floating fragmented ice (no matter how many degrees below its melting point it is) raise sea level by the same amount as that one tonne of ice will when it is melted?

Does this effect then lead to the observed meltwater pulses, whereby there is one metre sea level rise every 20 years for 500 years or so (entailing vast armadas of ice being washed into oceans by a relatively small amount of meltwater) followed by a pause while all that floating ice melts (hence slowing atmospheric warming trends), followed again by another ice-heating-to-structural-failure phase; mix and repeat until we have 70 metres of sea level rise '...in a timeframe inconceivable to man' [Hansen, Storms of our Children].   Mmmm?

b_lumenkraft

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Re: PIG has calved
« Reply #1001 on: June 10, 2019, 08:43:29 PM »
Not sure about that but i'm having the impression new cracks are forming.

IceConcerned

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Re: PIG has calved
« Reply #1002 on: June 13, 2019, 11:07:17 AM »
On the Western side, I have the impression that the crack have a path all the way to the open waters

Wipneus

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Re: PIG has calved
« Reply #1003 on: June 13, 2019, 06:48:32 PM »
Time for an update. Cracks are developing slowly and are becoming visible in the modes with lower resolution. Here is is EW, medium resolution: 40m. The higher resolution modes have a basis resolution of 10m.

The animation is 80m/pix resolution. Horizontal and vertical polarization of the reflected microwave radiation are code as Green and Blue.

Stephan

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Re: PIG has calved
« Reply #1004 on: June 13, 2019, 09:51:36 PM »
Thank you for that wonderful animation.
On the SW edge of the glacier (left upper corner) one of the cracks has significantly widened. A major calving in July 2019 to be expected?

Tony Mcleod

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Re: PIG has calved
« Reply #1005 on: June 14, 2019, 06:44:42 AM »
What is the width of the calving front?

Rich

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Re: PIG has calved
« Reply #1006 on: June 14, 2019, 08:15:32 AM »
What is the width of the calving front?

I think approximately 50km.

Wipneus

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Re: PIG has calved
« Reply #1007 on: June 14, 2019, 08:35:35 AM »
What is the width of the calving front?

Width (and height) of the image is 700*80 = 56000m or 56 km.

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Re: PIG has calved
« Reply #1008 on: June 14, 2019, 04:47:21 PM »
...which then calculates (eyeballing-wise) to speeds of the calving front between 11 and 13 m/day.

Wipneus

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Re: PIG has calved
« Reply #1009 on: June 18, 2019, 10:27:20 AM »
minor calving.

Stephan

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Re: PIG has calved
« Reply #1010 on: June 18, 2019, 09:10:13 PM »
Thank you for that wonderful animation.
On the SW edge of the glacier (left upper corner) one of the cracks has significantly widened. A major calving in July 2019 to be expected?
This is exactly the crack I mentioned, that calved today.
In my opinion this is the worst place for a calving because upstream of this location there are a lot of cracks and icebergs instead of a homogeneous ice sheet (like further NE of that edge).
Is this a start of a speeding up of PIIS decomposition?

oren

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Re: PIG has calved
« Reply #1011 on: June 18, 2019, 09:26:07 PM »
In my layman's view, it's a bad place for calving because it increases the distance of the PIG to the Thwaites tributary glacier, and further decreases any hopes of buttressing between them. It's also somewhat expected, as once the buttressing was lost the east side of the PIG was supposed to speed up a little.

IceConcerned

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Re: PIG has calved
« Reply #1012 on: June 19, 2019, 04:18:25 PM »
I also think this is a ad place to lose ice : the back pressure of this block helped maintain in place the cracked ice just south of it. On Wipneus animation we can even see the two immediate next crack increase markedly in size.
Besides, losing the W anchor should facilitate the movement of the big calving block, thus creating a kind of rotation that will amplify stresses at the last remaining non cracked ice on the eastern side.

