Author Topic: Pine Island Glacier (PIG) Calving and Discussion (Read 744821 times)

baking · « **Reply #1300 on:** December 14, 2019, 02:30:43 PM »

Scientists on the ground yesterday playing with radar saying the grounding line may not be where you think it is: https://twitter.com/geologicalJo/status/1205753120430710784

"lots of radar data suggesting a new grounding line exists around Evans Knoll"

I'm reading this to say that "around" means Evans Knoll is now in island, just like the old "pinning point" 30 km downstream.

paolo · « **Reply #1301 on:** December 14, 2019, 03:27:18 PM »

Probably, you equivocally, the area I marked as "Kaput” is not grounding!
The pinning point is given by the grounded area + a strip of ice shelf.
See the attached image
We have nothing better at our disposal!

And, according to the twitter, the grounded area is currently even smaller (this don't I was afraid from the information about the melt of the article D.E.Shean et al. 2019, see post 1284 fourth image)

Conclusion: getting better and better....

Waiting for this new information

gerontocrat · « **Reply #1302 on:** December 14, 2019, 05:12:47 PM »

PIG and Thwaites seafloor retrograde slope worse than thought. (farther inland and deeper)

Article spotted by blumenkraft
https://forum.arctic-sea-ice.net/index.php/topic,622.msg240698.html#msg240698

https://www.awi.de/en/about-us/service/press/press-release/antarcticas-delicate-face.html
Antarctica’s Delicate Face
A new map reveals the landforms hidden beneath the ice in unprecedented detail. This will support more accurate forecasts concerning the future of the glaciers and sea-level rise.

Quote

“Thanks to the new map, we can now more accurately predict in which regions the glaciers are especially vulnerable to climate change,” says Olaf Eisen. For example, they now know that, on West Antarctica’s Thwaites Glacier and Pine Island Glacier, the terrain slopes farther and deeper inland than previously assumed. For these glaciers, which ice experts already considered to be ‘problem children’, the future now looks even bleaker. But such areas with problematic topographies can also be found in East Antarctica, e.g. the massive Recovery Glacier, which drains 40 percent of East Antarctica. And the record-breaking troughs below Denman Glacier could also contribute to its destabilisation.

That being said, the insights offered by the new map aren’t all bad news. For example, previously undiscovered ridges could help to stabilise the ice flowing over the Transantarctic Mountains. As a result, these ice masses may be able to withstand climate change longer than previously projected. “These new findings will help us to better assess the stability of glaciers in various regions,” Eisen concludes. “Only then can we realistically estimate whether, and if so, by how much they could cause the sea level to rise.”

paolo · « **Reply #1303 on:** December 15, 2019, 02:55:29 PM »

Low resolution image of Sentinel 1
The world of shadows
It seems to me to be acting like the clairvoyant
Moreover, even if they are real, the opening of a crack can stop the development of a competing crack
The marks are above the possible cracks

To be taken or left according to your feeling.
In any case, it doesn't seem very strong to me.

More seriously, if I have time, I would like to evaluate the speeds to analyze more generally and more seriously what is happening. I'll keep you informed.

Click to enlarge the image

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

paolo · « **Reply #1304 on:** December 16, 2019, 03:13:09 PM »

Since no one is talking about it, a small piece has come off the future iceberg

Stephan · « **Reply #1305 on:** December 16, 2019, 06:01:11 PM »

This mini-calving is somewhat surprising as the latest Sentinel image (03.12.2019) does not give any indication (cracks etc). Thnk you for posting this.

paolo · « **Reply #1306 on:** December 18, 2019, 03:37:57 PM »

Today's images are not very good (Sentinel 1 low resolution and very black)

The iceberg connections with PIG and SWT still hold.
The fractures in the iceberg itself are growing and multiplying.
What does it do to hold?

I will report only (images attached; to zoom in the second click):

- small events related to SWT

- a possible future rift in PIG, it continues an existing rift (SSM) : the image is borderline, it may be that there is nothing (to follow).
I have the impression that there are future crackers further upstream, but the images are too confusing and I don't want to report anything at the moment.