IceConcerned

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Re: PIG has calved
« Reply #1013 on: June 27, 2019, 01:11:25 PM »
I just checked GFS, is it normal in this season (winter solstice in SH) to have such warm blobs near the continent ? (here views for today and Monday)
It will certainly do no good to the glaciers there

Stephan

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Re: PIG has calved
« Reply #1014 on: July 11, 2019, 10:07:53 PM »
Any news from "my pet glacier" from downunder?

b_lumenkraft

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Re: PIG has calved
« Reply #1015 on: July 11, 2019, 10:14:23 PM »
Nah, Stephan, not really.

I'm always thinking i see new cracks evolving upstream. But not really, could also be dunes or something.

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Re: PIG has calved
« Reply #1016 on: July 16, 2019, 03:08:35 PM »
Hi-res (10m/pix) detail of the two big cracks. I'd say that they have widened considerably in the 12 days between the two images.  Any time now...

Images have been aligned with the movement of the ice upstream of the cracks.

Stephan

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Re: PIG has calved
« Reply #1017 on: July 16, 2019, 07:17:05 PM »
Thank you for this update.
Any bets concerning the date of the next major calving?

I would go for 10-15 August...

Wipneus

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Re: PIG has calved
« Reply #1018 on: August 09, 2019, 08:48:20 AM »
The cracks are still widening as this detail shows.

Tor Bejnar

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Re: PIG has calved
« Reply #1019 on: August 09, 2019, 05:24:20 PM »
Wip,
There is (appears to be) a valve that opened in the crack at the bottom of that GIF.   What are 'you' letting out ...OR... What have you unleased on the world?  :o
Arctic ice is healthy for children and other living things.

blumenkraft

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Re: PIG has calved
« Reply #1020 on: August 09, 2019, 06:00:24 PM »
Wip,
There is (appears to be) a valve that opened in the crack at the bottom of that GIF.   What are 'you' letting out ...OR... What have you unleased on the world?  :o

What are you even talking about, Tor. It's obviously a handshake.  ;D ;)
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paolo

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Re: PIG has calved
« Reply #1021 on: August 13, 2019, 02:12:01 PM »
minor calving.

Stephan

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Re: PIG has calved
« Reply #1022 on: August 18, 2019, 08:16:41 AM »
Thank you for this update.
Any bets concerning the date of the next major calving?

I would go for 10-15 August...
I probably was wrong ?!?

Wipneus

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Re: PIG has calved
« Reply #1023 on: September 03, 2019, 09:52:14 AM »
Update, compare with https://forum.arctic-sea-ice.net/index.php/topic,429.msg220359.html#msg220359

Crack keeps getting wider, very fast in comparison with usual speeds.

Stephan

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Re: PIG has calved
« Reply #1024 on: September 03, 2019, 09:23:10 PM »
Are both images taken from the same day as the indicated date show?

blumenkraft

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Re: PIG has calved
« Reply #1025 on: September 03, 2019, 09:38:16 PM »
I suspect there would be at least one/two weeks difference between those?
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oren

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Re: PIG has calved
« Reply #1026 on: September 03, 2019, 09:41:50 PM »
I believe it's 20-8 compared with 08-8.

Stephan

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Re: PIG has calved
« Reply #1027 on: September 03, 2019, 10:30:36 PM »
I believe it's 20-8 compared with 08-8.

It can't be 08-8 because the structure at the very bottom of the image looks different from Wipneus' last crack posting (08-8) four weeks ago. It must be a later date.

oren

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Re: PIG has calved
« Reply #1028 on: September 03, 2019, 10:36:09 PM »
Oops...

Wipneus

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Re: PIG has calved
« Reply #1029 on: September 04, 2019, 04:07:09 PM »
Sorry for the confusion. The images are 2019-08-20 and 2019-09-01 (12 days is the return time of the Sentinel satellite for the same orbital position).

blumenkraft

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Re: PIG has calved
« Reply #1030 on: September 09, 2019, 08:48:00 AM »
Open waters in front of PIG as the first rays of sunlight hit.