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

Wipneus · « **Reply #1307 on:** December 22, 2019, 10:06:55 AM »

Surface melt blackens the Sentinel 1's radar images. Some finer cracks become visible in this (medium resolution) dual polarization (Red=horizontal,Green=vertical) image. Needs a click to show in native (40m/pix) resolution.

paolo · « **Reply #1308 on:** December 22, 2019, 11:34:42 AM »

Nothing to notice, but...

crandles · « **Reply #1309 on:** December 22, 2019, 11:43:15 AM »

Quote from: paolo on December 22, 2019, 11:34:42 AM

Nothing to notice, but...

That looks like third piece in a series that have/are being lost. 2 others just above it.

The 2 above seem to have allowed further rotation by the cork and these two pieces sliding past each other a little. Red and orange lines added were adjacent (certainly for red lines, less sure about orange). I am not sure I see much scope for this continuing with this latest piece or with further such slices off the cork but who knows, I certainly don't.

Hmm. Looking back I see the two pieces had already broken off by 14 September, so perhaps it is a bit of a stretch to suggest this latest crack is one of the same series.

blumenkraft · « **Reply #1310 on:** December 23, 2019, 05:39:49 PM »

Via Sentinel 3, 22. vs 23.

Stephan · « **Reply #1311 on:** December 23, 2019, 05:46:21 PM »

Hi blumenkraft,
I just detected this calving on EOSDIS worldview and wanted to post it here.
Thank you for posting this.
I think this calving is important for the future stability of the SW tributary. As far as I know this ice sits on an underwater ridge, south of it there is a deep trough where the SW tributary flows. I wonder whether the ice edge now sits on a prograde bed or whether the highest part of this underwater ridge has already passed.

Check out the comparison between Nov 11 and Dec 23: https://worldview.earthdata.nasa.gov/?v=-1692481.203307675,-385941.80992529297,-1525569.203307675,-296725.80992529297&p=antarctic&t=2019-11-11-T00%3A00%3A00Z&t1=2019-12-23-T00%3A00%3A00Z&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&l1=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&ca=false&cv=5

blumenkraft · « **Reply #1312 on:** December 23, 2019, 05:51:32 PM »

Quote from: Stephan on December 23, 2019, 05:46:21 PM

I just detected this calving ... and wanted to post it here.

First!

You are very welcome Stephan. Sentinel 2 shots should come in soonish and it looks like they will be cloud-free. Very looking forward to those.

paolo · « **Reply #1313 on:** December 23, 2019, 07:44:36 PM »

So I was right to ask if he was going to calve before the iceberg (post 1306)

Stephan,
to answer your questions, I'll call back and join again:

- my animated gif (post 1285) that I join again (animation generated from an image with the bathymetry +grunding line 2011 and an image of the elevations +grunding line 1996).
Click to animate.

- my image (post 1283) related to the bathimetry of NIS, PIG and SIS with in particular the SWT, in which we see the bathymetry of the SWT upstream.
Click twice to zoom in.

The grunding line is already beyond the first ridge (about -750m and corresponding to a strait, relatively to -700m, to be taken into account for CDW infiltrations).
There are still two ridges (about -750m) and then the bottom is retrograde and the warm CDW will attack the Thwaites Glacier.

Moreover the SWT no longer has the PIG as pinning point, only the pinning point on the left and what is left of the SIS ...

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

Stephan · « **Reply #1314 on:** December 23, 2019, 07:58:46 PM »

Thank you for reposting the maps again. I tried to identify today's calving position and I think I have caught it. It is within the area that is already floating, close to the "nose" of the grounding line's position 1996, where the yellow line separates from the grounding (red) line, below is the -600 bathymetry line. So there is an even, slightly retrograde bed further south of today's calving position. I wonder what happens now to the other cracks on SWT close to the cork, and later to the stability of SWT (after the cork has calved).

PS: Is there any actual grounding line map available?

Wipneus · « **Reply #1315 on:** December 23, 2019, 07:59:04 PM »

A clear Landsat 8 image, with low solar elevation (8.2 degrees) shows more and more thin cracks have developed.