Sentinel-3 SLSTR
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Phil42

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Re: PIG has calved
« Reply #1031 on: September 11, 2019, 10:53:21 AM »
Another view of the open water adjacent to the calving front.

https://worldview.earthdata.nasa.gov/?v=-1837537.4088698481,-479079.84330135013,-1346017.4088698481,-208487.84330135013&p=antarctic&t=2019-09-10-T08%3A49%3A38Z

While surely not healthy, this doesn't seem to be too untypical for this time of the year when looking at the last few years on Worldview.


Stephan

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Re: PIG has calved
« Reply #1032 on: September 12, 2019, 10:10:04 PM »
With the first new pictures in this austral spring from EOSDIS Worldview I estimated the movement of the calving front of PIIS from Feb 03, 2019 to Sep 10, 2019 (= 219 days). According to the actual position the front has moved in this time period by around 2.4 km, which equals to 11 m/day for this time period (checked at two different positions)

Wipneus

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Re: PIG has calved
« Reply #1033 on: September 15, 2019, 11:12:36 AM »
First visible light images from Sentinel 2 of the Pine Island Glacier.
The first image present the overview in reduced resolution (50m/pix). Then a detail in the native resolution of 10m/pixel.

blumenkraft

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Re: PIG has calved
« Reply #1034 on: September 15, 2019, 11:21:21 AM »
That's odd. EQ-Browser shows them but Playground doesn't.  ???
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Jim Hunt

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Re: PIG has calved
« Reply #1035 on: September 15, 2019, 01:45:20 PM »
Thanks Wipneus.

That's odd. EQ-Browser shows them...

I assume you mean EO?

https://www.sentinel-hub.com/explore/eobrowser
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blumenkraft

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Re: PIG has calved
« Reply #1036 on: September 15, 2019, 01:48:09 PM »
Yeah, that's what i mean. :)

Thanks for the correction, Jim.
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Stephan

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Re: PIG has calved
« Reply #1037 on: September 15, 2019, 09:55:44 PM »
Wipneus, thank you very much.
Could you give me a link to that Sentinel B source - if I open this programme, there is no actual photograph available (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-75.17015590641843&lng=-101.28536224365234&zoom=11&preset=1-NATURAL-COLOR&layers=B01,B02,B03&maxcc=100&gain=0.2&gamma=1.0&time=2018-08-01%7C2019-02-16&atmFilter=&showDates=true)

A lot has happened since last February. I compared some of the structures and I find a lot of new cracks, and the already existing ones have massively widened. I am especially concerned about the SW edge of PIIS, because there is already a lot of broken-up stuff which is now only a few kilometers away from the calving front. Must we expect a destabilisation of the whole ice sheet in the coming austral summer?

AbruptSLR

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Re: PIG has calved
« Reply #1038 on: September 15, 2019, 11:12:12 PM »
...
Must we expect a destabilisation of the whole ice sheet in the coming austral summer?

The is almost no chance of the whole West Antarctic Ice Sheet becoming unstable this coming austral summer, as the pending major calving event for the PIIS should leave plenty of ice shelf left to continue to buttress the PIG.
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Wipneus

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Re: PIG has calved
« Reply #1039 on: September 16, 2019, 07:04:01 AM »
Wipneus, thank you very much.
Could you give me a link to that Sentinel B source - if I open this programme, there is no actual photograph available (https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-75.17015590641843&lng=-101.28536224365234&zoom=11&preset=1-NATURAL-COLOR&layers=B01,B02,B03&maxcc=100&gain=0.2&gamma=1.0&time=2018-08-01%7C2019-02-16&atmFilter=&showDates=true)


Stephan, I list and download from ESA's scihub using scripts provided by them.
The full flename of the download is:
S2B_MSIL1C_20190914T151259_N0208_R139_T14CMB_20190914T180019.zip
of use may be the productid:
'3ddd27b9-4efa-4bfb-a5b8-22cb80cd0662'

nukefix

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Re: PIG has calved
« Reply #1040 on: September 16, 2019, 10:14:07 AM »
It is also possible to download Sentinel-1/2/3 data with the ESA SNAP toolbox:

https://step.esa.int/main/toolboxes/snap/

Stephan

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Re: PIG has calved
« Reply #1041 on: September 16, 2019, 10:37:08 PM »
...
Must we expect a destabilisation of the whole ice sheet in the coming austral summer?

The is almost no chance of the whole West Antarctic Ice Sheet becoming unstable this coming austral summer, as the pending major calving event for the PIIS should leave plenty of ice shelf left to continue to buttress the PIG.

I, of course, didn't mean the whole WAIS but the PIIS itself. Sorry for having mixed up Ice Shelf with Ice Sheet...

gerontocrat

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Re: PIG has calved
« Reply #1042 on: September 17, 2019, 09:21:00 PM »
The data on the Pine Island Glacier comes from a Jan 2019 Paper - https://www.pnas.org/content/116/4/1095
Four decades of Antarctic Ice Sheet mass balance from 1979–2017

They have extracted from a mass of previous studies, and they are confident enough on discharge data to produce analyses by years for data on nearly 200 sub-regions of Antarctica. But the SMB (mainly snowfall) data is not analysed by year, there are only 39 year totals.

But I am not a scientist worried about peer review. So on the attached graphs I have allocated SMB over years by the yearly average. I did this to show how a relatively small percentage annual increase in discharge leads to a high percentage increase in net mass loss.

In the 39 years of the analysis, discharge is estimated at nearly 4,000 GT, but with nearly 3,000 GT of SMB gain, net mass loss is just over 1,000GT. Half of that may well have happened in the first 30 years, half in the last 9 years.

The current annual net mass loss guesstimate is 65 GT a year. A pure guess at the future gives that increasing to over 100 GT per year in 10 years.
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Stephan

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Re: PIG has calved
« Reply #1043 on: September 19, 2019, 10:00:58 PM »
I used the latest Sentinel picture from PIIS (Sep 14) and compared it with the one from Feb 20, 2019. I applied the following colour code:
blue: Calving front on Feb 20, adjusted to the movement of the whole ice shelf
green: Widened cracks
red: new cracks
dotted red: possible new features on SW tributary, but they are maybe only visible now because of the lower sun angle and not caused by changes of the glacier itself.
yellow: "Zone of destruction". The NE part moves much faster than the SW edge (which seems to be almost stationary), therefore the ice in-between looks like having been constantly under big shear stresses with dozens of new cracks and smaller pieces than before.

See attached picture

Stephan

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Re: PIG has calved
« Reply #1044 on: September 19, 2019, 10:12:56 PM »
The same for the NE part of the PIIS, with much less changes compared to Feb 20. Same colour code than last posting, the magenta circled iceberg looks like a "calving product" of PIIS.

Stephan

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Re: PIG has calved
« Reply #1045 on: September 23, 2019, 08:53:07 PM »
I analyzed the movement rate of the PIIS at different spots on PIIS and the SW tributary in the time between Feb 06 and Sep 14, 2019. The speed is comparable to that of last austral autumn and ranges between 11 and 16 m/day on the PIIS and is much slower on the SW tributary.

See attached figure.
« Last Edit: September 23, 2019, 09:43:14 PM by Stephan »

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Re: PIG has calved
« Reply #1046 on: September 26, 2019, 09:37:24 AM »
Progress report: cracks are extending and widening everywhere. Animation ( images should differ 12 days) scaled to 50m/pix for an overview. Images are aligned at the glacier front.


Stephan

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Re: PIG has calved
« Reply #1047 on: September 28, 2019, 09:52:20 PM »
Mini calving on SW tributary
I compared the Sentinel images of Sep 27 with the ones from Sep 14.
A minor (or micro?) calving (area ca. 500 x 300 m) has occurred in-between this time frame

See attached picture

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blumenkraft

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Re: PIG has calved
« Reply #1049 on: October 03, 2019, 08:41:00 PM »
Wow, you can see it growing in this comparison. That must be hundreds of meters in only a few days, right?
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