Click to see in full resolution (15m/pix).

paolo · « **Reply #1316 on:** December 23, 2019, 08:33:44 PM »

Stephan,
it is parallel to the green line, on a line passing approximately through the cross in the dark blue area (between -700 and -900). So nothing to do with the grunding line, which, relative to the flow, is much further upstream (you can go from the pinning point on the left of the SWT).
It's after passing the two ridges, that I mentioned earlier, that the bottom quickly reaches less than -1000m.

To my knowledge there is no article about line grunding after 2011 (there is an article with elements about line grunding for the PIG relative to 2015 but only for the PIG).

I join again the image (post 1284) relative to the calculated quantities of basal melting (click to zoom in).

What's interesting is how fast the rift opened, the 06/12 was opening as you can see in the picture I communicated that day (post 1244) that I'm joining again (this post also contains two zoom of this picture).
It is also interesting to note, as we can easily deduce from this image, that in this case it is not a fracture that opens, but a base channel that opens up to the surface with the collapse of the bridge between the two sides.

Andreas T · « **Reply #1317 on:** December 23, 2019, 08:47:36 PM »

The group investigating the geology east of PIG report new radar measurements of grounding line around Evans Knoll, near the eastern end of the calving zone. Taken by sledge from the surface they are probably very localized
https://twitter.com/geologicalJo/status/1205753120430710784

Stephan · « **Reply #1318 on:** December 23, 2019, 08:50:41 PM »

Thank you paolo for this clarification.
As blumenkraft announced before, there is a new Sentinel image available. I present the analysis of the actual picture in comparison to the picture from Dec 07, 2019 (at that time I also had noticed and posted the new crack).
Colour code:
light blue = grounded icebergs
green = fresh calving events (also at the "tip" of the SW Tributary !)
red = new or lenghtened/widened cracks
yellow = a new area of destruction (the SWT moves northward whereas the ice west of it seems almost stationary (black dotted line shows the boundary, noted as "stable ice area"). The friction between these two ice masses causes a lot of cracks, comparable to the situation SE of the "Cork" in PIIS)

See attached picture

Stephan · « **Reply #1319 on:** December 23, 2019, 09:08:25 PM »

New development at the NE end of PIIS.
Four mini calvings (green circles) and a new crack (red line) below Evan's Knoll show that there is a lot of tension ... and action to begin [very] soon.

See attached picture.

paolo · « **Reply #1320 on:** December 23, 2019, 09:12:10 PM »

Stephan ayant déjà posté pour le SWT je poste uniquement pour le Cork et sur les cracks au sud du PIG (seulement le premier a bougé)

Andreas T
et pour avoir les informations il faudra attendre la publication..

paolo · « **Reply #1321 on:** December 23, 2019, 09:32:16 PM »

To finish a zoom on the rifts

(click to zoom in)

Stephan · « **Reply #1322 on:** December 23, 2019, 09:49:35 PM »

New development at the eastern edge of the SW Tributary.
The long existing cracks have lengthened and widened (red lines). The counterclockwise rotation of the Cork has continued. The movement direction of the SW tributary is marked by the yellowish green arrows. The calving zone of today left above (circled in green).

Stability looks differently...

See attached picture.

paolo · « **Reply #1323 on:** December 23, 2019, 10:03:07 PM »

Wipneus has already shown the longitudinal cracks in the iceberg.

I want to add two images related to the extension of the two cracks that start from the edge
You can imagine that once he calves or even before he calves he'll be all broken up...

Stephan · « **Reply #1324 on:** December 23, 2019, 10:15:57 PM »

Action and further destruction in the SW part of the PIIS as well.
I compared the images between Dec 07 and Dec 23. The differences are marked in red (new or lengthened / widened cracks) and in white (completely tumbled over and destroyed iceberg). The flow direction is indicated by yellowish green arrows. The zone of destruction grows and the destruction is more and more complete. The cork mustn't break to prevent that all that ice mélange is set free. Hope it holds for a while...

See attached picture.

Stephan · « **Reply #1325 on:** December 23, 2019, 10:47:11 PM »

Action also at the eastern end of the PIIS/PIG (the "blumencrack area").
The comparison shows the birth of a new zone of destruction (circled yellow) with a lot of fast widening cracks and many icebergs, held loosely together by sea ice. All relevant growing and lengthening of cracks are marked in red. The dashed pale line is approx. the grounding line (GL) from 10-20 years ago. The yellowish green arrows show the flow direction.

Having had the discussion earlier in this thread, could these features (or the change of these features) on the surface give information about the actual position of the GL? From Eric Rignot's presentations I heard how damn complicated it is to reliably find out the exact position of the GL.

See attached picture.

paolo · « **Reply #1326 on:** December 24, 2019, 12:00:21 AM »

Stephan,
Once the iceberg has calved, the "Cork", if it doesn't break off at that time, won't be able to stay in place for long anyway. The next piece won't be able to assume this function (it doesn't have the physical configuration to do so) and behind it there's nothing left.
It will take time, it's a dense mix of big pieces, but it's inevitable: this whole area will empty. The SIS is not moving fast enough to stop it, and even if it was moving faster the PIG would end up breaking it again (the PIG is moving too fast to hope for anything else). It is unstoppable
This area is fed by a tributary which will be destabilized too (and behind it is the TWG which in the future could suffer from it).

Finding the grunding line is very difficult, normally it requires interferometry between high-resolution radar images corresponding to identical passages very close to each other (one must determine the subsidence and the uplift induced by the tides), so having a suitable satellite and making it available to the scientists (for example for the calculation of the grunding line of the PIIS part related to the PIG in 2015, and limited to this part, they used the COSMO-SkyMed satellite, and in particular two satellites of the COSMOS satellite constellation which allow for two acquisitions one day apart, and with campaigns lasting several days; I would post information related to this article). It cannot be deduced from an image of the surface (from these images one can deduce only areas that almost certainly do not float: uplift that cannot be explained otherwise).

Small remark: we can't really use the term PIIS, which includes NIS, SIS and the "PIG" component, to design only this component. For this reason, I use the PIG notation also for this component, which is also incorrect. Some authors use the term "Main Ice Shelf" or "Central Ice Shelf" which are correct, but I believe that this term would cause confusion in this forum (I don't use them for that reason). We would have to find a term that is appropriate for everyone.

PS: In the last post (1325) the PIG annotation at the top right disturbs me a little bit, at the limit, by not being able to position it upstream of the big yellow arrow (out of the frame), it could have been put completely at the bottom.
And a thank you for all your work on the last image of Sentinel 2.

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

baking · « **Reply #1327 on:** December 24, 2019, 04:48:37 AM »

I haven't seen anyone post anything specifically about the Northern end of the main crack today, so here is a comparison with December 7, the last previous clear image. There is a slight rotation probably due to different satellite orbits, but with the weather as bad as it's been, you can't be picky about orbits.

blumenkraft · « **Reply #1328 on:** December 24, 2019, 08:12:01 AM »

Quote from: Stephan on December 23, 2019, 09:08:25 PM

Four mini calvings (green circles)

Damn, i saw this one on the low-res SAR but wasn't sure so i didn't post it. This is the one in question.

Link >> http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201912/S1B_EW_GRDM_1SSH_20191222T041104_B949_S_1.8bit.jp2

blumenkraft · « **Reply #1329 on:** December 24, 2019, 08:42:50 AM »

Quote from: Stephan on December 23, 2019, 10:47:11 PM

(the "blumencrack area").

LOL, never thought this term gets adopted...

Anyway, i feel honoured, Stephan. Thanks for that.

So, suppose the grounding line is behind the line you draw it. That would cause the area behind the cracks to slowly start to float. Since this part of the shelf is thicker than the floating part, it would elevate higher, would cause cracks at the points where the cracks are... Right?

oren · « **Reply #1330 on:** December 24, 2019, 03:25:50 PM »

Thanks for all the recent updates. The PIG really looks bad. I am very surprised the big one hasn't calved yet, but overall the cracks and destruction zones seem more prevalent (and of course more inland) than they used to be.

Stephan · « **Reply #1331 on:** December 24, 2019, 04:41:13 PM »

Quote from: oren on December 24, 2019, 03:25:50 PM

Thanks for all the recent updates. The PIG really looks bad. I am very surprised the big one hasn't calved yet, but overall the cracks and destruction zones seem more prevalent (and of course more inland) than they used to be.

You're welcome. It's my "pet glacier". And I feel I need to notice and post in which (bad) state it is. I can't help him from here - apart from living as CO₂ neutral as possible...

paolo · « **Reply #1332 on:** December 24, 2019, 05:34:43 PM »

Baking,
your post intrigued me: "here is a slight rotation probably due to different satellite orbits"
two different orbits can produce local motion, but not rotation, and if the iceberg is effectively turning, the PIG itself can't be turning.
I wanted to check by taking the image of the 23/11 and we can verify that what you took for a rotation is the combined effect :
- of a rotation of the iceberg.
- of a speed differential between the centre of the flow and its edges.
See also the attached animation ( twice click)

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

baking · « **Reply #1333 on:** December 24, 2019, 07:56:52 PM »

Nice catch, paolo.

blumenkraft · « **Reply #1334 on:** December 24, 2019, 10:14:16 PM »

There are melt ponds on top of those rotated icebergs in the middle of the big crack!

3. vs 23.

HapHazard · « **Reply #1335 on:** December 24, 2019, 10:43:14 PM »

Now that's cool. (OK, warm)

grixm · « **Reply #1336 on:** December 24, 2019, 10:47:32 PM »

It seems there is prime conditions for calving right now. Both mild temperatures and strong wind downglacier. When comparing the worldview pictures from today and yesterday, we see:

1) Darkening of the rifts and some nearby ice, indicating melt like also shown in blumenkraft's gif.
2) Sea ice around the glacier has been pushed north, a lot of fast ice has even been ripped loose.
3) It looks a bit like the calving front has even moved/rotated more than usual, especially near the hook tip, but the resolution of the images is too low to be sure.

These conditions will persist tomorrow but after that it will get cooler and calmer. Forecast here: https://www.yr.no/en/forecast/graph/2-6623299/Antarctica/Pine%20Island%20Glacier

blumenkraft · « **Reply #1337 on:** December 25, 2019, 06:39:15 AM »

New Moon: 26.12.2019, 06:13

#justsaying

blumenkraft · « **Reply #1338 on:** December 25, 2019, 06:41:53 AM »

Quote from: grixm on December 24, 2019, 10:47:32 PM

1) Darkening of the rifts and some nearby ice, indicating melt like also shown in blumenkraft's gif.

Even more apparent in the radar shots. Some of them in recent days show some areas pitch black as if it was ocean.

blumenkraft · « **Reply #1339 on:** December 25, 2019, 10:17:01 AM »

New crack at a significant location.

Any time now...

Link >> http://bslmagb.nerc-bas.ac.uk/iwsviewer/?image=DataPolarview/111_S1jpeg2000_201912/S1B_IW_GRDH_1SSH_20191225T043516_76CF_S_1.8bit.jp2

paolo · « **Reply #1340 on:** December 25, 2019, 04:45:26 PM »

By the time I write this post, maybe the iceberg has already cracked and this post is obsolete, but I wanted to visualize with three animations zooming the critical points :

A) Cork & SWT-SIS joint (Sentinel 2 images, from 07/12 and 23/12; no alignment on a component of the image to show the actual current movements and their speed over 16 days, the scale is provided in the image)

B) Cork & future iceberg junction (Sentinel 2 images, dated 07/12 and 23/12; no alignment on a component of the image to show the actual current movements and their speed over 16 days (about 6 km!), the scale is provided in the image)

C) component of the future iceberg connected to the Cork (Sentinel 1, 13/12 and 25/12 images; alignment on the future (current?) iceberg)

Points A and C are the most critical and relative to them point B seems stronger.

For animation and zooming click twice

Once one of these points has broken the others will react in an unpredictable way: they could break immediately in their turn, as if the tensions were to be released for a few more days.

The east side of the iceberg will remain attached, but for how long: days or weeks?
The iceberg itself is very fractured and may break very quickly into a thousand pieces.
The part between the two rifts (R1 and R2) should collapse very quickly.

It will be to be followed:
- The third rift (R3) which opened up recently upstream.
- the future iceberg SWT_SIS
- the future of "Cork": will it remain attached for a while to the SIS or will it be swept away with the iceberg?

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

Stephan · « **Reply #1341 on:** December 25, 2019, 07:30:42 PM »

PIIS has really sped up. In EOSDIS Worldview, using the "comparison mode" you can see the movement between Dec 23 and Dec 25. This effect has not been visible in November (17 and 19, 2019).

paolo · « **Reply #1342 on:** December 25, 2019, 08:26:53 PM »

To avoid any ambiguity, I will use the notation of Shean et al. 2019 (see for example the first 'image attached to post 1284) by noting Main Ice Shelf (MIS) the contribution of the PIG to the PIIS and I hope that this will suit all of you and that this will not upset you: I therefore now strictly reserve "PIG" to the grounded part of the glacier and "PIIS" to the whole Ice Shelf, i.e. NIS+MIS+SIS.

Stephan,

Be careful, by chance the speed of the MIS is not the speed of the front, which corresponds roughly to the speed of the MIS + the rate of widening of two rifts (R1 and R2; the most important contribution being that of R2).

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

Stephan · « **Reply #1343 on:** December 25, 2019, 09:05:29 PM »

Paolo,
thank you for that clarification. Of course the speed of the calving front is the sum of the whole ice shelf plus the extra movement caused by the widening of the rifts. This is what I wanted to point out with my posting - the widening of the rifts (EOSDIS can't tell which one has the largest impact) is accelerating.

[I am a little bit of impatiently waiting for the major calving, although I know this is not good for the future of the PIIS]

blumenkraft · « **Reply #1344 on:** December 25, 2019, 09:13:14 PM »

This R3 growth concerns me. Will this part break up with the big calving too? That would be disastrous...

KiwiGriff · « **Reply #1345 on:** December 25, 2019, 10:59:23 PM »

[I am a little bit of impatiently waiting for the major calving, although I know this is not good for the future of the PIIS]

I have seen a train crash.
This is slower but will have the same effect .

Thanks to all the contributors on this thread for your dedication to keeping us informed.

paolo · « **Reply #1346 on:** December 25, 2019, 11:02:35 PM »

Blumenkraft,

In fact, as a result of the existing tensions, a new fracture has been created which extends R3, which is currently still disjunct, and a parallel fracture system between the two and R2. This seems to indicate the existing tensions on the one hand and on the other hand the existence of a more solid sector, which for the time being resists, between R3 and its extension. I have no idea what can happen after calving: either the tensions, even if alleviated, continue, and then we may see a second calving in a few months, or the extension of this rift stops temporarily and then we won't talk again in a year. It is true that it was created very recently (it was not detectable in the image of the 14/09, but only in the image of the 24/10, post 1071), and it already covers a quarter of the width of the MIS (Main Ice Shelf) which is not at all calming.

But there is good news:
- the other two lateral rifts further upstream (still SSM) are no longer spreading, the tensions that generated them are no longer there (but no false hope either, they will reactivate in the months to come).
- no new central rifts detectable

What scares me:
- the possibility that the Cork will not stay in place temporarily during calving and that the dense mixture of ice behind it (mini icebergs) will empty quickly (without creating obstructions which will slow down, at least temporarily, the emptying.
- the possibility that at calving, the NIS area corresponding to the current pinning point will give way and that, as a result, the pinning point will recede consistently upstream

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

blumenkraft · « **Reply #1347 on:** December 26, 2019, 09:13:45 AM »

Thanks, Paolo. I agree.

blumenkraft · « **Reply #1348 on:** December 26, 2019, 01:51:44 PM »

I think no one reported on this yet.

Stephan · « **Reply #1349 on:** December 26, 2019, 03:16:08 PM »

No, I haven't had a look on the Northern Ice Shelf. Thanks for posting.

News:

Author Topic: Pine Island Glacier (PIG) Calving and Discussion (Read 744821 times)

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